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Purpose.To reveal drought resistance ofhybrid tea rosevarieties of garden group in field and laboratory conditions. Methods.Field, biometric, laboratory, statistical. The drought resistance of plants in the field was assessed according to S. S. Pyatnitsky 6-point scale (1961); experiments in the laboratory were to determine the water hol­ding capacity of leaves, their water deficiency, the ability to restore turgor, hydration of tissues according to the unified method of the Institute of Horticulture NAAS (Kytaiev et al., 1998, 2009). Results.According to visual observations in periods with low moisture supply, leaf turgor did not decrease, so in the field, drought resistance ofhybrid tea roseswas estimated at 5 points on a 6-point scale. In the laboratory, water deficiency in the leaves was calculated (as a percentage of the total water content in the state of full saturation). According to the indicators of the water-holding capacity of leaf tissues, varieties with the level of moisture loss in the exposure after 12 hours from the lowest to the highest, were selected. Conclusions.All varieties of hybrid tea roses from the collection of M. M. Gryshko NBG of NAS of Ukraine, included in the experiment, in field conditions were rather drought-resistant. According to the indicators of drought resistance of leaves from 44 model varieties, 9 with low (up to 22.30%), 5 with medium (up to 24.37%), 30 with high and very high level of moisture loss were identified (27.23–46.47%). Analysis of the research results shows that the physiological processes associated with water loss are a variety-specific, genetically inherited trait. Varieties ofhybrid tearoses of diffe­rent geographical origin, which showed the criterion of drought resistance from medium to highest, can be recommended for cultivation in the Right-Bank Forest-Steppe of Ukraine.

Succulence is an adaptation to low water availability characterised by the presence of water-storage tissues that alleviate water stress under low water availability. The succulent syndrome has evolved convergently in over 80 plant families and is associated with anatomical, physiological and biochemical traits. Despite the alleged importance of cell wall traits in drought responses, their significance in the succulent syndrome has long been overlooked. Here, by analysing published pressure–volume curves, we show that elastic adjustment, whereby plants change cell wall elasticity, is uniquely beneficial to succulents for avoiding turgor loss. In addition, we used comprehensive microarray polymer profiling (CoMPP) to assess the biochemical composition of cell walls in leaves. Across phylogenetically diverse species, we uncover several differences in cell wall biochemistry between succulent and non-succulent leaves, pointing to the existence of a ‘succulent glycome’. We also highlight the glycomic diversity among succulent plants, with some glycomic features being restricted to certain succulent lineages. In conclusion, we suggest that cell wall biomechanics and biochemistry should be considered among the characteristic traits that make up the succulent syndrome.

Why this research Matters The inner bark plays important roles in tree stems, including radial exchange of water with the xylem and translocation of carbohydrates. Both processes affect the water content and the thickness of the inner bark on a diurnal basis. For the first time, we simultaneously measured the diurnal variations in the inner bark thickness of hinoki cypress (Chamaecyparis obtusa) by using point dendrometers and those of local xylem potential by using stem psychrometers located next to the dendrometers to determine how these variations were related to each other, to phloem turgor and carbohydrate transport. We also estimated the axial hydrostatic pressure gradient by measuring the osmolality of the sap extracted from the inner bark. The inner bark shrunk during the day and swelled during the night with an amplitude related to day‐to‐day and seasonal variations in climate. The relationship between changes in xylem water potential and inner bark thickness exhibited a hysteresis loop during the day with a median lag of 2 h. A phloem turgor‐related signal can be retrieved from the diurnal variations in the inner bark thickness, which was higher at the upper than at the lower position along the trunk. However, a downward hydrostatic pressure gradient was only observed at dawn, suggesting diurnal variations in the phloem sap flow velocity.

Premise Whether drought‐adaptation mechanisms tend to evolve together, evolve independently, or evolve constrained by genetic architecture is incompletely resolved, particularly for water‐relations traits besides gas exchange. We addressed this issue in two subspecies of Clarkia xantiana (Onagraceae), California winter annuals that separated approximately 65,000 years ago and are adapted, partly by differences in flowering time, to native ranges differing in precipitation. Methods In these subspecies and in recombinant inbred lines (RILs) from a cross between them, we scored traits related to drought adaptation (timing of seed germination and of flowering, succulence, pressure–volume curve variables) in common environments. Results The subspecies native to more arid environments (parviflora) exhibited slower seed germination in saturated conditions, earlier flowering, and greater succulence, likely indicating superior drought avoidance, drought escape, and dehydration resistance via water storage. The other subspecies (xantiana) had lower osmotic potential at full turgor and lower water potential at turgor loss, implying superior dehydration tolerance. Genetic correlations among RILs suggest facilitated evolution of some trait combinations and independence of others. Where genetic correlations exist, subspecies differences fell along them, with the exception of differences in succulence and turgor loss point. In that case, subspecies difference overcame genetic correlations, possibly reflecting strong selection and/or antagonistic genetic correlations with other traits. Conclusions Clarkia xantiana subspecies’ differ in multiple mechanisms of drought adaptation. Genetic architecture generally does not seem to have constrained the evolution of these mechanisms, and it may have facilitated the evolution of some of trait combinations.

Pre-anthesis drought is expected to greatly increase yield losses in wheat (Triticum aestivum L.), one of the most important crops worldwide. Most studies investigate the effects of pre-anthesis drought only at maturity. The physiology of the plant before anthesis and how it is affected during drought is less studied. Our study focused on physiological patterns in wheat plants during pre- and post-anthesis drought. To this end, we measured leaf xylem water potential, osmotic potential and water content in different plant parts at a high temporal frequency: every 3 days, three times a day. The experiment started just before booting until 2 weeks after flowering. Drought stress was induced by withholding irrigation with rewatering upon turgor loss, which occurred once before and once after anthesis. The goal was to investigate the patterns of osmotic adjustment, when it is used for protection against drought, and if the strategy changes during the phenological development of the plant. Our data gave no indication of daily osmotic adjustment, but did show a delicate control of the osmotic potential during drought in both leaves and stem. Under high drought stress, osmotic potential decreased to avoid further water loss. Before anthesis, rewatering restored leaf water potential and osmotic potential quickly. After anthesis, rewatering restored water potential in the flag leaves, but the osmotic potential in the stem and flag leaf remained low longer. Osmotic adjustment was thus maintained longer after anthesis, showing that the plants invest more energy in the osmotic adjustment after anthesis than before anthesis. We hypothesize that this is because the plants consider the developing ear after anthesis a more important carbohydrate sink than the stem, which is a carbohydrate sink before anthesis, to be used later as a reserve. Low osmotic potential in the stem allowed turgor maintenance, while the low osmotic potential in the flag leaf led to an increase in leaf turgor beyond the level of the control plants. This allowed leaf functioning under drought and assured that water was redirected to the flag leaf and not used to refill the stem storage.

В данной работе двумя независимыми способами (1 – с использованием растворов сульфата меди (II) и гексацианоферрата (II) калия; 2 – с использованием раствора силикатных солей и хлорного железа) была получена искусственная полупроницаемая мембрана  модель живой растительной клетки (клеточка Траубе). Показана возможность использования данной модели для наглядных экспериментов на лекциях естественно-научного цикла с целью демонстрации сущности осмотических процессов и проведения экспериментов взаимодействию живых клеток с физиологическими растворами разной концентрации. Установлено, что синтез модельной клетки Траубе с применением водного раствора смеси силикатов и кристаллов хлорного железа более доступно и безопасно для школьников, иностранных учащихся на этапе довузовской подготовки, студентов, по сравнению с использованием для этих целей сульфата меди (II) и гексацианоферрата (II) калия при самостоятельном проведении учащимися данного эксперимента. Проведение таких опытов будет способствовать успешному усвоению ими химии и биологии., In this article, an artificial semipermeable membrane model of a living plant cell (Traube cell) was obtained by two independent methods (1 – using solutions of copper (II) sulfate and potassium hexacyanoferrate (II); 2 – using a solution of silicate salts and ferric chloride). The article demonstrates the possibility of using this model for visual experiments at lectures of the natural science cycle in order to demonstrate the essence of osmotic processes and conduct experiments on the interaction of living cells with physiological solutions of different concentrations. It was found that the synthesis of a model Traube cell using an aqueous solution of a mixture of silicates and ferric chloride crystals is more accessible and safe for schoolchildren, foreign students at the stage of pre-university training, students, compared with the use of copper (II) sulfate and potassium hexacyanoferrate (II) for these purposes when students independently conduct this experiment. Conducting such experiments will contribute to their successful comprehension of chemistry and biology., Международный научно-исследовательский журнал, Выпуск 3 (117) 2022, Pages 21-24

Purpose. To reveal drought resistance of hybrid tea rose varieties of garden group in field and laboratory conditions. Methods. Field, biometric, laboratory, statistical. The drought resistance of plants in the field was assessed according to S. S. Pyatnitsky 6-point scale (1961); experiments in the laboratory were to determine the water hol­ding capacity of leaves, their water deficiency, the ability to restore turgor, hydration of tissues according to the unified method of the Institute of Horticulture NAAS (Kytaiev et al., 1998, 2009). Results. According to visual observations in periods with low moisture supply, leaf turgor did not decrease, so in the field, drought resistance of hybrid tea roses was estimated at 5 points on a 6-point scale. In the laboratory, water deficiency in the leaves was calculated (as a percentage of the total water content in the state of full saturation). According to the indicators of the water-holding capacity of leaf tissues, varieties with the level of moisture loss in the exposure after 12 hours from the lowest to the highest, were selected. Conclusions. All varieties of hybrid tea roses from the collection of M. M. Gryshko NBG of NAS of Ukraine, included in the experiment, in field conditions were rather drought-resistant. According to the indicators of drought resistance of leaves from 44 model varieties, 9 with low (up to 22.30%), 5 with medium (up to 24.37%), 30 with high and very high level of moisture loss were identified (27.23–46.47%). Analysis of the research results shows that the physiological processes associated with water loss are a variety-specific, genetically inherited trait. Varieties of hybrid tea roses of diffe­rent geographical origin, which showed the criterion of drought resistance from medium to highest, can be recommended for cultivation in the Right-Bank Forest-Steppe of Ukraine., Мета. Установити посухостійкість сортів троянд чайно-гібридної садової групи у польових і лабораторних умовах. Методи. Польовий, біометричний, лабораторний, статистичний. Посухостійкість рослин у польових умовах оцінювали за 6-баловою шкалою С. С. П’ятницького (1961), досліди в лабораторних умовах полягали у визначенні водоутримувальної спроможності листків, їх водного дефіциту, здатності відновлювати тургор, оводненості тканин за уніфікованою методикою Інституту садівництва НААН (Китаєв та ін., 1998, 2009). Результати. За візуальними спостереженнями в періоди з низьким рівнем вологозабезпечення тургор листків не знижувався, тож у польових умовах посухостійкість сортів чайно-гібридних троянд оцінено у 5 балів за 6-баловою шкалою. У лабораторних умовах вираховували водний дефіцит у листках (у відсотках від загального вмісту води в стані повного насичення). За показниками водоутримувальної здатності тканин листків сортів чайно-гібридних троянд, виділено сорти з рівнем втрати вологи в експозиції через 12 годин – від найнижчого до найвищого. Висновки. Усі сорти чайно-гібридних троянд колекції НБС ім. М. М. Гришка НАН України, які були у досліді, в польових умовах є достатньо посухостійкими. За показниками посухостійкості листків із 44-х модельних сортів виділено 9 із низьким (до 22,30%), 5 – із середнім (до 24,37%), 30 – з високим і дуже високим (27,23–46,47%) рівнем утрати вологи. Аналіз отриманих результатів досліджень свідчить про те, що фізіологічні процеси, пов’язані з утратою вологи є сортоспецифічною, генетично спадковою ознакою. Сорти чайно-гібридних троянд різного географічного походження, що показали критерій посухостійкості від середнього до найвищого, можна рекомендувати для вирощування в умовах Правобережного Лісостепу України

Presentación de la conferencia invitada en el BP2021: XXIV Reunión de la Sociedad Española de Biología de Plantas y XVII Congreso Hispano-Luso de Biología de Plantas, 7 y 8 de julio de 2021. online, Successful growth, both vegetative and reproductive, are the final goals for plants. In the case of erops, knowing how plants make use of the available resourees to convert them into biomass, and espeeially, what is the main limiting factor for growth, is of paramount importanee. Although much effort has been dedieated to study how different agronomieal practices affect crop water relations and leaf gas exchange, we still lack the knowledge on the precise conditions that favour or limit plant growth. The classieal view, shared among most seientists, is that earbon limit plant growth. This coneeption makes sense sinee photoassimilates are the brieks to build the biomass. However, other proeesses are as important as C02 uptake. In particular, the maintenance of turgor is as critical for growing as photosynthesis. This misconception on the key limiting factor for growth, giving a major role to the souree aetivity instead of the sink aetivity, has emerged from the limitation and availability ofteehnical methods to evaluate both. In our researeh group we have developed novel methods to overcome these limitations, and we have made them suitable for their use under fieId conditions and long period of time during the growing season. Our results confirrn some opinions found in the literature and support, now with empirical evidence, that photosynlhesis, in most cases, is not lhe main limiting factor for growth but turgor. The new coneept "hours of turgor" emerges and will help us understand the perfonnanee of a speeies under a given environment and the funetional physiological traits thal make the difference in growth among species., This research was supported by Spanish Ministry of Scienee, Innovation and Universities (research project AGL2015-71585-R). A.P-A was the recipient of a contract from FPI-CSIC program (Spain).

Fertilization of high-yield apple cultivars leads to increases in hydraulic efficiency and decreases in embolism resistance, as well as drought tolerance of leaves, whereby the influence is highly cultivar specific., Fertilization of woody plants plays a central role in agriculture and forestry, but little is known about how plant water relations are thereby affected. Here we investigated the impact of fertilization on tree hydraulics, and xylem and pit anatomy in the high-yield apple cultivars Golden and Red Delicious. In fertilized trees of Golden Delicious, specific hydraulic conductivity of branch xylem, hydraulic conductance of the root system, and maximum stomatal conductance increased considerably. In Red Delicious, differences between fertilized and control trees were less pronounced. In both cultivars, xylem embolism resistance of fertilized trees was significantly lower and stomatal closure occurred at lower water potentials. Furthermore, water potential at turgor loss point and osmotic potential at full saturation were higher and cell wall elasticity was lower in fertilized plants, suggesting reduced drought tolerance of leaves. Anatomical differences were observed regarding conduit diameters, cell wall reinforcement, pit membrane thickness, pit chamber depth, and stomatal pore length, with more pronounced differences in Golden Delicious. The findings reveal altered hydraulic behaviour in both apple cultivars upon fertilization. The increased vulnerability to hydraulic failure might pose a considerable risk for apple productivity under a changing climate, which should be considered for future cultivation and management practices.

Research Highlights: Our results provide novel perspectives on the effectiveness and collapse of compensatory mechanisms of tracheid development of Norway spruce during intra-seasonal drought and the environmental control of intra-annual density fluctuations. Background and Objectives: This study aimed to compare and integrate complementary methods for investigating intra-annual wood formation dynamics to gain a better understanding of the endogenous and environmental control of tree-ring development and the impact of anticipated climatic changes on forest growth and productivity. Materials and Methods: We performed an integrated analysis of xylogenesis observations, quantitative wood anatomy, and point-dendrometer measurements of Norway spruce (Picea abies (L.) Karst.) trees growing along an elevational gradient in South-western Germany during a growing season with an anomalous dry June followed by an extraordinary humid July. Results: Strong endogenous control of tree-ring formation was suggested at the highest elevation where the decreasing rates of tracheid enlargement and wall thickening during drought were effectively compensated by increased cell differentiation duration. A shift to environmental control of tree-ring formation during drought was indicated at the lowest elevation, where we detected absence of compensatory mechanisms, eventually stimulating the formation of an intra-annual density fluctuation. Transient drought stress in June also led to bimodal patterns and decreasing daily rates of stem radial displacement, radial xylem growth, and woody biomass production. Comparing xylogenesis data with dendrometer measurements showed ambivalent results and it appears that, with decreasing daily rates of radial xylem growth, the signal-to-noise ratio in dendrometer time series between growth and fluctuations of tree water status becomes increasingly detrimental. Conclusions: Our study provides new perspectives into the complex interplay between rates and durations of tracheid development during dry-wet cycles, and, thereby, contributes to an improved and mechanistic understanding of the environmental control of wood formation processes, leading to the formation of intra-annual density fluctuations in tree-rings of Norway spruce.

Chloride (Cl-), traditionally considered harmful for agriculture, has recently been defined as a beneficial macronutrient with specific roles that result in more efficient use of water (WUE), nitrogen (NUE), and CO2 in well-watered plants. When supplied in a beneficial range of 1-5 mM, Cl- increases leaf cell size, improves leaf osmoregulation, and reduces water consumption without impairing photosynthetic efficiency, resulting in overall higher WUE. Thus, adequate management of Cl- nutrition arises as a potential strategy to increase the ability of plants to withstand water deficit. To study the relationship between Cl- nutrition and drought resistance, tobacco plants treated with 0.5-5 mM Cl- salts were subjected to sustained water deficit (WD; 60% field capacity) and water deprivation/rehydration treatments, in comparison with plants treated with equivalent concentrations of nitrate, sulfate, and phosphate salts. The results showed that Cl- application reduced stress symptoms and improved plant growth during water deficit. Drought resistance promoted by Cl- nutrition resulted from the simultaneous occurrence of water deficit avoidance and tolerance mechanisms, which improved leaf turgor, water balance, photosynthesis performance, and WUE. Thus, it is proposed that beneficial Cl- levels increase the ability of crops to withstand drought, promoting a more sustainable and resilient agriculture. Ministerio de Ciencia, Innovación y Universidades AGL2015-71386-R, RTI2018- 094460-B-I00 European Union 895613

16 páginas.- 6 figuras.- 1 tablas.- referencias.. The following supplementary data are available at JXB online..- We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)., Chloride (Cl−), traditionally considered harmful for agriculture, has recently been defined as a beneficial macronutrient with specific roles that result in more efficient use of water (WUE), nitrogen (NUE), and CO2 in well-watered plants. When supplied in a beneficial range of 1–5 mM, Cl− increases leaf cell size, improves leaf osmoregulation, and reduces water consumption without impairing photosynthetic efficiency, resulting in overall higher WUE. Thus, adequate management of Cl− nutrition arises as a potential strategy to increase the ability of plants to withstand water deficit. To study the relationship between Cl− nutrition and drought resistance, tobacco plants treated with 0.5–5 mM Cl− salts were subjected to sustained water deficit (WD; 60% field capacity) and water deprivation/rehydration treatments, in comparison with plants treated with equivalent concentrations of nitrate, sulfate, and phosphate salts. The results showed that Cl− application reduced stress symptoms and improved plant growth during water deficit. Drought resistance promoted by Cl− nutrition resulted from the simultaneous occurrence of water deficit avoidance and tolerance mechanisms, which improved leaf turgor, water balance, photosynthesis performance, and WUE. Thus, it is proposed that beneficial Cl− levels increase the ability of crops to withstand drought, promoting a more sustainable and resilient agriculture., This work was supported by Spanish Ministry of Science Innovation and Universities-FEDER grants AGL2015-71386-R and RTI2018-094460-B-I00, Spanish National Research Council grants CSIC-201840E132, CSIC-201940E039, and CSIC-201940E077, and the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 895613., We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

For more than ten years, Central Chile has faced drought conditions, which impact crop production and quality, increasing food security risk. Under this scenario, implementing management practices that allow increasing water use efficiency is urgent. The study was carried out on kiwifruit trees, located in the O&rsquo, Higgins region, Chile for season 2018&ndash, 2019 and 2019&ndash, 2020. We evaluate the time-series of nine vegetation indices in the VNIR and SWIR regions derived from Sentinel-2 (A/B) satellites to establish how much variability in the canopy water status there was. Over the study&rsquo, s site, eleven sensors were installed in five trees, which continuously measured the leaf&rsquo, s turgor pressure (Yara Water-Sensor). A strong Spearman&rsquo, s (&rho, ) correlation between turgor pressure and vegetation indices was obtained, having &minus, 0.88 with EVI and &minus, 0.81 with GVMI for season 2018&ndash, 2019, and lower correlation for season 2019&ndash, 2020, reaching &minus, 0.65 with Rededge1 and &minus, 0.66 with EVI. However, the NIR range&rsquo, s indices were influenced by the vegetative development of the crop rather than its water status. The red-edge showed better performance as the vegetative growth did not affect it. It is necessary to expand the study to consider higher variability in kiwifruit&rsquo, s water conditions and incorporate the sensitivity of different wavelengths.

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In contrast to animal cells, plant cells are surrounded by walls and thus, they cannot migrate. Therefore, cell elongation is a fundamental process for plant growth. To facilitate this process, a loosening of the rigid cell wall is required. On the other hand, vacuole size has been shown to correlate with cell size and inhibition of vacuolar expansion limits cell growth. However, the specific role of the vacuole during cell elongation is still not fully resolved. Especially the question whether the vacuole is the leading unit during cellular growth or just passively expands upon water uptake remains to be answered. Here, we review recent findings about the contribution of the vacuole to cell elongation. In addition, we also discuss the connection between cell wall status and vacuolar morphology. In particular, we focus on the question whether vacuolar size is dictated by cell size or vice versa and share our personnel view about the sequential steps during cell elongation.

32 páginas.- 5 figuras.- 3 tablas.- 228 referencias.- (This article belongs to the Special Issue Uptake and Compartmentalisation of Mineral Nutrients in Plants), Chloride (Cl−) has traditionally been considered a micronutrient largely excluded by plants due to its ubiquity and abundance in nature, its antagonism with nitrate (NO3−), and its toxicity when accumulated at high concentrations. In recent years, there has been a paradigm shift in this regard since Cl− has gone from being considered a harmful ion, accidentally absorbed through NO3− transporters, to being considered a beneficial macronutrient whose transport is finely regulated by plants. As a beneficial macronutrient, Cl− determines increased fresh and dry biomass, greater leaf expansion, increased elongation of leaf and root cells, improved water relations, higher mesophyll diffusion to CO2, and better water- and nitrogen-use efficiency. While optimal growth of plants requires the synchronic supply of both Cl− and NO3− molecules, the NO3−/Cl− plant selectivity varies between species and varieties, and in the same plant it can be modified by environmental cues such as water deficit or salinity. Recently, new genes encoding transporters mediating Cl− influx (ZmNPF6.4 and ZmNPF6.6), Cl− efflux (AtSLAH3 and AtSLAH1), and Cl− compartmentalization (AtDTX33, AtDTX35, AtALMT4, and GsCLC2) have been identified and characterized. These transporters have proven to be highly relevant for nutrition, long-distance transport and compartmentalization of Cl−, as well as for cell turgor regulation and stress tolerance in plants, This work was supported by the Spanish Ministry of Science Innovation and Universities-FEDER grant RTI2018-094460-B-I00 and by the Spanish National Research Council Projects CSIC-201840E132 and CSIC-201940E039

Bruise damage in fruit results from cell wall failure and inter-cellular separation. Despite the importance of the micro-mechanics of plant tissue with respect to its integrity, it remains largely unquantified and poorly understood, due to many difficulties during experimental characterization. In this article, a 3D micro-mechanical plant tissue model that is able to model cell rupture and inter-cellular debonding and thus provide more insight into the micro-mechanics was developed. The model is based on the discrete element method (DEM) and represents the tissue as a mass-spring system. Each plant cell is represented as a deformable visco-elastoplastic triangulated mesh under turgor pressure. To model cell wall rupture, it is assumed that a spring connection in the wall breaks at a certain critical stretch ratio and that a ruptured cell is turgorless. The inter-cellular contact model assumes brittle fracture between a cell's node and an adjacent cell's triangle when their bond distance exceeds a critical value. A high-speed tomato fruit cell compression test was simulated and the modelled force-strain curve compares well with the experimental data, including for strains above the elastic limit. By varying the shape of the cell in the compression simulation it was shown that the force-strain curve is highly dependent on the cell shape and thus parameter fitting procedures based on a spherical cell model will be inaccurate. Furthermore, the wall stiffness and thickness showed a positive linear relationship with the force at cell bursting. Besides simulating compression tests of single cells, we also simulated tensile and compression tests on small tissue specimens. Realistic tissue structures of tomato mesocarp tissue were generated by a novel method using DEM simulations of deformable cells in a shrinking cylinder. The cell area, volume and anisotropy distributions of the virtual tissue compared well with micro-CT images of real tomato mesocarp tissue (normalized root mean square error values smaller than 3%). The tissue compression and tensile test simulations demonstrated an important influence of the inter-cellular bonding energy and tissue porosity on the tissue failure characteristics and elastic modulus. ispartof: SOFT MATTER vol:15 issue:16 pages:3362-3378 ispartof: location:England status: published

Potassium is very mobile in plants and is transported across membranes using transporters and channels. It is present in the ionic form K+ in plants. Also, in the form of this ion, K+ is taken up by plants from the soil solution. The uptake is mediated by the transporter HAK5 and by the channel AKT1. The transfer of K+ to the xylem is provided by the channel SKOR and the transporter KUP7. The role of potassium as an osmotically active element is crucial. K+ helps to regulate the amount of water in the cells and thus to maintain the turgor. Turgor is important for maintaining the shape of the plant cells and for its growth. Stomatal guard cells are used as a model system for describing processes related to the K+ osmotic function. Movement of K+ is involved in the regulation of opening and closing of stomata on the principle of turgor changes. Transport of K+ into guard cells is provided by channels KAT1, KAT2, AKT1 and AKT2. On the contrary, K+ release is mediated by the channel GORK on the plasma membrane and TPK1 on the tonoplast. K+ supports also the transport of assimilates in the phloem, where the channel AKT2 plays a role. The osmotic functions of K+ are the main topic of this bachelor thesis, which summarizes current knowledge about transport mechanisms necessary for the function of K+ as osmotically...

As multicellular organisms, plants acquire characteristic shapes through a complex set of biological processes known as morphogenesis. Biochemical signalling underlies much of development, as it allows cells to acquire specific identities based on their position within tissues and organs. However, as growing physical structures, plants, and their constituent cells, also experience internal and external physical forces that can be perceived and can influence key processes such as growth, polarity, and gene expression. This process, which adds another layer of control to growth and development, has important implications for plant morphogenesis. This review provides an overview of recent research into the role of mechanical signals in plant development and aims to show how mechanical signalling can be used, in concert with biochemical signals, as a cue allowing cells and tissues to coordinate their behaviour and to add robustness to developmental processes.

This study aims to identify the histological basis for the extraordinary, fast movement of the style in Marantaceae. Although this explosive pollination mechanism was subject of many studies, quantitative measurements to document volumetric changes have never been conducted. Based on physical parameters and limitations (poroelastic time), the movement itself is by far too fast to be explained by turgor changes solely. Therefore, we address the hypothesis that the style contains elastic structures to store energy allowing the fast movement. We provide an experimental approach in Goeppertia bachemiana to identify histological differences of styles in various states, i.e., steady, unreleased, and released state. Cross and longitudinal sections were used to reconstruct the cell volume in different sectors of the style. Histological data were discussed with respect to a putative water shift (turgor movement) and elastic instabilities that were proposed to explain the style movement of Marantaceae. Current data show, that the upper epidermis is under tensile stress in the unreleased state. After style release, the lower side of the style revealed an enormous water up-take. According to our results, we hypothesize that the fast style movement of G. bachemiana is likely based on an elastically stretched upper epidermis, whereas a “soaking tissue” at the lower side presumably mediates the up curling of the style. The experimental data show that at least for G. bachemiana, physical limitations such as the poroelastic time are suitable parameters to predict movements that are based on elastic instabilities.

The current state of coniferous introduced plants growing on the territory of Uman, Cherkasy region is analyzed. Such representatives are the multi-age trees Pinus nigra and Thuja plicata. The studies were aimed at determining their resistance to arid environmental conditions in summer and to adverse factors in the winter period with generally accepted methods. Studies were conducted during 2015-2017. P.nigra trees during the study period received high drought tolerance scores. In Th. plicata plants observed a partial loss of needles turgor during daylight hours. When evaluating the frost resistance, P. nigra trees of different ages did not have visible damage. Young plants Th. plicata were somewhat more vulnerable to the effects of low temperatures, while no damage was found in mature trees. In general, both species have rather high rates of winter hardiness and drought resistance. This indicates their acclimatization to the given growing conditions. Also, the studied plants tolerate the adverse conditions of the city: dust, smoke, soil compaction. Therefore, it is advisable to use them for landscaping urban areas and personal plots. A feature of these species is that they retain a high decorative effect throughout the year and are good components for creating landscape compositions. Comparing the conditions of the natural distribution range to the conditions of the cultural areas of the studied species, it is possible to state their successful cultivation, which indicates a high ecological plasticity and significant potential of these plants

Vascular epiphytes are a major biomass component of forests across the globe and they contribute to 9% of global vascular plant diversity. To improve our understanding of the whole-plant response of epiphytes to future climate change, we investigated for the first time both individual and combined effects of elevated CO2 (560 ppm) and light on the physiology and growth of two epiphyte species [Tillandsia brachycaulos (CAM) and Phlebodium aureum (C3)] grown for 272 days under controlled conditions. We found that under elevated CO2 the difference in water loss between the light (650 μmol m-2s-1) and shade (130 μmol m-2s-1) treatment was strongly reduced. Stomatal conductance (gs) decreased under elevated CO2, resulting in an approximate 40–45% reduction in water loss over a 24 h day/night period under high light and high CO2 conditions. Under lower light conditions water loss was reduced by approximately 20% for the CAM bromeliad under elevated CO2 and increased by approximately 126% for the C3 fern. Diurnal changes in leaf turgor and water loss rates correlated strong positively under ambient CO2 (400 ppm) and high light conditions. Future predicted increases in atmospheric CO2 are likely to alter plant water-relations in epiphytes, thus reducing the canopy cooling potential of epiphytes to future increases in temperature.

The hydraulic coordination along the water transport pathway helps trees provide adequate water supply to the canopy, ensuring that water deficits are minimized and that stomata remain open for CO2 uptake. We evaluated the stem and leaf hydraulic coordination and the linkages between hydraulic traits and the timing of diurnal depression of photosynthesis across seven evergreen tree species in the southern Andes. There was a positive correlation between stem hydraulic conductivity (ks) and leaf hydraulic conductance (KLeaf) across species. All species had similar maximum photosynthetic rates (Amax). The species with higher ks and KLeaf attained Amax in the morning, whereas the species with lower ks and KLeaf exhibited their Amax in the early afternoon concurrently with turgor loss. These latter species had very negative leaf water potentials, but far from the pressure at which the 88% of leaf hydraulic conductance is lost. Our results suggest that diurnal gas exchange dynamics may be determined by leaf hydraulic vulnerability such that a species more vulnerable to drought restrict water loss and carbon assimilation earlier than species less vulnerable. However, under stronger drought, species with earlier CO2 uptake depression may increase the risk of hydraulic failure, as their safety margins are relatively narrow. Fil: Bucci, Sandra Janet. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina Fil: Carbonell Silletta, Luisina Marta. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina Fil: Garré, Analía. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Departamento de Biología; Argentina Fil: Cavallaro, Agustin. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina Fil: Efron, Samanta Thais. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Arias, Nadia Soledad. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina Fil: Goldstein, Guillermo Hernan. University of Miami; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Scholz, Fabian Gustavo. Universidad Nacional de la Patagonia "San Juan Bosco". Instituto de Biociencias de la Patagonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biociencias de la Patagonia; Argentina

Vascular epiphytes are a major biomass component of forests across the globe and they contribute to 9% of global vascular plant diversity. To improve our understanding of the whole-plant response of epiphytes to future climate change, we investigated for the first time both individual and combined effects of elevated CO2 (560 ppm) and light on the physiology and growth of two epiphyte species [Tillandsia brachycaulos (CAM) and Phlebodium aureum (C3)] grown for 272 days under controlled conditions. We found that under elevated CO2 the difference in water loss between the light (650 μmol m-2s-1) and shade (130 μmol m-2s-1) treatment was strongly reduced. Stomatal conductance (gs) decreased under elevated CO2, resulting in an approximate 40–45% reduction in water loss over a 24 h day/night period under high light and high CO2 conditions. Under lower light conditions water loss was reduced by approximately 20% for the CAM bromeliad under elevated CO2 and increased by approximately 126% for the C3 fern. Diurnal changes in leaf turgor and water loss rates correlated strong positively under ambient CO2 (400 ppm) and high light conditions. Future predicted increases in atmospheric CO2 are likely to alter plant water-relations in epiphytes, thus reducing the canopy cooling potential of epiphytes to future increases in temperature.

This study aims to identify the histological basis for the extraordinary, fast movement of the style in Marantaceae. Although this explosive pollination mechanism was subject of many studies, quantitative measurements to document volumetric changes have never been conducted. Based on physical parameters and limitations (poroelastic time), the movement itself is by far too fast to be explained by turgor changes solely. Therefore, we address the hypothesis that the style contains elastic structures to store energy allowing the fast movement. We provide an experimental approach in Goeppertia bachemiana to identify histological differences of styles in various states, i.e., steady, unreleased, and released state. Cross and longitudinal sections were used to reconstruct the cell volume in different sectors of the style. Histological data were discussed with respect to a putative water shift (turgor movement) and elastic instabilities that were proposed to explain the style movement of Marantaceae. Current data show, that the upper epidermis is under tensile stress in the unreleased state. After style release, the lower side of the style revealed an enormous water up-take. According to our results, we hypothesize that the fast style movement of G. bachemiana is likely based on an elastically stretched upper epidermis, whereas a “soaking tissue” at the lower side presumably mediates the up curling of the style. The experimental data show that at least for G. bachemiana, physical limitations such as the poroelastic time are suitable parameters to predict movements that are based on elastic instabilities.

International audience; 1. Many plant species experience large differences in soil moisture availability within a season, potentially leading to a wide range of leaf water potentials (Psi(LEAF)). In order to decrease the risk of leaf dehydration, among species, there is a continuum ranging from strict control (isohydry) to little control (anisohydry) of minimum Psi(LEAF). 2. In central Texas USA, species are exposed to a range of soil moisture from wet springs to hot, dry summers. There are diverging water management strategies among the four dominant woody species in this system; two of these species are more isohydric (Prosopis glandulosa, Quercus fusiformis) while two others are more anisohydric (Diospyros texana, Juniperus asheii). 3. To maintain leaf turgor and photosynthesis during periods of limited soil moisture, anisohydric species may adjust leaf hydraulic parameters more than isohydric species. To test this hypothesis, we quantified iso/anisohydry from 3 years of Psi(LEAF) predawn and midday measurements, and we measured the changes in turgor loss points (Psi(TLP)), osmotic potential at full hydration (Psi(pi 100)), and resistance to leaf hydraulic dysfunction (leaf P-50) throughout the spring and summer of 2016. 4. Diospyros and Juniperus experienced more negative Psi(LEAF) and adjusted Psi(TLP) and Psi(pi 100) in response to both drying soils during the summer also in response to rainfall events during September. In contrast, the more isohydric species (Quercus and Prosopis) did not appear to adjust Psi(TLP) or Psi(pi 100) in response to soil moisture. The more anisohydric species also adjusted leaf P-50 during periods of reduced soil moisture. 5. Our results suggest that species that experience wider ranges of Psi(LEAF) have a greater ability to alter leaf hydraulic properties. This provides insight on how species with different strategies for water potential regulation may modify properties to mitigate drought effects in the future.

In the filamentous fungus Neurospora crassa, phospholipase C may play a role in hyphal extension at the growing tips as part of a growth-sensing mechanism that activates calcium release from internal stores to mediate continued expansion of the hyphal tip. One candidate for a tip-localized phospholipase C is PLC-1. We characterized morphology and growth characteristics of a knockout mutant (KO plc-1) and a RIP mutated strain (RIP plc-1) (missense mutations and a nonsense mutation render the gene product non-functional). Growth and hyphal cytology of wildtype and KO plc-1 were similar, but the RIP plc-1 mutant grew slower and exhibited abnormal membrane structures at the hyphal tip, imaged using the fluorescence dye FM4-64. To test for causes of the slower growth of the RIP plc-1 mutant, we examined its physiological poise compared to wildtype and the KO plc-1 mutant. The electrical properties of all three strains and the electrogenic contribution of the plasma membrane H+-ATPase (identified by cyanide inhibition) were the same. Responses to high osmolarity were also similar. However, the RIP plc-1 mutant had a significantly lower turgor, a possible cause of its slower growth. While growth of all three strains was inhibited by the phospholipase C inhibitor 3-nitrocoumarin, the RIP plc-1 mutant did not exhibit hyphal bursting after addition of the inhibitor, observed in both wildtype and the KO plc-1 mutant. Although the plc-1 gene is not obligatory for tip growth, the phenotype of the RIP plc-1 mutant – abnormal tip cytology, lower turgor and resistance to inhibitor-induced hyphal bursting – suggest it does play a role in tip growth. The expression of a dysfunctional plc-1 gene may cause a shift to alternative mechanism(s) of growth sensing in hyphal extension.

Results of researches of various cultivars and hybrids of tangerine growing in the conditions of the humid subtropics of Russia and possessing valuable physiological and biochemical markers are presented in article. The stress factors limiting cultivation of tangerine culture in Krasnodar region are defined. The assessment of the water saving and enzymes activity in tangerine leaves is given. Changes of physiological parameters at influence of a stressful factor are shown. The analysis of water deficiency is revealed existence of essential distinctions between cultivars and hybrids. Change of thickness of a leaf blade of tangerine is the important diagnostic characteristic testifying the ability of leaf tissues to accumulate and keep water. Researches are showing that difference between catalase action of cultivars and hybrids are insignificant. Strengthening of enzyme activity can testify to bigger violation of a functional state of plant cultivars in comparison with the hybrides. Water deficiency and drought resistance coefficient can be used for diagnostics of stability of tangerine to hydrothermal factors. Correlation coefficients between the studied markers were calculated and regression models of their interrelation were given. So, there was a high correlation between thickness of a leaf blade and water deficiency index; close correlation between water deficiency and thickness of a leaf blade, as well as dependence of average degree on water deficiency and catalase activity were noted. There were revealed tangerine cultivars and hybrids which are stable in in the changing environmental conditions and have high biochemical value of fruits.

Leaf photosynthesis relies on CO2 diffusing in while water vapour diffuses out. When stomata close, cuticle waxes on the epidermal tissues increasingly affect this diffusion. Also, changes in turgor can shrink or swell a leaf, varying the cuticle size. In this study, the properties of the cuticle were investigated while turgor varied in intact leaves of hypo stomatous grape (Vitis vinifera L.) or amphistomatous sunflower (Helianthus annuus L.). For grape, stomata on the abaxial surface were sealed and high CO2 concentrations outside the leaf were used to maximize diffusion through the adaxial, stoma-free cuticle. For sunflower, stomata were closed in the dark or with abscisic acid to maximize the cuticle contribution to the path. In both species, the internal CO2 concentration was measured directly and continuously while other variables were determined to establish the cuticle properties. The results indicated that stomatal closure diminished the diffusion of both gases in both species, but for CO2 more than for water vapour. Decreasing the turgor diminished the movement of both gases through the cuticle of both species. Because this turgor effect was observed in the adaxial surface of grape, which had no stomata, it could only be attributed to cuticle tightening. Comparing calculated and measured concentrations of CO2 in leaves revealed differences that became large as stomata began to close. These differences in transport, together with turgor effects, suggest calculations of the CO2 concentration inside leaves need to be viewed with caution when stomata begin to close.

Circadian leaf movements are widely known in plants, but nocturnal movement of treebranches were only recently discovered by using terrestrial laser scanning (TLS), a highresolution three-dimensional surveying technique. TLS uses a pulsed laser emitted in aregular scan pattern for rapid measurement of distances to the targets, thus producingthree dimensional point cloud models of sub-centimeter resolution and accuracy in a fewminutes. Here, we aimto gain an overview of the variability of circadianmovement of smalltrees across different taxonomic groups, growth forms and leaf anatomies. We surveyeda series of 18 full scans over a 12-h night period to measure nocturnal changes in shapesimultaneously for an experimental setup of 22 plants representing different species.Resulting point clouds were evaluated by comparing changes in height percentiles oflaser scanning points belonging to the canopy. Changes in crown shape were observedfor all studied trees, but clearly distinguishable sleep movements are apparently rare.Ambient light conditions were continuously dark between sunset (7:30 p.m.) and sunrise(6:00 a.m.), but most changes in movement direction occurred during this period, thusmost of the recorded changes in crown shape were probably not controlled by ambientlight. The highest movement amplitudes, for periodic circadian movement around 2 cmwere observed for Aesculus and Acer, compared to non-periodic continuous change inshape of 5 cm for Gleditschia and 2 cm for Fargesia. In several species we detected2–4 h cycles of minor crown movement of 0.5–1 cm, which is close to the limit of ourmeasurement accuracy. We present a conceptual framework for interpreting observedchanges as a combination of circadian rhythm with a period close to 12 h, short-termoscillation repeated every 2–4 h, aperiodic continuous movement in one direction andmeasurement noise which we assume to be random. Observed movement patternsare interpreted within this framework, and connections with morphology and taxonomyare proposed. We confirm the existence of overnight “sleep” movement for some trees,but conclude that circadian movement is a variable phenomenon in plants, probablycontrolled by a complex combination of anatomical, physiological, and morphologicalfactors.

Main conclusion Drought-acclimated vines maintained higher gas exchange compared to irrigated controls under water deficit; this effect is associated with modified leaf turgor but not with improved petiole vulnerability to cavitation. A key feature for the prosperity of plants under changing environments is the plasticity of their hydraulic system. In the present research we studied the hydraulic regulation in grapevines (Vitis vinifera L.) that were first acclimated for 39 days to well-watered (WW), sustained water deficit (SD), or transient—cycles of dehydration–rehydration—water deficit (TD) conditions, and then subjected to varying degrees of drought. Vine development under SD led to the smallest leaves and petioles, but the TD vines had the smallest mean xylem vessel and calculated specific conductivity (k ts). Unexpectedly, both the water deficit acclimation treatments resulted in vines more vulnerable to cavitation in comparison to WW, possibly as a result of developmental differences or cavitation fatigue. When exposed to drought, the SD vines maintained the highest stomatal (g s) and leaf conductance (k leaf) under low stem water potential (Ψs), despite their high xylem vulnerability and in agreement with their lower turgor loss point (ΨTLP). These findings suggest that the down-regulation of k leaf and g s is not associated with embolism, and the ability of drought-acclimated vines to maintain hydraulic conductance and gas exchange under stressed conditions is more likely associated with the leaf turgor and membrane permeability. Electronic supplementary material The online version of this article (doi:10.1007/s00425-017-2662-3) contains supplementary material, which is available to authorized users.

International audience; Morphogenesis in plants is directly linked to the mechanical elements of growing tissues, namely cell wall and inner cell pressure. Studies of these structural elements are now often performed using indentation methods such as atomic force microscopy. In these methods, a probe applies a force to the tissue surface at a subcellular scale and its displacement is monitored, yielding force-displacement curves that reflect tissue mechanics. However, the interpretation of these curves is challenging as they may depend not only on the cell probed, but also on neighboring cells, or even on the whole tissue. Here, we build a realistic three-dimensional model of the indentation of a flower bud using SOFA (Simulation Open Framework Architecture), in order to provide a framework for the analysis of force-displacement curves obtained experimentally. We find that the shape of indentation curves mostly depends on the ratio between cell pressure and wall modulus. Hysteresis in force-displacement curves can be accounted for by a viscoelastic behavior of the cell wall. We consider differences in elastic modulus between cell layers and we show that, according to the location of indentation and to the size of the probe, force-displacement curves are sensitive with different weights to the mechanical components of the two most external cell layers. Our results confirm most of the interpretations of previous experiments and provide a guide to future experimental work.

Under the drought stress condition, the plants would grow slower. Temperature is one of the most important abiotic factors which suppress the germination processes. However, the processes of transpiration are regulated directly by the cell water, which followed to an increase in volume of vacuoles. During stretching under the influence of water pressure, the cell goes into the state of turgor. In our experiments, lines of the semi-dental sweet maize of Armenian population from various zones of growth under mild and severe drought stress were tested. According to results, the value of the water balance of the plant cells may reflect the ability of plants to adapt to drought stress. It can be assumed that the turgor allows evaluating the number of received dissolved substance in cell., {"references":["D.J. Cosgrove, Z.C. Li \"Role of expansion in cell enlargement of oat coleoptiles (analysis of developmental gradients and photo control)\". Plant Physiol. 1993, 103, 1321–1328.","E.A. Bray, J. Bailey-Serres, E. Weretilnyk \"Responses to abiotic stresses\". In W Gruissem, B Buchannan, R Jones, ets, Biochemistry and Molecular Biology of Plants. American Society of Plant Physiologists, Rockville, 2000, pp. 1158–1249.","P. Xianjun, M. Xingyong, F. Weihong, etc \"Improved drought and salt tolerance of Arabidopsis thaliana by transgenic expression of a novel DREB gene from Leymuschinensis\". Plant Cell Rep., 2011 Aug; 30(8), pp. 1493-502.","F. Tardieu \"Any trait or trait-related allele can confer drought tolerance: Just design the right drought scenario\". J. Exp. Bot. 2011, vol. 63, pp.25–31.","S. Wolf, S. Greiner \"Growth control by cell wall pectins\". Protoplasma 2012, 249, pp. 169–175.","F. Tardieu, B. Parent, C.F. Caldeira, C. Welcker\"Genetic and physiological controls of growth under water deficit\". Plant Physiol. 2014, 164, pp.1628–1635.","V. Stoppin-Mellet, J. Gaillard, M. Vantard \"Functional evidence for in vitro microtubule severing by the plant katanin homologue\". Biochem J. 2002, 365, pp. 337–342.","M. Uyttewaal, A. Burian, K.Alim, B. Landrein, D. Borowska-Wykręt, et al. \"Mechanical stress acts via katanin to amplifydifferences in growth rate between adjacent cells in Arabidopsis\". Cell 2012, 149, pp. 439–451.","H.-B. Shao, L.-Y. Chu, C.A. Jaleel, C.-X. Zhao \"Water-deficit stress-induced anatomical changes in higher plants\". C. R. Biol. 2008, 331, pp. 215–225.\n[10]\tS.Y.S. Lisar, R. Motafakkerazad, M.M. Hossain, I.M.M. Rahman \"Water stress in plants: Causes, effects and responses\". In Water Stress; M. Rahman, H. Hasegawa, Eds.; InTech: Rijeka, Croatia, 2012; pp. 1–14.\n[11]\tM. Benešová, D. Holá, L. Fischer \"The Physiology and Proteomics of Drought Tolerance in Maize: Early Stomatal Closure as a Cause of Lower Tolerance to Short-Term Dehydration?\".DOI: 10.1371/journal.pone.0038017\n[12]\tCruz de Carvalho, Maria Helena \"Drought stress and reactive oxygen species\" Plant Signal Behav.March; 3(3), pp. 156–165.\n[13]\tJ.Ingram, D. Bartels D. \"The molecular basis of dehydration tolerance in plants\". AMU Rev Plant Physiol Plant Mol Biol,1996. vol.47, pp. 377-403.\n[14]\tJ. Strable and M. Scanlon \"Maize (Zea mays): A Model Organism for Basicand Applied Research\" Cold Spring Harb Protoc 2009."]}

Previous experiments have demonstrated positive effect of Acadian(®) extract of Ascophyllum nodosum on plant stress-resistance, however the mode of action is not fully understood. The aim of this study was to understand the physiological effect of Acadian(®) seaweed extract on the plant response to drought stress. Leaf temperature and leaf angle were measured as early-stage indicators of plant stress with thermal imaging "in situ" over a 5-day stress-recovery trial. The early stress-response of control became visible on the third day as a rapid wilting of leaves, accompanied with the asymptotic increase of leaf temperature on 4-5 °C to the thermal equilibrium with ambient air temperature. At the same time Acadian(®) treated plants still maintained turgor, accompanied with the linear increase in leaf temperature, which indicated better control of stomatal closure. Re-watering on the fifth day showed better survival of treated plants compared to control. This study demonstrated the ability of Acadian(®) seaweed extract to improve resistance of soybean plants to water stress.

Enzyme-less chemistry appears to control the growth rate of the green alga Chara corallina. The chemistry occurs in the wall where a calcium pectate cycle determines both the rate of wall enlargement and the rate of pectate deposition into the wall. The process is the first to indicate that a wall polymer can control how a plant cell enlarges after exocytosis releases the polymer to the wall. This raises the question of whether other species use a similar mechanism. Chara is one of the closest relatives of the progenitors of terrestrial plants and during the course of evolution, new wall features evolved while pectate remained one of the most conserved components. In addition, charophytes contain auxin which affects Chara in ways resembling its action in terrestrial plants. Therefore, this review considers whether more recently acquired wall features require different mechanisms to explain cell expansion.

19 páginas.-- 9 figuras.-- 5 tablas.-- 77 referencias.-- Supplementary Data: Supplementary_figures_S1_S7___Tables_S1_S7.pdf, Chloride (Cl–) is a micronutrient that accumulates to macronutrient levels since it is normally available in nature and actively taken up by higher plants. Besides a role as an unspecific cell osmoticum, no clear biological roles have been explicitly associated with Cl– when accumulated to macronutrient concentrations. To address this question, the glycophyte tobacco (Nicotiana tabacum L. var. Habana) has been treated with a basal nutrient solution supplemented with one of three salt combinations containing the same cationic balance: Cl–-based (CL), nitrate-based (N), and sulphate+phosphate-based (SP) treatments. Under non-saline conditions (up to 5mM Cl–) and no water limitation, Cl– specifically stimulated higher leaf cell size and led to a moderate increase of plant fresh and dry biomass mainly due to higher shoot expansion. When applied in the 1–5mM range, Cl– played specific roles in regulating leaf osmotic potential and turgor, allowing plants to improve leaf water balance parameters. In addition, Cl– also altered water relations at the whole-plant level through reduction of plant transpiration. This was a consequence of a lower stomatal conductance, which resulted in lower water loss and greater photosynthetic and integrated water-use efficiency. In contrast to Cl–, these effects were not observed for essential anionic macronutrients such as nitrate, sulphate, and phosphate. We propose that the abundant uptake and accumulation of Cl– responds to adaptive functions improving water homeostasis in higher plants., This work was supported by the Spanish Ministry of Science and Innovation-FEDER grant AGL2009-08339/AGR. The help, expertise, and technical assistance of C. Rivero, A. Vázquez, S. Luque, B.J. Sañudo, F.J. Durán, Y. Pinto, and J. Espartero are gratefully acknowledged. We would like to extend our gratitude to the valuable reviews and contributions by the anonymous referees and the editor, Timothy Colmer, which helped us to improve the manuscript substantially.

Stomata are structures in plant epidermis which regulate contact between inner and outer environment of the plant by mediating their stomatal aperture. Many inner and outer signals contribute to the ontogenesis of the stomatal pattern. Guard cells undergo significant change of volume and surface during stomatal movement. This change of surface must be compensated by intracellular trafficking of membrane material because biological membrane has limited elasticity. Most of this trafficking takes place between plasma membrane and endosomal compartments. Complex exocyst is protein complex that ensures proper targeting of secretory vesicles to their destination on the plasma membrane. Function of this complex is essential for many cellular processes that require precise targeting of secretion. Mutation in gene Exo70B1 causes different development of the stomatal pattern. Plants with mutated Exo70B1 differ in stomatal size depending on the cultivation conditions more than wild type plant. Protein EXO70B1 is also directly involved in stomatal dynamics because mutants exo70B1 have retarded stomatal opening in response to light. This direct connection can be observed on the fluorescently labeled protein EXOB1 which significantly changes its localization during stomatal movements. None of these observed phenotypes is...

Salzstress stellt in vielen Regionen der Erde ein wesentliches Problem in der Landwirtschaft dar. Hierbei sind vor allem semiaride Gebiete betroffen, in denen die Verdunstung von Wasser aus dem Boden die Niederschläge übertrifft. Es kommt zu einer Akkumulation von Salz im fruchtbaren Oberboden und führt zu starken Wachstumseinbußen bei Kulturpflanzen (Qadir et al. 2006). Salzstress bei Pflanzen kann in 2 Phasen eingeteilt werden: in einer ersten Phase kommt es zu einer Verminderung des Wachstums durch osmotischen Stress, während es in der zweiten Phase des Salzstress bei empfindlichen Genotypen durch Ionentoxizität zum völligen Erliegen des Wachstums kommt. Salzresistente Genotypen können ihr Wachstum auf einem verminderten Niveau aufrecht erhalten (Munns 1993). Durch gezielte Kreuzung von osmotisch resistenten Maislinien mit einer Natrium exkludierenden Inzuchtlinie (NaExIl) konnten Hybriden (SR-Hybriden) erstellt werden, die sowohl in der ersten, als auch in der zweiten Phase des Salzstresses eine erhöhte Resistenz aufweisen (Schubert 2006). Die Resistenz in der ersten Phase des Salzstresses wird von den ähnlich resistenten Maisgenotypen SR 03 und SR 12 mit unterschiedlichen Strategien erreicht. Während SR 03 unter Salzstress die Ansäuerung der Zellwand und somit das Wachstum aufrecht erhält (Pitann etal. 2009), erhöht SR 12 die Konzentration von Arabinose in der Hemicellulose (Uddin et al. 2013), was zu einer Aufweichung der Zellwand führt. Eine Kombination von aufrecht erhaltener Zellwandansäuerung und erhöhter Arbinosekonzentration sollte zu einer erhöhten Resistenz in der ersten Phase des Salzstresses führen. Dies wurde in dieser Arbeit durch die Kreuzung der Mutterlinien von SR 03 und SR 12 und eine anschließende Erstellung von Doppelhaploiden, welche wiederum mit NaExIl gekreuzt wurden, überprüft. Die hieraus hervorgegangene Hybride DSR 5 zeigte eine erhöhte Resistenz in der ersten Phase des Salzstresses bei gleichzeitiger Aufrechterhaltung der Ansäuerung der Zellwand und einer erhöhten Arabinosekonzentration. Dennoch war die Extensibilität der Zellwand in diesem Genotypen unter Salzstress vermindert. Ein weiterer Faktor, der die Zellwandextensibilität beeinflussen könnte, ist die Konzentration der Cellulose in der Zellwand, die unter Salzstress der ersten Phase vermindert ist (Uddin et al. 2013). Durch eine erhöhte Calciumgabe bei Pioneer 3906 konnte die Konzentration der Cellulose auf das Niveau der Kontrolle wiederhergestellt werden, jedoch war kein Einfluss auf die Zellwandextensibilität feststellbar. Messungen von weiteren resistenten und empfindlichen Genotypen unter Salzstress ergaben unterschiedliche Reaktionen der Zellwandextensibilität auf Salzstress. Es konnte nicht zwischen resistenten und sensitiven Genotypen unterschieden werden. Eine aufrecht erhaltene Zellwandextensibilität ist somit nicht zwingend für eine Resistenz in der ersten Phase des Salzstresses notwendig. Neben der Zellwandextensibilität ist der Turgorschwellenwert ein maßgeblicher Faktor für die Zellstreckung. Dieser wurde durch 100 mM NaCl bei Pioneer 3906 jedoch nicht signifikant verändert und kann somit als begrenzender Faktor unter Salzstress ausgeschlossen werden. Eine weitere Einschränkung des Wachstums liegt in einer verminderten Zellteilung. Die Messung des DNA-Gehaltes im Spross von Pioneer 3906 ergab bei 100 mM NaCl eine um 39,4% verminderte Zellzahl im Vergleich mit Kontrollbedingungen. Dies führt zu der Schlussfolgerung, dass Salzstress durch eine starke Einschränkung der Zellteilung das Wachstum vermindert. Salt stress is a major problem for agriculture in many parts of the world. Especially semiarid regions are affected, where evoporation exceeds precipitation. This leads to an accumulation of salt in fertile upper soils and results in severe growth depressions of crops (Qadir et al. 2006). Salt stress can be separated into two phases: In the first phase of salt stress growth is reduced by osmotic stress. In the second phase ion toxicity leads to a complete collapse of growth in sensitive genotypes while resistant genotypes can maintain growth at a limited level (Munns 1993). By systematic crossing of osmotically resistant maize inbred lines with a newly developed sodium-excluding inbred line (NaExIl) salt-resistant hyrbids (SR-hybrids) were bred. These hybrids show a higher resistance in the first as well as in the second phase of salt stress (Schubert 2006). Resistance in the first phase of salt stress is achieved by the similarly resistant genotypes SR 03 and SR 12 by different strategies. SR 03 maintains growth under salt stress by maintaining acidification of the cell wall (Pitann et al. 2009). SR 12 increases the concentration of arabinose in the hemicellulosic fraction of its cell wall under salt stress (Uddin et al. 2013). Both strategies may lead to a higher cell-wall extensibility under salt stress compared to sensitive genotypes. A combination of these strategies should lead to an increase of salt stress in the first phase. This was tested by crossing of the mother lines of SR 03 and SR 12, and establishment of doubled haploids from their offsprings and crossing these with NaExIl. From the resulting hybrids (DSR hybrids) DSR 5 showed an increase in arabinose and a maintained cell-wall acidification under salt stress. Nevertheless, cell-wall extensibility was reduced. Another factor that may reduce cell-wall extensibility is the reduced cellulose concentration in the cell wall under salt stress (Uddin et al. 2013). Additional calcium in the nutrient solution of Pioneer 3906 led to an increase of cellulose concentration under salt stress compared to the level of control plants. This restoration of cellulose concentration was not related to an increase of cell-wall extensibility. Measurements of different salt-resistant and sensitive maize genotypes yielded different results in the reaction of cell-wall extensibility under salt stress. There is no direct relationship between salt resistance and cell-wall extensibility. Besides cell-wall extensibility the wall-yield threshold is a relevant factor for cell enlargement. But there was no significant change of wall-yield threshold in Pionner 3906 under salt stress compared to control conditions. Another growth-restricting factor is the reduction of cell division. Measurement of DNA content of the shoot of Pioneer 3906 under salt stress resulted in a reduction of cells by 39,4% compared to control conditions. This leads to the conclusion that salt stress severely affects cell division and thus growth.

Salzstress stellt in vielen Regionen der Erde ein wesentliches Problem in der Landwirtschaft dar. Hierbei sind vor allem semiaride Gebiete betroffen, in denen die Verdunstung von Wasser aus dem Boden die Niederschläge übertrifft. Es kommt zu einer Akkumulation von Salz im fruchtbaren Oberboden und führt zu starken Wachstumseinbußen bei Kulturpflanzen (Qadir et al. 2006). Salzstress bei Pflanzen kann in 2 Phasen eingeteilt werden: in einer ersten Phase kommt es zu einer Verminderung des Wachstums durch osmotischen Stress, während es in der zweiten Phase des Salzstress bei empfindlichen Genotypen durch Ionentoxizität zum völligen Erliegen des Wachstums kommt. Salzresistente Genotypen können ihr Wachstum auf einem verminderten Niveau aufrecht erhalten (Munns 1993). Durch gezielte Kreuzung von osmotisch resistenten Maislinien mit einer Natrium exkludierenden Inzuchtlinie (NaExIl) konnten Hybriden (SR-Hybriden) erstellt werden, die sowohl in der ersten, als auch in der zweiten Phase des Salzstresses eine erhöhte Resistenz aufweisen (Schubert 2006). Die Resistenz in der ersten Phase des Salzstresses wird von den ähnlich resistenten Maisgenotypen SR 03 und SR 12 mit unterschiedlichen Strategien erreicht. Während SR 03 unter Salzstress die Ansäuerung der Zellwand und somit das Wachstum aufrecht erhält (Pitann etal. 2009), erhöht SR 12 die Konzentration von Arabinose in der Hemicellulose (Uddin et al. 2013), was zu einer Aufweichung der Zellwand führt. Eine Kombination von aufrecht erhaltener Zellwandansäuerung und erhöhter Arbinosekonzentration sollte zu einer erhöhten Resistenz in der ersten Phase des Salzstresses führen. Dies wurde in dieser Arbeit durch die Kreuzung der Mutterlinien von SR 03 und SR 12 und eine anschließende Erstellung von Doppelhaploiden, welche wiederum mit NaExIl gekreuzt wurden, überprüft. Die hieraus hervorgegangene Hybride DSR 5 zeigte eine erhöhte Resistenz in der ersten Phase des Salzstresses bei gleichzeitiger Aufrechterhaltung der Ansäuerung der Zellwand und einer erhöhten Arabinosekonzentration. Dennoch war die Extensibilität der Zellwand in diesem Genotypen unter Salzstress vermindert. Ein weiterer Faktor, der die Zellwandextensibilität beeinflussen könnte, ist die Konzentration der Cellulose in der Zellwand, die unter Salzstress der ersten Phase vermindert ist (Uddin et al. 2013). Durch eine erhöhte Calciumgabe bei Pioneer 3906 konnte die Konzentration der Cellulose auf das Niveau der Kontrolle wiederhergestellt werden, jedoch war kein Einfluss auf die Zellwandextensibilität feststellbar. Messungen von weiteren resistenten und empfindlichen Genotypen unter Salzstress ergaben unterschiedliche Reaktionen der Zellwandextensibilität auf Salzstress. Es konnte nicht zwischen resistenten und sensitiven Genotypen unterschieden werden. Eine aufrecht erhaltene Zellwandextensibilität ist somit nicht zwingend für eine Resistenz in der ersten Phase des Salzstresses notwendig. Neben der Zellwandextensibilität ist der Turgorschwellenwert ein maßgeblicher Faktor für die Zellstreckung. Dieser wurde durch 100 mM NaCl bei Pioneer 3906 jedoch nicht signifikant verändert und kann somit als begrenzender Faktor unter Salzstress ausgeschlossen werden. Eine weitere Einschränkung des Wachstums liegt in einer verminderten Zellteilung. Die Messung des DNA-Gehaltes im Spross von Pioneer 3906 ergab bei 100 mM NaCl eine um 39,4% verminderte Zellzahl im Vergleich mit Kontrollbedingungen. Dies führt zu der Schlussfolgerung, dass Salzstress durch eine starke Einschränkung der Zellteilung das Wachstum vermindert., Salt stress is a major problem for agriculture in many parts of the world. Especially semiarid regions are affected, where evoporation exceeds precipitation. This leads to an accumulation of salt in fertile upper soils and results in severe growth depressions of crops (Qadir et al. 2006). Salt stress can be separated into two phases: In the first phase of salt stress growth is reduced by osmotic stress. In the second phase ion toxicity leads to a complete collapse of growth in sensitive genotypes while resistant genotypes can maintain growth at a limited level (Munns 1993). By systematic crossing of osmotically resistant maize inbred lines with a newly developed sodium-excluding inbred line (NaExIl) salt-resistant hyrbids (SR-hybrids) were bred. These hybrids show a higher resistance in the first as well as in the second phase of salt stress (Schubert 2006). Resistance in the first phase of salt stress is achieved by the similarly resistant genotypes SR 03 and SR 12 by different strategies. SR 03 maintains growth under salt stress by maintaining acidification of the cell wall (Pitann et al. 2009). SR 12 increases the concentration of arabinose in the hemicellulosic fraction of its cell wall under salt stress (Uddin et al. 2013). Both strategies may lead to a higher cell-wall extensibility under salt stress compared to sensitive genotypes. A combination of these strategies should lead to an increase of salt stress in the first phase. This was tested by crossing of the mother lines of SR 03 and SR 12, and establishment of doubled haploids from their offsprings and crossing these with NaExIl. From the resulting hybrids (DSR hybrids) DSR 5 showed an increase in arabinose and a maintained cell-wall acidification under salt stress. Nevertheless, cell-wall extensibility was reduced. Another factor that may reduce cell-wall extensibility is the reduced cellulose concentration in the cell wall under salt stress (Uddin et al. 2013). Additional calcium in the nutrient solution of Pioneer 3906 led to an increase of cellulose concentration under salt stress compared to the level of control plants. This restoration of cellulose concentration was not related to an increase of cell-wall extensibility. Measurements of different salt-resistant and sensitive maize genotypes yielded different results in the reaction of cell-wall extensibility under salt stress. There is no direct relationship between salt resistance and cell-wall extensibility. Besides cell-wall extensibility the wall-yield threshold is a relevant factor for cell enlargement. But there was no significant change of wall-yield threshold in Pionner 3906 under salt stress compared to control conditions. Another growth-restricting factor is the reduction of cell division. Measurement of DNA content of the shoot of Pioneer 3906 under salt stress resulted in a reduction of cells by 39,4% compared to control conditions. This leads to the conclusion that salt stress severely affects cell division and thus growth.

The two alkali cations Na(+) and K(+) have similar relative abundances in the earth crust but display very different distributions in the biosphere. In all living organisms, K(+) is the major inorganic cation in the cytoplasm, where its concentration (ca. 0.1 M) is usually several times higher than that of Na(+). Accumulation of Na(+) at high concentrations in the cytoplasm results in deleterious effects on cell metabolism, e.g., on photosynthetic activity in plants. Thus, Na(+) is compartmentalized outside the cytoplasm. In plants, it can be accumulated at high concentrations in vacuoles, where it is used as osmoticum. Na(+) is not an essential element in most plants, except in some halophytes. On the other hand, it can be a beneficial element, by replacing K(+) as vacuolar osmoticum for instance. In contrast, K(+) is an essential element. It is involved in electrical neutralization of inorganic and organic anions and macromolecules, pH homeostasis, control of membrane electrical potential, and the regulation of cell osmotic pressure. Through the latter function in plants, it plays a role in turgor-driven cell and organ movements. It is also involved in the activation of enzymes, protein synthesis, cell metabolism, and photosynthesis. Thus, plant growth requires large quantities of K(+) ions that are taken up by roots from the soil solution, and then distributed throughout the plant. The availability of K(+) ions in the soil solution, slowly released by soil particles and clays, is often limiting for optimal growth in most natural ecosystems. In contrast, due to natural salinity or irrigation with poor quality water, detrimental Na(+) concentrations, toxic for all crop species, are present in many soils, representing 6 % to 10 % of the earth's land area. Three families of ion channels (Shaker, TPK/KCO, and TPC) and 3 families of transporters (HAK, HKT, and CPA) have been identified so far as contributing to K(+) and Na(+) transport across the plasmalemma and internal membranes, with high or low ionic selectivity. In the model plant Arabidopsis thaliana, these families gather at least 70 members. Coordination of the activities of these systems, at the cell and whole plant levels, ensures plant K(+) nutrition, use of Na(+) as a beneficial element, and adaptation to saline conditions.

TreeWatch.net is an initiative that has been developed to watch trees grow and function in real-time. It is a water- and carbon-monitoring and modeling network, in which high-quality measurements of sap flow and stem diameter variation are collected on individual trees. Automated data processing using a cloud service enables instant visualization of water movement and radial stem growth. This can be used to demonstrate the sensitivity of trees to changing weather conditions, such as drought, heat waves, or heavy rain showers. But TreeWatch.net’s true innovation lies in its use of these high-precision harmonized data to also parameterize process-based tree models in real-time, which makes displaying the much-needed mechanisms underlying tree responses to climate change possible. Continuous simulation of turgor to describe growth processes and long-term time series of hydraulic resistance to assess drought-vulnerability in real-time are only a few of the opportunities our approach offers. TreeWatch.net has been developed with the view to be complementary to existing forest monitoring networks and with the aim to contribute to existing dynamic global vegetation models. It provides high-quality data and real-time simulations in order to advance research on the impact of climate change on the biological response of trees and forests. Besides its application in natural forests to answer climate-change related scientific and political questions, we also envision a broader societal application of TreeWatch.net by selecting trees in nature reserves, public areas, cities, university areas, schoolyards, and parks to teach youngsters and create public awareness on the effects of changing weather conditions on trees and forests in this era of climate change.

Parameterized models of biophysical and mechanical cell properties are important for predictive mathematical modeling of cellular processes. The concepts of turgor, cell wall elasticity, osmotically active volume, and intracellular osmolarity have been investigated for decades, but a consistent rigorous parameterization of these concepts is lacking. Here, we subjected several data sets of minimum volume measurements in yeast obtained after hyper-osmotic shock to a thermodynamic modeling framework. We estimated parameters for several relevant biophysical cell properties and tested alternative hypotheses about these concepts using a model discrimination approach. In accordance with previous reports, we estimated an average initial turgor of 0.6 ± 0.2 MPa and found that turgor becomes negligible at a relative volume of 93.3 ± 6.3% corresponding to an osmotic shock of 0.4 ± 0.2 Osm/l. At high stress levels (4 Osm/l), plasmolysis may occur. We found that the volumetric elastic modulus, a measure of cell wall elasticity, is 14.3 ± 10.4 MPa. Our model discrimination analysis suggests that other thermodynamic quantities affecting the intracellular water potential, for example the matrix potential, can be neglected under physiological conditions. The parameterized turgor models showed that activation of the osmosensing high osmolarity glycerol (HOG) signaling pathway correlates with turgor loss in a 1:1 relationship. This finding suggests that mechanical properties of the membrane trigger HOG pathway activation, which can be represented and quantitatively modeled by turgor. This work was supported via several projects funded by the European Commission: QUASI (Contract No. 503230 to SH, EK, FP and MP), CELLCOMPUT (Contract No. 043310 to SH, EK and FP), UNICELLSYS (Contract No. 201142 to SH, EK, FP, MP and MG), SYSTEMSBIOLOGY (Contract No. 514169 to SH and EK), and AMPKIN (Contract No. 518181 to SH and MG). In addition work was funded by grants from the Swedish Foundation for Strategic Research SSF (Bio-X to MG), the Swedish Research Council (project grants to SH and MG), the Carl Trygger Foundation (to MG), the Science Faculty, University of Gothenburg (to SH and MG), and the Swiss systemsX.ch (to MP)

The Candida albicans RHR2 gene, which specifies a glycerol biosynthetic enzyme, is required for biofilm formation in vitro and in vivo. Prior studies indicate that RHR2 is ultimately required for expression of adhesin genes, such as ALS1. In fact, RHR2 is unnecessary for biofilm formation when ALS1 is overexpressed from an RHR2-independent promoter. Here, we describe two additional biological processes that depend upon RHR2: invasion into an abiotic substrate and pathogenicity in an abdominal infection model. We report here that abiotic substrate invasion occurs concomitantly with biofilm formation, and a screen of transcription factor mutants indicates that biofilm and hyphal formation ability correlates with invasion ability. However, analysis presented here of the rhr2Δ/Δ mutant separates biofilm formation and invasion. We found that an rhr2Δ/Δ mutant forms a biofilm upon overexpression of the adhesin gene ALS1 or the transcription factor genes BRG1 or UME6. However, the biofilm-forming strains do not invade the substrate. These results indicate that RHR2 has an adhesin-independent role in substrate invasion, and mathematical modeling argues that RHR2 is required to generate turgor. Previous studies have shown that abdominal infection by C. albicans has two aspects: infection of abdominal organs and persistence in abscesses. We report here that an rhr2Δ/Δ mutant is defective in both of these infection phenotypes. We find here that overexpression of ALS1 in the mutant restores infection of organs, but does not improve persistence in abscesses. Therefore, RHR2 has an adhesin-independent role in abdominal infection, just as it does in substrate invasion. This report suggests that RHR2, through glycerol synthesis, coordinates adherence with host- or substrate-interaction activities that enable proliferation of the C. albicans population.

Antiquitin is an evolutionarily conserved protein believed to play a role in the regulation of cellular turgor. Based on sequence analysis, this protein is classified as a member of the aldehyde dehydrogenase superfamily. All previous studies on antiquitin have been confined to the nucleotide level, and the protein has never been purified and characterized. In the present investigation, the antiquitin protein was purified for the first time. An acetaldehyde-oxidizing protein was isolated from the liver of black seabream (Mylio macrocephalus) by chromatographies on α-cyanocinnamate Sepharose and Affi-gel Blue agarose, followed by ammonium sulfate precipitation. The purified protein was identified as antiquitin by the first 18 N-terminal amino acid residues which showed 83.3% identity with the deduced sequence of human antiquitin. Electrophoretic mobility studies indicated that black seabream antiquitin is a tetramer with a subunit molecular mass of 57.5 kDa. Kinetic analysis of the purified protein indicated that it catalyzes the oxidation of acetaldehyde with Km and Vmax values of 2.0 mM and 1.3 U/mg, respectively. The longer aliphatic propionaldehyde and the aromatic benzaldehyde are also substrates of the purified enzyme. The enzyme is highly specific towards NAD+ as the coenzyme and is totally inactive towards NADP+. Maximal enzymatic activity was found at about pH 9–10.

A two-dimensional multiscale water transport and mechanical model was developed to predict the water loss and deformation of apple tissue (Malus × domestica Borkh. cv. 'Jonagold') during dehydration. At the macroscopic level, a continuum approach was used to construct a coupled water transport and mechanical model. Water transport in the tissue was simulated using a phenomenological approach using Fick's second law of diffusion. Mechanical deformation due to shrinkage was based on a structural mechanics model consisting of two parts: Yeoh strain energy functions to account for non-linearity and Maxwell's rheological model of visco-elasticity. Apparent parameters of the macroscale model were computed from a microscale model. The latter accounted for water exchange between different microscopic structures of the tissue (intercellular space, the cell wall network and cytoplasm) using transport laws with the water potential as the driving force for water exchange between different compartments of tissue. The microscale deformation mechanics were computed using a model where the cells were represented as a closed thin walled structure. The predicted apparent water transport properties of apple cortex tissue from the microscale model showed good agreement with the experimentally measured values. Deviations between calculated and measured mechanical properties of apple tissue were observed at strains larger than 3%, and were attributed to differences in water transport behavior between the experimental compression tests and the simulated dehydration-deformation behavior. Tissue dehydration and deformation in the high relative humidity range ( > 97% RH) could, however, be accurately predicted by the multiscale model. The multiscale model helped to understand the dynamics of the dehydration process and the importance of the different microstructural compartments (intercellular space, cell wall, membrane and cytoplasm) for water transport and mechanical deformation. ispartof: Journal of Physics - Condensed Matter vol:26 issue:46 ispartof: location:England status: published

In order to investigate the responses of leaf elongation rate (LER), turgor and osmotic adjustment (OA) during a short-term stress (7 hours) imposed by PEG6000 and a recovery phase, three durum wheat (Triticum durum L.) varieties [Inrat; MBB; and OZ ] were grown in aerated nutrient solutions. Leaf elongation kinetics of leaf 3 was estimated using LVDT. Turgor was estimated using a cell pressure probe; osmotic potential as well as total sugars and potassium (K+) concentrations were estimated from expressed sap of elongation zone. Growth recovered rapidly and then stabilised at a lower value. A significant difference was found in % recovery of LER between the varieties. The cessation of growth after stress coincided with a decrease in turgor followed by a recovery period reaching control values in MBB and Inrat. A strong correlation (R2 = 0.83) between the reduction in turgor (Δ turgor) and % recovery of LER was found at 7 hours after stress. The difference in the partial recovery of LER between varieties was thus related to the capacity of partial turgor recovery. Partial turgor recovery is associated with sugar or K+ based OA which indicates its importance in maintaining high LER values under water deficit.

International audience; In plants, the vacuole is a multifunctional organelle with an important role in the maintenance of the intracellular space. Tonoplast membranes are highly permeable to water due to their content in aquaporins TIPs (Tonoplast Intrinsic Proteins) that allow the rapid water influx creating an internal turgor pressure responsible for cell expansion, elongation and shape. The aim of the present study was to evaluate if the grapevine Vitis vinifera TIP2;1 would operate as a possible volume regulator gated by membrane surface tension. For that, the wild type VvTIP2;1 and a non-functional mutated form were heterologous expressed in yeast. Using an experimental strategy in which cells are incubated in external media that induce an increase in internal hydrostatic pressure and consequently membrane surface tension, we were able to compare the osmotic permeability (P-f) and the activation energy for water transport (E-a) of yeast strains expressing the functional and a non-functional TIP2;1. We found P-f and E-a dependence on internal turgor pressure only for the strain harboring the functional aquaporin indicating that TIP2;1 activity is regulated by membrane tension changing from an open to a closed state in an internal pressure dependent manner. This turgor dependent gating of TIP2;1 might be a mechanism to regulate vacuolar size and shape in plants withstanding hostile drought conditions such as grapevine.

International audience; Fruits contain polyphenols, widespread antioxidants beneficial for human health. Their mass transfer was studied during the leaching of apple slices immersed in mannitol solutions with ranging concentrations (0, 0.2, 0.4, and 0.6 M). The solution of Fick’s law for unsteady mass transfer in planar configuration was used to calculate apparent diffusivity (De). Polyphenols were quantified by high-performance liquid chromatography for each immersion time. Leaching from raw apple tissues occurred only when cell integrity was lost, here at a certain level of difference in osmotic pressure. Different diffusivity values were found in the two apple varieties. Values of De either decreased from 0.2 to 0.1 × 10−9 and 0.2 × 10−9 m2 s−1 for Golden Delicious and Granny Smith, respectively, or were not determined when the mannitol concentration increased from 0 to 0.6 M. The osmotic strength of the solution strongly impacted the leaching rate of polyphenols from apple cells. The structure of the polyphenols also affected De, with low values for procyanidins.

In order to elucidate stomatal response to wind, leaf gas exchange and stomatal conductance in an intact leaf of cucumber plants (Cucumis sativus L.) were measured under different conditions of air current and humidity. A leaf gas exchange cuvette was improved for individual measurements on the abaxial and adaxial leaf surfaces and for adjustment of the leaf boundary air current, where leaf boundary layer conductance can be adjusted at a desired value within a range from 0.3mol m^s^ to 1.0mol m^s^. Rates of leaf gas exchange and stomatal conductance were higher on the abaxial surface than on the adaxial surface. Stomatal response to wind was appeared more sensitive on the abaxial surface, while leaf gas exchange and stomatal conductance on the adaxial surface was scarcely affected by wind. Under the humid air condition, increase in leaf boundary layer conductance significantly enhanced stomatal conductance as well as rates of transpiration and photosynthesis on the abaxial surface. On the other hand, under the dry air condition, stomatal conductance was depressed by increase in leaf boundary layer conductance with little effect on transpiration and photosynthesis. These opposite changes in stomatal conductance found under the humid and dry air conditions were proved visually as change in stomatal aperture by the microscopic observation of the abaxial leaf surface. This stomatal response to wind found on the abaxial surface was not related to feedback stomatal response to transpirational water loss and intercellular CO_2 concentration in the leaf. The mechanism of stomatal response to wind was explained on the basis of water balance within the stomatal complex and on the antagonism relationship between turgors in guard and epidermal cells.

Raízes de cenoura Daucus Carota L. Brasília recém-colhidas foram submetidas a diferentes níveis de desidratação com emprego de ventilação forçada a 25 ± 2 °C. Sob teores relativos de água inferiores a 0,95 a firmeza dependente da pressão celular, medida com a técnica da aplanação, ficou reduzida a praticamente zero, ao passo que as raízes do tratamento controle tiveram firmeza acima de 7,0 kgf cm-2. Após o armazenamento em sacos plásticos de polietileno de baixa densidade, durante 67dias a 5 ± 2 °C, as raízes que tiveram seu teor relativo de água reduzido a menos de 0,75 recuperaram a firmeza em mais de 60% da turgescência inicial do controle, além de apresentarem brotação. A recuperação da firmeza ocorreu sem absorção de água, visto que o armazenamento em embalagens de plástico diminuiu mas não anulou a transpiração. Essa recuperação da firmeza e a posterior brotação contrariou a expectativa inicial de que as raízes murchas não brotariam. Duas hipóteses foram postuladas para explicar esses resultados: a primeira seria o envolvimento de um processo de redistribuição de água na raiz; a segunda, a redução do volume do órgão, de acordo com a teoria coesiva do encolhimento celular. A favor da primeira hipótese pesou a formação de pequenas lacunas lisógenas distribuídas a partir do centro do cilindro vascular. O volume total dessas cavidades lisógenas corresponderia a uma quantidade de água aparentemente inferior a 2% do volume da raiz, a qual seria insuficiente para explicar a recuperação da firmeza em raízes que perderam mais de 20% de seu conteúdo de água. Fica a possibilidade de haverem outras causas não percebidas de redistribuição de água ou que, de fato, a presumida redução plástica do volume das células - de acordo com a teoria coesiva do encolhimento celular - tenha ocorrido.'Brasília' carrot roots (Daucus carota L.) have been exposed to different dehydration levels through the use of forced ventilation at 25 ± 2 °C. At relative water content smaller than 0.95, the turgor-dependent firmness, measured by the external force method, has been reduced to nearly zero, control roots had a firmness above 7.0 kgf cm-2. After a 67 day storage at 5 ± 2 °C, roots that had their initial relative water contents reduced to less than 0.75, presented a firmness recovery to more than 60%, as compared with that of the control roots, in addition showing significant sprouting. These levels of firmness recovery and sprouting had not been previously described. Two hypothesis have been put forward to explain those results: a) occurrence of water relocation process in the roots; b) the theory of cellular cohesive shrinkage. The formation of small lisogenous cavities would favor the first hypothesis; however, accounting for less than 2% of the root volume, they would not be enough to explain the firmness recovery observed in roots with water volume reduction above 20%. By exclusion, it seems that cellular cohesive shrinkage has been the main factor in the firmness recovery observed, allowing significant sprouting in dry roots.