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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. [ABSTRACT FROM AUTHOR]

Increases in drought frequency and insect defoliation are emerging threats that typically affect the plantation production of Populus yunnanensis, which is an endemic dioecious tree species in China. Nevertheless, it is difficult to predict which sex of P. yunnanensis will be more affected by the combined effects of water limitations and defoliation. In this study, we examined the combined effects of progressive drought and defoliation on water relations, growth, gas exchange and leaf carbohydrate reserves in P. yunnanensis females and males to test whether defoliation alters the effects of drought and and how this response varies between genders. The experimental design included two watering regimes (well-watered and drought-stressed) and two levels of defoliation (leaves untouched and 60% defoliated). Defoliation exacerbated drought stress in females by decreasing photosynthesis, dry mass accumulation and leaf non-structural carbohydrate (NSC) concentration. In contrast, the total biomass of males grown under drought combined with defoliation was not significantly altered when compared to those grown under drought alone. These results suggest that defoliation does not aggravate the drought effects on males. The males presented a high capacity to maintain foliar water status through stomatal control under drought conditions irrespective of defoliation treatment. The conservative water use strategy in males resulted in a gradual reduction in leaf water potential, gas exchange rates and NSC. Our data showed that the different responses of the females and males to drought and defoliation were influenced by plant water status and consequent effects on changes in carbon assimilation and leaf non-structural carbohydrate reserves. [ABSTRACT FROM AUTHOR]

Background: water shortage is one of the major factor effects on growth characters and yield of most crops. Objective: this study was conducted to get to know the reactions of some Egyptian cotton genotypes to water deficit. Methods: The genetic materials used in this study included thirteen cotton genotypes belonging to Gossypium barbadense L., from the Cotton Research Institute (CRI), which was devoted to establishing the experimental materials for this investigation. Results: the ratio of GCA/SCA was less than unity for all studied indices, indicating predominance of non-additive gene action (dominance and epistasis), which is an important in exploitation of heterosis through hybrid breeding. Results: The data showed significant reduction in water relationship characters for all parental genotypes under stress conditions. The Egyptian variety Giza 68 gave high values for most water relationship characters. Data revealed that the greater the value of tolerance index is, the larger the yield reduction is under water deficit conditions and the higher the stress sensitivity is becoming. The parental genotypes Giza 96 showed the highest reduction in yield under water deficit conditions. At the same time, the cross combination Minufy x Australy showed higher values of yield reduction followed by the combinations Giza 67 x Australy. Of the male parents, the Russian genotype 10229 recorded the best GCA values for most water relationship characters. At the same time, the female parents, the old Egyptian genotype Giza 67 recorded the best values and exhibited good general combined for most water relationship characters. The cross combinations Giza 86 x Pima S6, Giza 77 x Pima S6, Giza 94 x Dandra and Giza 96 x Australy showed significant desirable SCA effect for most characters. Conclusion: relative water content %, osmotic pressure, chlorophyll and carotenoids content indicates better availability of water in the cell, which increases the photosynthetic rate. Also, the higher level of proline accumulation in the leaves which was recorded under deficit water suggests that the production of proline is probably a common response of plant under water deficit conditions. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the growth and physiological responses cotton plants to salt stress. At seven leaf stage, cotton plants were subjected to two treatments; 0 mM NaCl as the control and 150 mM NaCl as the salt stress treatment, respectively. The effect of salt stress on leaf gas exchange rates, leaf nitrogen concentration, chlorophyll content, leaf K+ and Na+ concentrations, plant water status, endogenous phytohormone concentrations, dry matter accumulation and partitioning in plant organs was evaluated. The results showed that salt stress significantly decreased plant growth, water consumption, leaf water relations characteristics and leaf gas exchange rates as compared to the control. Under salt, photosynthetic rate was reduced to less extend than did stomatal conductance (gs) and transpiration rate, resulting in greater intrinsic and instantaneous water use efficiencies compared to the control plants. gs decreased linearly with decreasing leaf water potential and leaf hydraulic conductance under salt. Salt‐stressed plants possessed a significant higher concentration of abscisic acid ([ABA]leaf), while a significantly lower concentrations of gibberellic acid ([GA3]leaf) and zeatin riboside ([ZR]leaf) in leaf than those grown under control. Negative linear relationships were found between gs and [ABA]leaf, ratio of [ABA]leaf to [GA3]leaf, ratio of [ABA]leaf to ([GA3]leaf+[ZR]leaf), respectively. Salt stress significantly decreased leaf K+ concentration, the ratio of K+/Na+ in leaf, shoot growth and biomass partitioning into leaf and stem, whereas increased leaf chlorophyll content, leaf nitrogen concentration and biomass partitioning into boll. Although the water use efficiency of plant biomass was unaffected, the water use efficiency of boll biomass was significantly enhanced by salt stress. Collectively, salt‐induced changes in both hydraulic and chemical properties were involved in mediating the leaf gas exchange response to salt stress, and the enhanced leaf nitrogen concentration and biomass partitioning into boll may lead to a sustained yield with less water consumption in cotton plants grown under moderate salinity stress. [ABSTRACT FROM AUTHOR]

Abstract The study of transpiration, water, and nutrient uptake during abiotic stress in the root zone is hindered because of the hidden nature of the root zone. In this study, a modified aeroponic system was used to evaluate whole plant transpiration, nitrate and water uptake in the growth and development of tomato plants in response to salinity. Tomato seedlings were exposed to three levels of salinity (1.5, 4.5, and 9 dSm−1) and three levels of nitrate (1, 4, and 8 mM NO3) in a separate experiments conducted concurrently. Whole plant transpiration, water and nitrate uptake were estimated. Our study revealed that ~30 to 35 days after treatment (DAT), water uptake rate per plant increased from a common initial rate of about 0.05 to 1.1, 0.6, and 0.4 kg/day at 1.5, 4.5, and 9 dSm−1 respectively. The NO3 uptake rates in tomatoes grown in 1 and 4 mM NO3 were 5.5 and 22% respectively, of the uptake of tomatoes grown in 8 mM NO3. The estimation of nitrate uptake and lower sensitivity to salinity stress in the aeroponic showed the effectiveness and cost efficiency of the system in the cultivation of vegetables during abiotic stresses. The novelty of the system described is the continuous estimation of root and nutrient uptake by the whole plant at any given time.

The energetic state of water in the soil-plant system is a relevant theme in ecosystems affected by abiotic stress. Thus, the present study aimed to investigate the water potential in soil and in sorghum grown in Fluvisol irrigated with water of increasing electrical conductivity and different ionic compositions. Solutions were prepared with different ionic compositions (NaCl and a salt mix) and with six increasing levels of electrical conductivity (0, 2.5, 5.0, 7.5, 10, and 12.5 dS m−1), with a randomized block design and 4 repetitions. The leaf water potential and leaf osmotic potential were determined 60 days after sowing. The soil osmotic potential was measured by saturation paste and the matric potential was estimated by the soil water retention curve. The increase in electrical conductivity, regardless of the type of saline solution applied, causes interference in the energy status of the water in the soil, especially concerning the osmotic potential. The type of salt exerts an influence on the water potential in the soil. In contrast, the salt type does not influence the potentials of water in the plant. It is not recommended adopting the same values of water total potential for the soil determined in sorghum at night. [ABSTRACT FROM AUTHOR]

With continued climate changes, soil drought stress has become the main limiting factor for crop growth in arid and semi‐arid regions. A typical characteristic of drought stress is the burst of reactive oxygen species (ROS), causing oxidative damage. Plant‐associated microbes, such as arbuscular mycorrhizal fungi (AMF), can regulate physiological and molecular responses to tolerate drought stress, and they have a strong ability to cope with drought‐induced oxidative damage via enhanced antioxidant defence systems. AMF produce a limited oxidative burst in the arbuscule‐containing root cortical cells. Similar to plants, AMF modulate a fungal network in enzymatic (e.g. GmarCuZnSOD and GintSOD1) and non‐enzymatic (e.g. GintMT1, GinPDX1 and GintGRX1) antioxidant defence systems to scavenge ROS. Plants also respond to mycorrhization to enhance stress tolerance via metabolites and the induction of genes. The present review provides an overview of the network of plant − arbuscular mycorrhizal fungus dialogue in mitigating oxidative stress. Future studies should involve identifying genes and transcription factors from both AMF and host plants in response to drought stress, and utilize transcriptomics, proteomics and metabolomics to clarify a clear dialogue mechanism between plants and AMF in mitigating oxidative burst. [ABSTRACT FROM AUTHOR]

Premise: The distribution and even the survival of plant species are influenced by temperature. In an old climatically buffered infertile landscape (OCBIL) in Brazil, we previously characterized different strategies for foliar water uptake (FWU). It is possible that photosystem II tolerance to heat and excessive light intensity varies among species with different FWU capacities. Methods: The relationship between FWU, photoinhibition, and thermotolerance was investigated in seven species from this ecosystem. Results: The species with slow water absorption and high water absorption are those that presented less photoinhibition. Contrastingly, the species that have fast and low water absorption presented greater thermotolerance when their leaves are totally hydrated. However, when there is greater leaf dehydration, the most thermotolerant species were those with slow but high water absorption. Conclusions: Foliar water uptake is an important trait for plants to tolerate excessive light intensity and higher temperatures. Plants in this OCBIL may be differentially affected by future global warming, and the best strategy to deal with this expected climate change is with slow and high absorption of water. [ABSTRACT FROM AUTHOR]

Catchment-scale recharge and water balance estimates are commonly made for the purposes of water resource management. Few catchments have had these estimates ground-truthed. One confounding aspect is that runoff and soil-water inputs commonly occur throughout the year; however, in climates with strong dry seasons, base flow can be directly sampled. In an experimental catchment in the Mt. Lofty Ranges of South Australia, run-of-stream hydrochemical parameters were monitored. In this Mediterranean climate during the Millennium Drought (2001–2009), the stream was reduced to disconnected groundwater-fed pools. Two groundwater types were identified: (1) high-salinity type from meta-shale bedrock with thick, clayey regolith and (2) low-salinity type from meta-sandstone bedrock with sandy regolith. End-member mixing using silica and chloride concentrations and robust 87Sr/86Sr ratios reveal an apparent groundwater-flow paradox as follows. According to chloride mass balance and spatial distribution of hydrogeological units, the low-salinity groundwater type has seven times more recharge than the high-salinity type. Over the 28-year record, low-salinity groundwater contributed 25% of stream water, whereas high-salinity groundwater contributed 2–5%. During the drought year, however, annual stream flow from the high-salinity groundwater contributed 50%, whereas low-salinity groundwater contributed 18%. High-salinity groundwater dominated dry-season base flow during all years. The paradox can be resolved as follows: The meta-sandstone terrane drains quickly following wet-season recharge and therefore contributes little to dry-season base flow. Conversely, the meta-shale terrane drains slowly and therefore provides stream flow during dry seasons and drought years. [ABSTRACT FROM AUTHOR]

Drought stress has a negative impact on crop growth and productivity worldwide. Plant symbionts such as arbuscular mycorrhizal fungi (AMF) can enhance plant growth and improve plant resistance to drought stress. AMF mixture inocula and plant responses to drought still require further study. The objective of this study was to investigate the effects of non-inoculation (NM) or inoculation with three commercial AMF inocula containing a single or mixtures comprising different numbers of AMF species: M1 (Rhizophagus intraradices), M2 (Rhizophagus clarus, R. intraradices, Septoglomus deserticola, Funneliformis mosseae), and M3 (Rhizophagus intraradices, R. aggregatum, Funneliformis mosseae, Olaroideoglomus etunicatum) on growth, nutritional, and physiological responses of soybean (Glycine max L. cv. Hutcheson) grown in a greenhouse under different water stress levels [WW = well watered (90% FC), MS = medium (60% FC) and SS = severe stressed (30% FC)]. The AMF-inoculated plants had significantly higher plant biomass, chlorophyll content, stomatal conductance, leaf water relations, and mineral contents in comparison to NM plants. Applied mycorrhizal inocula differed in their response to water-deficit conditions. M2 inoculant generally supported greater plant biomass, stomatal conductance, leaf water content, and leaf N, P, K, S, Mn, and Cu contents than M1 and M3 inocula, especially under MS and SS treatments. These results indicated that all mycorrhizal inocula supported plant growth both generally and with soil water deficit; however, M2-inoculated plants performed better than M1 and M3 under drought stress. Therefore, mycorrhizal inocula are effective for supporting soybean growth and offsetting the effects of drought and AMF technology that can support sustainable crop cultivation under soil water-deficit conditions. Different types of inocula have different effects, however, and thus require testing for individual crops. [ABSTRACT FROM AUTHOR]

The study of transpiration, water, and nutrient uptake during abiotic stress in the root zone is hindered because of the hidden nature of the root zone. In this study, a modified aeroponic system was used to evaluate whole plant transpiration, nitrate and water uptake in the growth and development of tomato plants in response to salinity. Tomato seedlings were exposed to three levels of salinity (1.5, 4.5, and 9 dSm-1) and three levels of nitrate (1, 4, and 8 mM NO3) in a separate experiments conducted concurrently. Whole plant transpiration, water and nitrate uptake were estimated. Our study revealed that ~30 to 35 days after treatment (DAT), water uptake rate per plant increased from a common initial rate of about 0.05 to 1.1, 0.6, and 0.4 kg/day at 1.5, 4.5, and 9 dSm-1 respectively. The NO3 uptake rates in tomatoes grown in 1 and 4 mM NO3 were 5.5 and 22% respectively, of the uptake of tomatoes grown in 8 mM NO3. The estimation of nitrate uptake and lower sensitivity to salinity stress in the aeroponic showed the effectiveness and cost efficiency of the system in the cultivation of vegetables during abiotic stresses. The novelty of the system described is the continuous estimation of root and nutrient uptake by the whole plant at any given time. [ABSTRACT FROM AUTHOR]

Root pressure, also manifested as profusive sap flowing from cut stems, is a phenomenon in some species that has perplexed biologists for much of the last century. It is associated with increased crop production under drought, but its function and regulation remain largely unknown. In this study, we investigated the initiation, mechanisms, and possible adaptive function of root pressure in six genotypes of Sorghum bicolor during a drought experiment in the greenhouse. We observed that root pressure was induced in plants exposed to drought followed by re-watering but possibly inhibited by 100% re-watering in some genotypes. We found that root pressure in drought stressed and re-watered plants was associated with greater ratio of fine: coarse root length and shoot biomass production, indicating a possible role of root allocation in creating root pressure and adaptive benefit of root pressure for shoot biomass production. Using RNA-Seq, we identified gene transcripts that were up- and down-regulated in plants with root pressure expression, focusing on genes for aquaporins, membrane transporters, and ATPases that could regulate inter- and intra-cellular transport of water and ions to generate positive xylem pressure in root tissue.

Pistachio nuts are an economically important commodity produced by many countries. They can be colonized by mycotoxigenic fungi, especially Aspergillus flavus, resulting in contamination with aflatoxins (AFs), especially aflatoxin B1 (AFB1), a Class 1a carcinogen. The objectives were to examine the effect of interactions between the two key abiotic factors, temperature and water activity (aw) on (a) in vitro growth and AFB1 production by four strains of A. flavus isolated from pistachio nuts, on a milled pistachio nut medium modified ionically (NaCl) and non-ionically (glycerol) in the range 20–35°C and 0.995–0.85 aw, (b) colonization of layers of raw pistachio nuts stored at different interacting temperature x aw conditions and on relative AFB1 production and (c) develop models to produce contour maps of the optimal and marginal boundary conditions for growth and AFB1 production by up to 4 strains of this species. On pistachio nut-based media, optimum growth of four strains of A. flavus was at 0.98–0.95 aw and 30–35°C. Optimum AFB1 production was at 30–35°C and 0.98 aw. No significant differences in growth was found on ionic and non-ionically modified media. Colonization of layers of raw pistachio nuts was slower and contamination with AFB1 significantly less than in in vitro studies. Contour maps based on the pooled data for up to four strains (in vitro, in situ) showed the optimum and marginal conditions for growth and AFB1 production. These data can be used to identify those conditions which represent a high, intermediate or low risk of colonization and AFB1 contamination in the pistachio nut processing chain. These results are discussed in the context of the development of appropriate intervention strategies to minimize AFB1 contamination of this economically important commodity.

Mature oak stands of different tree height at four sandy valley river sites (Quercus robur) and one south-exposed schist slope (Qu. petraea) in the middle Rhine and lower Main valley were studied from early summer 2017 (normal wet year) until the end of 2018 (extremely hot and dry year). Tree water relations (ΨPD, RWC, sap flow rates) were monitored together with soil water relations, LAI and leaf chl content. In two sandy sites with presumed continuous capillary water access from the groundwater aquifer, sap flow rates of the large trees (30 m) and estimated canopy conductance decreased to about 50% of the maximum value in the course of summer 2018, but recovered in autumn. At two other sites, with smaller trees (14–24 m) and presumed interrupted capillary water access during mid-summer 2018, sap flow rates and canopy conductance broke down completely and trees shed a large proportion of leaves in summer. In one of these sites, ΨPD decreased (reversibly) to -4 MPa, one of the lowest values reported in the literature for central Europe, and tree damage resulted not only in extreme leaf shedding, but also in susceptibility to uprooting (in 2 out of 5 measured trees) by thunderstorm gusts in autumn 2018. At the schist slope site, where oaks reached the lowest height and stand density of all sites, sap flow rates remained similar to the values found at the presumed capillary-water supplied sandy sites, indicating access to rock fissure water even at the peak of the drought period. Our findings corroborate the prediction from vegetation modelling that several Qu. robur stands in the Rhine-Main valleys will be prone to severe forest dieback in the forthcoming decades.

To set-up afforestation and reforestation projects in arid regions southern Tunisia, several indigenous and exotic forest species were used among them are Acacia spp. However, the success of these projects remains highly sceptical because of the intensified aridity during the last decade. To overcome this issue, the selection of genotypes resistant to severe drought is crucial as first step. For this reason, the aim of the present study is to compare tolerance capacity to severe drought between two Acacia species (A. cyclops and A. salicina) and evaluate efficacy of their biochemical responses at leaf and root levels. Combined physiological and biochemical approaches were adopted. Two-years-old plants of two Acacia species (A. cyclops and A. salicina), frequently used in forestation projects in arid regions southern Tunisia, were subjected to severe water stress by withholding watering during 60 days. At regular intervals, water relations and net photosynthetic rate (Pn) were measured. In addition, the biochemical response was characterized by quantifying one sugar alcohol (arabitol) and three cyclitols (myo-inositol, pinitol and quercitol) in leaves and roots. Our results revealed that A. cyclops was more tolerant to severe drought than A. salicina. The turgor of its leaf tissues and its Pn were less affected. The superiority of A. cyclops to tolerate severe water stress might be attributed to greater efficiency of its biochemical defense mechanisms compared to A. salicina. Comparison of biochemical profiles between species exhibited some differences depending on the organs and the species. For development and survival under severe drought conditions, A. cyclops accomplished efficient osmoregualation and osmoprotection mechanisms by massive accumulation of specific polyols distinctly in leaves and roots. Indeed, compared to A. salicina, A. cyclops accumulated higher amount of arabitol, myo-inositol and quercitol in roots, but pinitol in leaves. So, contents of these polyols might be used as promising criteria for the selection of drought-tolerant Acacia species.

Carnation (Dianthus caryophyllus L.) and chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitam.] cut flowers are among the most important commodities that dominate flower markets throughout the world. Two major problems in the transportation and marketing of these flowers are their relatively short vase life and the rapid decline of their aesthetic value. In this respect, the current study investigates the effects of silver nanoparticles (AgNPs) on ethylene-sensitive (carnation) and ethylene-insensitive (chrysanthemum) cut flowers. Specifically, this research examines their morpho-physicochemical characteristics, antioxidant enzyme activities and vase life. Here, the AgNPs were synthesized by chemical methods and then applied on both flowers by a pulsing method. The treatments involved two concentrations of AgNPs (0.04 and 0.08gL-1) along with the control (deionized water), and the duration of exposure lasted for 24 h. Then, the flower stems were placed in an aqueous sucrose solution (4%) until the end of the experiment. All traits, except the vase life, were evaluated after 0, 3, 6 and 9 d following the treatments during the vase period. During this time, the control groups of both flowers showed considerable amounts of decrease in the relative fresh weight (RFW), vase solution uptake (VSU), flower diameter, membrane stability index (MSI) and total soluble carbohydrate (TSC). Meanwhile, there were increases in hydrogen peroxide content (H2O2) and peroxidase (POD) activity. The bacterial population of the stem end and total soluble protein (TSP) increased in carnation petals, but decreased in chrysanthemum petals. The activity of superoxide dismutase (SOD) dropped in carnation petals, whereas it rose in chrysanthemum petals. Using AgNPs at concentrations of 0.08 and 0.04gL-1 can optimally extend the vase life of carnation and chrysanthemum, respectively.

Flower senescence varies among cut roses (Rosa hybrida L.), and it is known that the postharvest life of ethylene-sensitive flowers is strongly related to the transcriptional accumulation of ethylene biosynthesis genes, whereas that of ethylene-insensitive flowers is shortened by water stress. These different responses of flowers to hormone and water stresses limit the action of preservatives in inhibiting the postharvest deterioration of cut rose flowers. This study was conducted to investigate the effects of the combined application of antibacterial agents and ethylene biosynthesis and binding inhibitors on the postharvest life and quality of the cut rose cultivars ‘Matador’ (ethylene-sensitive) and ‘Dolcetto’ (ethylene-insensitive). Cut flowers were treated with nano silver (NS), a combination of NS and α-aminoisobutyric acid (NS+A), or a combination of NS+A and 1-methylcyclopropene (NS+AM), and they were subsequently exposed to ethylene for 24 h. Treatment effectiveness was compared with that of control (CON) flowers, which were kept in distilled water and exposed only to ethylene. The results showed that all treatments significantly improved the postharvest quality and vase life of both rose cultivars. However, NS+AM most markedly delayed senescence and prolonged the vase life of cut flowers by 217% in ‘Matador’ and 168.4% in ‘Dolcetto’, compared with those of CON flowers. NS+AM also effectively increased the flower diameter and maintenance time of positive water balance and initial fresh weight by enhancing solution absorption as well as suppressing bacterial growth at the cut stem ends of the cut roses. Furthermore, NS+AM greatly suppressed the ethylene-inducible increase of ethylene biosynthesis genes and the reduction of ethylene receptor genes in petals, which resulted in a reduced flower response to exogenous ethylene in both rose cultivars. These findings show that NS+AM effectively delays flower senescence in both ethylene sensitive and insensitive cultivars by synergistically preventing ethylene response and water stress in cut flowers.

Traditional mulch material (farmyard manure) has long been used in agriculture. However, recent developments have also introduced the scientific community and farmers to advanced chemicals such as potassium polyacrylamide (KPAM), which has revolutionised the concept of the soil water-holding capacity to many compared with other materials being used. To compare the effect of different organic and inorganic soil amendment materials under water stress conditions, a two-year (2018 and 2019) field study was conducted. The main plots consisted of irrigation treatments, i.e., I0 (control irrigation), I1 (drought-induced by skipping irrigation at the 4th leaf stage), and I2 (drought-induced by skipping irrigation at the anthesis stage). The subplots included a control treatment and soil amended with different conditioners such as potassium polyacrylamide (KPAM, 30 kg/ha), farmyard manure (FYM, 4 tons/ha), and biochar (10 tons/ha); these were mixed thoroughly with the soil before sowing. The results showed a significant reduction in the water relation parameters (water potential up to 35.77% and relative water content up to 21%), gas exchange parameters (net CO2 assimilation rate up to 28.85%, stomatal conductance up to 43.18%, and transpiration rate up to 49.07%), and yield attributes (biological yield up to 8.45% and grain yield up to 32.22%) under drought stress conditions. In addition, water stress also induced an increase in the synthesis of osmoprotectants (proline up to 77.74%, total soluble sugars up to 27.43%, and total free amino acids up to 11.73%). Among all the soil conditioners used, KPAM significantly reduced the negative effects of drought stress on the wheat plants. Thus, it could be concluded that the use of soil conditioners is a promising method for dealing with the negative consequences of drought stress for achieving sustainable crop yields.

Abstract. Aim. Study the ecophysiological reaction of Nerium oleander L. on effect of progressive soil drought. Estimate the optimal and threshold values of environmental factors limiting photosynthesis rate of Nerium oleander L. plants. Materials and Methods. As the research materials, were used the young plants of Nerium oleander L. For continuous automatic recording of CO2/H2O gas exchange of intact leaves we used PTM-48A Photosynthesis Monitor. Results. It was established that N.oleander begins sense a water stress deficit during the critical period of active growth by reducing soil moisture content up to 35% field capacity (FC). Net photosynthesis (PN) and stomata conductance (gs) decreased under progressive soil drought stress and dropped to zero under condition: soil water beneath 2-4%VWC (6-11% FC) during more than 24 hours, leaves temperature – more than 37°C and PAR – more than 1300-1700 µmol/(m2 s). Optimal light and temperature conditions for intensive growth: leaf temperature from 23 to 36.5°C, light regime: full sunlight in the range PAR 850-1600 µmol/(m2 s) when soil moisture 45-75% FC. Conclusion. Genotypic characteristics of N. oleander plants in supporting optimal on accordance with the environmental conditions water balance were determined. One of the specific adaptation reaction for N. oleander to extreme drought conditions in case of complex influence of water stress (soil water content at level of wilting range (

Root pressure, also manifested as profusive sap flowing from cut stems, is a phenomenon in some species that has perplexed biologists for much of the last century. It is associated with increased crop production under drought, but its function and regulation remain largely unknown. In this study, we investigated the initiation, mechanisms, and possible adaptive function of root pressure in six genotypes of Sorghum bicolor during a drought experiment in the greenhouse. We observed that root pressure was induced in plants exposed to drought followed by re-watering but possibly inhibited by 100% re-watering in some genotypes. We found that root pressure in drought stressed and re-watered plants was associated with greater ratio of fine: coarse root length and shoot biomass production, indicating a possible role of root allocation in creating root pressure and adaptive benefit of root pressure for shoot biomass production. Using RNA-Seq, we identified gene transcripts that were up- and down-regulated in plants with root pressure expression, focusing on genes for aquaporins, membrane transporters, and ATPases that could regulate inter- and intra-cellular transport of water and ions to generate positive xylem pressure in root tissue. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aims: Sand-fixing shrub Salix gordejevii plays an important role in sand dune stabilization but often shows severe decline and mortality on the windward slopes of active dunes. The objective of this study was to explore the environmental drivers and physiological mechanisms behind its decline and mortality on the windward slopes of active sand dunes. Methods: The xylem hydraulics, sap flow, water relations and non-structural carbohydrate reserves were measured for S. gordejevii plants that respectively inhabited interdune, leeward and windward positions of active dunes with contrasting soil water regimes. Results: Root exposure caused by wind erosion, rather than low soil moisture, predisposed windward S. gordejevii plants to stronger water stress. Correspondingly, the windward plants showed reduced transpirational water use and exhibited a suite of acclimative adjustments in leaf traits favoring water conservation. Despite these adjustments, windward S. gordejevii plants still suffered from higher risks of hydraulic failure and branch mortality. No evidence of carbon depletion in windward S. gordejevii plants was found although the soluble sugar to starch ratios changed significantly. Conclusions: Our findings suggest that wind-erosion-induced root exposure triggers water stress and eventually causes the mortality of windward S. gordejevii plants, during which increased risk of hydraulic dysfunction is pronounced. [ABSTRACT FROM AUTHOR]

Pistachio nuts are an economically important commodity produced by many countries. They can be colonized by mycotoxigenic fungi, especially Aspergillus flavus , resulting in contamination with aflatoxins (AFs) , especially aflatoxin B1 (AFB1), a Class 1a carcinogen. The objectives were to examine the effect of interactions between the two key abiotic factors, temperature and water activity (a w ) on (a) in vitro growth and AFB1 production by four strains of A. flavus isolated from pistachio nuts, on a milled pistachio nut medium modified ionically (NaCl) and non-ionically (glycerol) in the range 20–35°C and 0.995–0.85 a w , (b) colonization of layers of raw pistachio nuts stored at different interacting temperature x a w conditions and on relative AFB1 production and (c) develop models to produce contour maps of the optimal and marginal boundary conditions for growth and AFB1 production by up to 4 strains of this species. On pistachio nut-based media, optimum growth of four strains of A. flavus was at 0.98–0.95 a w and 30–35°C. Optimum AFB1 production was at 30–35°C and 0.98 a w . No significant differences in growth was found on ionic and non-ionically modified media. Colonization of layers of raw pistachio nuts was slower and contamination with AFB1 significantly less than in in vitro studies. Contour maps based on the pooled data for up to four strains (in vitro , in situ) showed the optimum and marginal conditions for growth and AFB1 production. These data can be used to identify those conditions which represent a high, intermediate or low risk of colonization and AFB1 contamination in the pistachio nut processing chain. These results are discussed in the context of the development of appropriate intervention strategies to minimize AFB1 contamination of this economically important commodity. [ABSTRACT FROM AUTHOR]

The recent challenge in agriculture is producing more yields by consuming less water, especially in areas with limited resources of land and water. The study was carried out at Sakha Agricultural Research station., kafr el- sheikh governorate, Egypt, during the 2018 and 2019 summer seasons to evaluate productivity and economic profitability of cowpea intercrop with maize under different sowing dates of cowpea as well as evaluate the efficiency of the system using the land equivalent ratio (LER), water equivalent ratio (WER), some water relations also Gross return. The split-plot design with three replications was used. The main plots were assigned to the cowpea sowing date (D1-1st May, D2 - 20th May, and D3- 9th June), the sub-plot was contained to the intercropping pattern (P1-(1:1), P2-(1:2) and P3-(2:4)). The highest values of irrigation water use efficiency (IWUE) and crop water use efficiency (CWUE) were given with the first sowing date under the intercropping system (1:2). The cowpea sowing dates had no significant differences in yield and some components of maize and on its interaction with intercropping patterns. The highest LER was found with the third sowing date for cowpea under intercropping system (1:2) treatment in two seasons, respectively. In economic viewpoint high additional increase in profits over each cost for all intercropping patterns especially the third sowing date for cowpea under the intercropping system (1:2). [ABSTRACT FROM AUTHOR]

A field trial was conducted at Sakha Agricultural Research Station, Kafr El – Sheikh Governorate (310 07ˉ N Latitude and 300 57ˉ E longitude with an elevation of about 6 mean sea level MSL), Egypt, during the two growing seasons of 2017 and 2018 to study the effect of sowing dates, plant density, and intercropping on yield and some yield attributes of cotton and sesame. Cotton (Gossypium barbadense L.) and sesame (Sesamum indicum) were sole cropped and intercropped at three sowing dates (April 15th (S1), April 30th (S2) and May15th (S3)) and two densities (33% (D1) and 50% (D2) of sole crop) with sesame. The experiment was laid out in randomized completely block design with split plot design with three replications. sowing date of sesame were randomized in main plots and plant density of sesame in subplots. The highest amount of applied water (AW) and water consumptive use (CU) were recorded under the first sowing date, while the highest productivity of irrigation water (PIW) and water productivity (WP) were recorded at the third sowing date and 33% density for sesame. Sowing dates had nonsignificant effect on all traits in cotton except seed yield /plant at the second season that was significant but seed yield /fed was significant of both two seasons, while, nonsignificant effect on all traits in sesame except seed yield /plant was significant at two seasons. Plant densities were highly significant effect on all traits in cotton except plant height at two seasons. And boll weight at the first season, while, significant effect on all traits in sesame except no. of branches /plant that was in significant and seed yield /plant was significant at two seasons. The highest land equivalent ration (LER) were obtained 1.41, 1.40, respectively as mean of both two seasons. The highest mean net incomes were (30120 and 27688 L.E.) obtained from sowing date 3 (May15th) and density 1(33%) of sesame in the first and second seasons, respectively. [ABSTRACT FROM AUTHOR]

Organic residues (compost) can be used as growth medium but may contain phytotoxic ions that, combined with a water deficit may alter the behavior of plants. The experiment was carried out in a growth chamber with Cistus albidus in a commercial substrate, C (sphagnum peat, coconut fiber and perlite, 8:7:1) and a mixture of compost substrates, Cp (slurry compost, coconut fiber and perlite, 3:6:1). Plants were grown in pots under well-watered, maintaining values of Ψ l around −0.9 MPa (WW) and water-stressed (WS) conditions, where the irrigation was removed until reached values of Ψ l around −3.0 MPa (water stress period), after then, water was re-established in all plants (recovery period). Although, the well-watered plants had a leaf water potential (Ψ l) around −0.9 MPa, stomatal conductance (g s) was 125 mmol m−2s−1 in the commercial substrate and 30 mmol m−2s-1 in compost. The time taken to reach the threshold value at which water stress occurs was 13 days in the commercial substrate and 53 days in compost. Water-stressed plants in the commercial substrate had significantly lower values of Ψ l and g s than well-watered. Plants in compost maintained values of g s similar in both irrigation treatments (WW and WS) and accumulated less biomass than those that grown in commercial. The water stress in compost led an increase in the adaxial epidermis, parenchyma and mesophyll, whereas water stress in commercial the proportions of the different tissues decreased. Higher lipid peroxidation values were found in plants grown in both substrates under water stress. The recovery time of the plants, until manage Ψ l values around −0.9 MPa, depended on the type of substrate. The restoration of irrigation in commercial substrate act as a new stress, as reflected in the photochemical mechanisms. • Heavy elements in compost affect plant growth, even in well-watered conditions. • Stomatal conductance vs water status depends on the substrate. • Severe water stress is slower to develop in plants grown in compost. • The time needed by plants to recover depends on the type of substrate. • The restoration of irrigation act as a new stress. [ABSTRACT FROM AUTHOR]

The saline character of water imposes restrictions on plant growth and survival in the Taklamakan Desert, China. Experiments were conducted on woody plant species, Tamarix ramosissima, Populus euphratica, and Haloxylon ammodendron grown under different levels of salinity to elucidate their adaptation to a saline environment. H. ammodendron accumulated large amounts of Na+ and Cl- in leaves. P. euphratica restricted redundant Na+ and Cl- transport to the shoots treated with lower NaCl concentrations. Na+ in leaves of T. ramosissima accumulated significantly only under higher NaCl concentrations (= 200 mM NaCl). The analyzed plants' exposure to high saline concentrations induced oxidative stress as evidenced by the increase of H2O2 and malondialdehyde and changes in photosynthetic pigments, gas-exchange characteristics, and antioxidant enzyme activities. T. ramosissima and H. ammodendron exhibited a greater ability to adapt to saline-induced oxidative stress due to more efficient antioxidant enzyme system to prevent oxidative damage. [ABSTRACT FROM AUTHOR]

• The responses of plants to drought require a fine and joint regulation of nutrients and water channels and transporters. • The gene modulation is coordinated by a network of signals which include Ca2+, ROS, and ABA. • Three different levels of responses of plants, immediate, short term and long term are proposed. Drought stress is one of the major abiotic factors affecting the growth and development of crops. The primary effect of drought is the alteration of water and nutrient uptake and transport by roots, related essentially with aquaporins and ion transporters of the plasma membrane. Therefore, the efficiency of water and nutrient transport across cell layers is a main factor in tolerance mechanisms. The regulation of this transport under water stress - in relation to the differing degrees of tolerance of crops and the effect of arbuscular mycorrhizae, together with signaling mechanisms - is reviewed here. Three different phases in the response to stress (immediate, short-term and long-term), involving different signals and levels of gene regulation, are highlighted. [ABSTRACT FROM AUTHOR]

Water deficiency, one of the major consequences of global climate change has threatened the plant growth and productivity in many parts of the world. Among different strategies being used to combat the negative effects of water deficiency on plants, exogenous application of growth regulators has emerged an effective shotgun approach. The current study has been conducted to find out whether as well as upto what extant foliar application of lysine, iron sulphate and iro-lysine complex is helpful in reducing the negative effects of water deficiency on wheat. Four levels (0.01, 0.1, 1.0 and10 mM) of each of mentioned growth regulators along with control were applied on two wheat genotypes, FSD=08 and BARS-09 under water deficit environment. The results revealed that foliar application of plant growth regulators significantly reduced the negative effects of water deficit on plant growth related attributes, like plant fresh as well as dry matter, above ground plant height, tiller and leaves. Application of all the three compounds also helped plants to maintain leaf relative water contents. Foliar supply of iron-lysine complex proved to be more useful in mitigating negative effects of water deficit on growth and water relation attributes of wheat than lysine or iron sulphate. Moreover, application of 10 mM iron-lysine complex showed more positive effects on plant growth and water relation related attribute than all other levels used in the study. [ABSTRACT FROM AUTHOR]

Periploca angustifoliaLabill., is a multipurpose shrub also used to rehabilitate drylands. It is essential to understand its phenological patterns under arid conditions. In order to understand how plants manage extreme drought, this study investigates the relationship between phenological traits of P. angustifolia Labill., water potential and climatic conditions. During two successive growing seasons (Sep 2009–Augst 2011) phenological patterns, soil water content and water potentials were measured monthly for plants of Periploca angustifoliaLabill growing under rain‐fed conditions (Annual rainfall = 168 mm) at the pastoretum of the Arid Regions Institute in southern Tunisia. The Ψmd decreased progressively and concomitantly with increasing seasonal drought, reaching the lowest values in late summer (down to –3 MPa). Water potentials of P. angustifoliaLabill were affected by spatial and temporal variations in soil water content. The increased diurnal amplitude values (∆ψ > −1.3 MPa) explained the especially high biological activity of this species during the dry season. Our results clearly demonstrate that P. angustifolia Labill is a drought‐tolerant species reaching low water potentials during the driest months of summer. These characteristics make this shrub as promising for rehabilitating degraded arid ecosystems. [ABSTRACT FROM AUTHOR]

Aim: We investigated how substrate hydraulic properties respond to the presence of arbuscular mycorrhizal fungi (AMF) in root-containing and root-free substrate zones in a Medicago truncatula-Rhizophagus irregularis model system. Methods: Before planting, two compartments constructed from standard soil sampling cores (250 cm3) were implanted into non-mycorrhizal and mycorrhizal pots containing a sand-zeolite-soil mix. One compartment allowed root penetration (1 mm mesh cover) and the other only hyphal ingrowth (42 μm mesh cover). After eight weeks of growth under maintenance of moist conditions, the cores were subjected to water retention measurements. Additionally, we measured water retention of bare substrates before and after drying events to check for successful maintenance of moist conditions in pots. Results: Drying of bare substrates decreased water retention, but planting at least sustained it. The parameters of water retention models responded linearly to root morphological traits across mycorrhizal and non-mycorrhizal substrates. Hyphae-only colonization comparatively affected the course of water retention in ways that suggest increased pore space heterogeneity while maintaining water storage capacity of substrates. Conclusions: Hence, water contents corresponded to different substrate matric potentials in non-mycorrhizal and mycorrhizal pots. We conclude that changes to water retention in AMF colonized substrates can contribute to a widely observed phenomenon, i.e. that mycorrhizal plants differ in their moisture stress response from non-mycorrhizal plants. [ABSTRACT FROM AUTHOR]

Wintergreen fern Polystichum acrostichoides has fronds that are photosynthetically active year-round, despite diurnal and seasonal changes in soil moisture, air temperature and light availability. This species can fix much of its annual carbon during periods when the deciduous canopy is open. Yet, remaining photosynthetically active year-round requires the maintenance of photosynthetic and hydraulic systems that are vulnerable to freeze–thaw cycles. We aimed to determine the anatomical and physiological strategies P. acrostichoides uses to maintain positive carbon gain, and the coordination between the hydraulic and photosynthetic systems. We found that the first night below 0 °C led to 25 % loss of conductivity (PLC) in stipes, suggesting that winter-induced embolism occurred. Maximum photosynthetic rate and chlorophyll fluorescence declined during winter but recovered by spring, despite PLC remaining high; the remaining hydraulic capacity was sufficient to supply the leaves with water. The onset of colder temperatures coincided with the development of a necrotic hinge zone at the stipe base, allowing fronds to overwinter lying prostrate and maintain a favourable leaf temperature. Our conductivity data show that the hinge zone did not affect leaf hydraulics because of the flexibility of the vasculature. Collectively, these strategies help P. acrostichoides to survive in northeastern forests. [ABSTRACT FROM AUTHOR]

Vesicular trichomes play a key role in excluding toxic ions from some halophyte species, preventing the essential processes and functions of plants from being altered. Thus, the present study aimed to evaluate the influence of these structures on Atriplex nummularia irrigated using waters with three levels of osmotic potential (−0.1, −1.4 and −2.7 MPa), formulated with NaCl in plants with vesicular trichomes and plants with partial removal of trichomes. The experiment was conducted in a protected environment and plants were evaluated for physiological parameters (water, osmotic and pressure potentials, relative water content, osmotic adjustment, pressure-volume curve, gas exchange), electrolyte leakage, lipid peroxidation and enzymatic activity (superoxide dismutase, ascorbate peroxidase, catalase). The results obtained made it possible to identify the strong contribution of vesicular trichomes to physiological and biochemical parameters, with indication of cell wall stiffening and maintenance of turgor. Furthermore, the evaluation of the osmotic potentials obtained in the study suggests that the contribution of vesicular trichomes to the salinity tolerance of the species is greater than that of osmotic adjustment. Furthermore, gas exchange results suggest that the presence of trichomes was able to regulate stomatal processes so that the plant maintains its photosynthetic performance. Evaluation of electrolyte leakage, together with the increase in malondialdehyde content, showed that the maintenance of trichomes reduces the probability of oxidative stress. The activity of antioxidant enzymes was efficient in eliminating reactive oxygen species, especially the activity of ascorbate peroxidase, which stood out in terms of hydrogen peroxide detoxification. • Vesicular trichomes play a key role in excluding toxic ions. • Irrigation with saline water contributes to cell wall rigidity. • Maintenance of trichomes helps maintain photosynthetic efficiency. • Presence of trichomes reduces the occurrence of oxidative stress. [ABSTRACT FROM AUTHOR]

Water scarcity is one of the most pressing and threating environmental issues facing the human population. Plant growth promoting bacteria (PGPB) are presented as safe and ecological complementary solution to the food security problem along with the traditional crop breeding and genetic engineering. Plant-associated microbial communities, such as, nitrogen-fixing bacteria, improve crop productivity and provide stress tolerances for different biotic and abiotic factors. In this study, we isolated and characterized fourteen Azotobacter spp from rhizosphere of wheat plants, among these isolates; we identified the most effective plant growth promoting isolate as Azotobacter chroococcum using Bio-log identification system. The encapsulated of the A. chroococcum with sodium alginate shows beds integrity intact bacterial cells using the scanning electron microscopy. Encapsulated A. chroococcum was tested for growth promotion of wheat under different water regime at field experiments, the results indicated that encapsulated A. chroococcum was effective in lowering the harmful effect of water deficit on several wheat agronomical criteria. Wheat treated with encapsulated or liquid culture significantly diminish the reductions in relative water content recorded 66.37% and 59.23%, respectively under water defiant 80% from actual evapotranspiration plus 100% and 75% mineral nitrogen. Moreover, wheat inoculated with A. chroococcum in two forms showed reduction in proline accumulations in shoots, as well as lowest antioxidant enzymes contents. The inoculation with A. chroococcum either encapsulated or liquid culture significantly enhanced wheat grain yield and yield components, as well as nitrogen (N), phosphorus (P), and potassium (K) contents in grains of wheat under water defiant 80% from actual evapotranspiration. [ABSTRACT FROM AUTHOR]

Premise of research. Although the term "pseudobulb" has been used in the literature on Orchidaceae for almost two centuries, no definition establishes unambiguous criteria to distinguish such a succulent shoot from a "normal" stem. It is currently impossible to decide whether variation is continuous rather than categorical. Methodology. We studied three morphological characteristics (succulence index, deviation from spherical shape, and proportion of lignified tissue in cross sections) in stems of 89 orchid species. Pivotal results. Shape as such did not allow us to separate groups: variation was continuous in our data set. However, a cluster analysis of all three traits separated species with normal stems from those with thickened stems. Within the latter group, two subgroups emerged: a relatively homogeneous subgroup of species with rather globose, mostly heteroblastic pseudobulbs and a morphologically and anatomically much more diverse second subgroup of species with homoblastic stems. A second part of the study assessed ontogenetic changes in stem shape. In the majority of cases, stem shape changed substantially from sometimes almost spherical in small juveniles to elongated in larger individuals. This pattern, although much more pronounced in species with normal stems, was also found in certain species with pseudobulbs. While water storage capacity in the smallest plants is maximized relative to the transpiring surface, the increased absolute water storage capacity of larger plants relaxes the selective pressure to depart more and more from a spherical shape. Conclusions. Although some ambiguity remains, the results of our quantitative approach confirm the usefulness of the pseudobulb concept. However, we identify a large, quite heterogeneous group of species with intermediate traits between those of normal stems and pseudobulbs. [ABSTRACT FROM AUTHOR]

Aims: The objective was to clarify the role of root water transport in waterlogged canola plants. We examined the hypothesis that waterlogging triggers root suberization and lignification, which reduces the effectiveness of apoplastic bypass and increases the dependence of roots on the aquaporin-mediated water transport, and that this effect varies depending on the growth stage. Methods: Brassica napus plants at the seedling, flowering and podding growth stages were waterlogged for up to 8 days. Growth, gas exchange, leaf water potentials, and root hydraulic conductance were measured in addition to relative contributions of the aquaporin-mediated and apoplastic root water transport, gene expression levels of plasma membrane intrinsic proteins (BnPIPs), and lignin and suberin deposition in roots. Results: Waterlogging decreased dry weights, gas exchange, leaf water potentials and root hydraulic conductivity more in plants at the seedling stage than other growth stages. It also accelerated root suberization and lignification resulting in an increase of a relative contribution of aquaporin-mediated water transport. The transcript levels of BnPIPs increased with an increasing duration of waterlogging. Conclusions: Effects on root water transport played an important role in the sensitivity of canola seedlings to waterlogging. Increased relative contribution of aquaporin-mediated water transport in waterlogged plants was accompanied by enhanced root suberization and lignification. The evidence points to the importance of maintaining functional aquaporins in plant survival of waterlogging. [ABSTRACT FROM AUTHOR]

The application of microorganisms in crops has been proposed as a strategy to cope with adverse environmental conditions. Two separate experiments (I and II) were carried out in laurustinus plants in field conditions. For each experiment, half of the plants were irrigated with control water (C, EC <0.9 dS m−1) and the other half with reclaimed wastewater (RW, EC: 6 dS m−1). In experiment I, for each irrigation treatment, half of the plants were inoculated with Glomus iranicum (AMF). In experiment II, for each irrigation treatment, half of the plants were inoculated with a rhizosphere microbial complex (RMC). In experiment I, AMF increased leaf Ca/Na ratio and reduced leaf Cl concentration. In addition, stem water potential was enhanced in plants subjected to RW. Stomatal conductance was also improved by AMF in plants subjected to C and RW treatments. In experiment II, leaf K/Na and Ca/Na ratios were increased and leaf Cl concentration was reduced by RMC. The RMC increased stem water potential and relative chlorophyll content in both irrigation treatments. Under RW irrigation, plants with RMC showed better leaf stomatal conductance. These results highlight the importance of studying the microorganisms/species interaction in order to select the best combination. [ABSTRACT FROM AUTHOR]

Crop production in arid regions requires continuous irrigation to fulfill water demand throughout the growing season. Agronomic measures, such as roots-soil microorganisms, including arbuscular mycorrhizal (AM) fungi, have emerged in recent years to overcome soil constraints and improve water use efficiency (WUE). Eggplant plants were exposed to varying water stress under inoculated (AM+) and non-inoculated (AM-) to evaluate yield performance along with plant physiological status. Plants grown under full irrigation resulted in the highest fruit yield, and there were significant reductions in total yield and yield components when applying less water. The decline in fruit yield was due to the reduction in the number of fruits rather than the weight of the fruit per plant. AM+ plants showed more favorable growth conditions, which translated into better crop yield, total dry biomass, and number of fruits under all irrigation treatments. The fruit yield did not differ between full irrigation and 80% evapotranspiration (ET) restoration with AM+, but a 20% reduction in irrigation water was achieved. Water use efficiency (WUE) was negatively affected by deficit irrigation, particularly at 40% ET, when the water deficit severely depressed fruit yield. Yield response factor (Ky) showed a lower tolerance with a value higher than 1, with a persistent drop in WUE suggesting a lower tolerance to water deficits. The (Ky) factor was relatively lower with AM+ than with AM+ for the total fruit yield and dry biomass (Kss), indicating that AM may enhance the drought tolerance of the crop. Plants with AM+ had a higher uptake of N and P in shoots and fruits, higher stomatal conductance (gs), and higher photosynthetic rates (Pn), regardless of drought severity. Soil with AM+ had higher extractable N, P, and organic carbon (OC), indicating an improvement of the fertility status in coping with a limited water supply. [ABSTRACT FROM AUTHOR]

Copyright of Revista Colombiana de Ciencias Hortícolas is the property of Revista Colombiana de Ciencias Horticolas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize (Zea mays L.) plays an important role in the global food security, but its production is threatened by climate change, especially drought stress. Potassium (K) and zinc (Zn) are considered useful to mitigate the negative consequences of drought stress in plants. Therefore, the objective of this two-year study was to identify the best combination of K and Zn application to improve the water relations, photosynthetic pigments, yield, irrigation water use efficiency (IWUE) and grain quality of maize sown under mild and severe drought stress conditions. The consisted of three drought stress levels viz. 1) well-watered as control (WW), 2) mild drought (MD) with 25 mm of potential soil moisture deficit (PSMD), 3) severe drought (SD) with 50 mm of PSMD and six K-Zn treatments: i.e. 125, 100 and 150 kg ha−1 K with 0 and 12 kg ha−1 Zn. The results indicated that K-Zn application improved the water relations and chlorophyll contents, biological yield and grain quality, irrespective of water stress treatment. The combined application of K-Zn under mild drought stress produced statistically same biological yield and grain quality as under well-irrigated without K-Zn fertilization and also produced compratively higher IWUE, biological yield and grain quality under sverer drought stress. Hence, the application of K at 150 kg ha−1 in combination with Zn at 12 kg ha−1 might be useful to improve the maize production and grain quality under drought stress. As IWUE was low in WW conditions, therefore, irrigation scheduling must be re-evaluated for optimum water use efficiency. [ABSTRACT FROM AUTHOR]

Drought is a burning issue all over the world that has led to remarkable reductions in the growth and yield of crops. Based upon the current problem, a series of two rain out shelter pot research experiments were performed to evaluate the drought tolerance in canola by foliar application of potassium (K) under water deficiency conditions in the Department of Agronomy, University of Agriculture Faisalabad, Pakistan. Four varieties of canola (Faisal Canola, Cyclone, Shiarlae, and Dunkled) were tested under two water deficit levels (100% FC and 50% FC) and two treatments of foliar potassium application i.e., 0% K and 2% K. The data was recorded with standard procedures when the plants were grown up to maturity. Results concluded that drought posed a significant decrease in all parameters under study. However, supplemental foliar application of potassium at the rate of 2% at both (vegetative and reproductive) stages of canola enhanced the water potential (0.24% and 0.23%), osmotic potential (0.12% and 0.11%), turgor pressure (0.66% and 0.58%), respectively. Similarly, the chlorophyll contents as chlorophyll a (0.25% and 0.28%), chlorophyll b (1.26% and 1.80%) and leaf carotenoid contents (0.20% and 0.62%) were also increased where K was applied at the rate of 2% during vegetative and reproductive stages of canola. The foliar applied K at the rate 2% enhanced leaf photosynthetic rate (13.11 µmol CO2 m−2 s−1 and 15.96 µmol CO2 m−2 s−1), transpiration rate (5.36 µmol CO2 m−2 s−1 and 5.54 µmol CO2 m−2 s−1) and stomatal conductance (0.22 µmol CO2 m−2 s−1 and 0.26 µmol CO2 m−2 s−1) of the plants at both stages. Yield attributes such as thousand seed weight (1.03% and 1.03%), seed yield (0.58% and 0.58%) and biological yield (0.35% and 0.38%) were increased by foliar K application under water deficit conditions at both stages. The genotype Shiralae showed significant improvement among all others genotypes under normal as well as water deficit conditions [ABSTRACT FROM AUTHOR]

Purpose: To elucidate the effects during the vegetative growth of pre-sowing magnetic treatments on water relations, photosynthesis and plant growth in tomato (Vyta) plants under greenhouse conditions. Materials and methods: Tomato seeds were exposed to full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 120 mT (rms) for 10 min and at 80 mT (rms) for 5 min. Non-treated seeds were used as controls. Plants were grown in polystyrene trays and water relations, photosynthesis and plant growth were measured. Results: Plants from magnetically treated seeds maintained better leaf water status in terms of increases in leaf water potential, leaf osmotic potential, leaf turgor potential and relative water content, and decreases in stomatal conductance and transpiration rate. Net photosynthesis rate, chlorophyll a, chlorophyll b, carotenoids and total chlorophyll contents increase in plants from magnetically exposed seeds compared to controls. The MF treatments lead to a notable increase in root length, plant height, root and shoot dry mass, leaf area per plant, and root and shoot relative growth rates. Conclusions: Application of full-wave rectified sinusoidal non-uniform MF as a pre-sowing treatment has the potential to improve tomato plant vegetative growth through the enhancement of water relations and photosynthesis. [ABSTRACT FROM AUTHOR]

To investigate the effects of salinity stress on canola, ten cultivars of spring canola obtained from Karaj Seed and Plant Improvement Institute, were evaluated in vegetative growth stage in the greenhouse of Payam-e- Noor University of Mahabad, in 2017. The experiment was carried out in two salinity levels of Sodium Chloride (zero (control) and 250 mM) using a hydroponic system. Traits were measured at the end of rosette and before the stem elongation stages, after two weeks of salinity stress. The results showed that in addition to morphological depreciation, salinity stress caused imbalance in ionic concentration, increased Na+ concentration, and decreased K+ and K+/Na+. Meanwhile amount of the electrolyte leakage, proline and glycine betaine was higher under stress than control condition while the RWC was decreased. Generally, the most tolerant and succeptible cultivars were SW5001 and Sarigol respectively. Traits such as plant dry weight, chlorophyll index and K+/Na+ were 10.89, 41.53 and 16.80 respectively in tolerant SW5001 cultivar and were of 8.70, 38.10 and 8.25, respectively in Sarigol succeptible variety. Therefore, there was diversity between the studied cultivars in terms of response to salinity stress, which could be used in complementary studies and ultimately in plant breeding programs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sociality has evolved independently many times in a diverse array of animal taxa. While sociality in some invertebrates, birds and mammals is relatively well understood, complex social behaviour in Squamate reptiles is a comparatively recent discovery. The extent to which social behaviour is phylogenetically constrained, or free to respond to environmental conditions is a key question in understanding sociality. We sampled 74 aggregations involving 137 individuals of a social lizard (Egernia stokesii) from 13 sites across a 96 250 km2 area showing a wide range of environmental conditions. Over all locations, 70% of the lizards were found in aggregations, supporting the previous suggestion that aggregation in this species is phylogenetically constrained. However, the size of aggregations was negatively related to spatial variation in aridity and daily variation in maximum temperature, suggesting that social behaviour also varied in response to harsh environmental conditions. Lizards aggregated more in arid areas and on cold days. Our results show that it is overly simplistic to regard social behaviour in E. stokesii as either phylogenetically constrained or environmentally determined. A more nuanced appreciation of the extent to which social behaviour is free to vary in response to environmental conditions improves our understanding of social behaviour in Squamate reptiles. [ABSTRACT FROM AUTHOR]

Differences in key physiological characteristics between plant species can result in their contrasting performances in vegetation restoration projects, but ecophysiological comparative studies in close relation to ecological restoration projects are scarce. Hedysarum fruticosum Pall. and Caragana microphylla Lam. are two leguminous shrub species widely used in combination for fixation of active sand dunes in semiarid regions of northern China, but they clearly differ in fitness at different stages of dune vegetation development; that is, H. fruticosum quickly gains a community dominance at the initial stage but yields to C. microphylla in a few years after the fixation of dunes. To reveal the underlying mechanism of such a pattern, key physiological characteristics related to xylem water transport, leaf water use, and drought tolerance were compared between these two species at a typical site of sand dune fixation project in Inner Mongolia. Compared with C. microphylla, H. fruticosum shows an acquisitive and risky water management strategy with substantially higher hydraulic efficiency and photosynthetic capability but reduced resistance to drought‐induced xylem embolism, which endows it an advantage under conditions of relatively high soil water availability at the early stage of dune fixation. In contrast, C. microphylla exhibits more conservative water use and characteristics of greater drought tolerance, which results in greater dominance under the more drought‐stressed conditions of the later stage of dune fixation. Our study for the first time provides a potential mechanistic explanation for the clear switching of dominant positions between the two important sand‐fixing shrub species during the sand dune revegetation process. [ABSTRACT FROM AUTHOR]

Juniperus californica (California juniper; Cupressaceae) occurs in a variety of habitats, including pinyon-juniper woodlands and high elevation desert scrub in the northwestern Sonoran Desert. The goal was to determine how much physiological and structural plasticity and microclimate allow J. californica to survive in desert scrub. We hypothesized that individuals in the desert scrub (Agave Hill) coped with greater water stress by limiting xylem cavitation and exhibiting greater stomatal control than individuals in the pinyon-juniper woodland (Pinyon Crest). Additionally, J. californica were expected to occur in cooler microhabitats in the desert scrub, which should have more available soil water than the surroundings. Hypotheses were tested by examining climate data, as well as the morphology, physiology, wood anatomy, and canopy and soil temperatures for individuals at both sites. Agave Hill received less rainfall and the air and soil temperatures were significantly warmer than at Pinyon Crest. Individuals were larger at Pinyon Crest than at Agave Hill; however, water relations and maximum quantum efficiency of Photosystem II did not differ between sites. Plants at Agave Hill had lower CO2 uptake in the autumn and suffered greater dieback during the study; stomatal conductance was also lower at Agave Hill. Average native xylem embolism and wood anatomy did not differ with site; however, xylem embolism did increase as plant shoot volume decreased at Agave Hill. The results indicate that J. californica exists in desert scrub by occupying washes and altering its morphology through reduced growth and dieback during stressful periods. [ABSTRACT FROM AUTHOR]

Microbial growth in vase solutions and ethylene damage are often associated with premature senescence in cut flowers. We examined the efficacy of Scutellaria baicalensis Georgi extract (SC) to improve postharvest longevity and quality of two cut roses (Rosa hybrida L.) 'Jinny' and 'Wild Look' to develop an inexpensive and innocuous preservative solution for the cut flower industry. Pretreatments with 100, 200, 300, and 500 μL L−1 SC effectively extended the vase life of the cut rose cultivars. Among the tested pretreatments, 300 μL L−1 of SC was the most effective concentration and significantly prolonged the postharvest longevity of cut flowers from 11.8 days (control) to 17.4 days in 'Jinny' and from 13.6 (control) to 20.9 days in 'Wild Look'. The beneficial effects of 300 μL L−1 SC pretreatment inhibited bacterial accumulation at the base of the cut stems, enhanced water uptake, and maintained initial fresh weight, positive water balance, and chlorophyll fluorescence (Fv/Fm) in the leaves of cut roses. In addition, 300 μL L−1 SC pretreatment suppressed the transcript levels of ethylene biosynthesis genes (RhACO1, RhACS1, RhACS3, and RhACS4) in rose petals and delayed flower senescence. The efficacy of 300 μL L−1 SC pretreatment in extending the vase life of cut roses was equal to 0.1 mM silver thiosulfate (STS), and greater than hydrosol (H), H + SC, and H + sucrose (H + Suc). Therefore, the results from our study highlight the potential of SC as an alternative preservative in the cut rose industry. [ABSTRACT FROM AUTHOR]

Carnation (Dianthus caryophyllus L.) and chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitam.] cut flowers are among the most important commodities that dominate flower markets throughout the world. Two major problems in the transportation and marketing of these flowers are their relatively short vase life and the rapid decline of their aesthetic value. In this respect, the current study investigates the effects of silver nanoparticles (AgNPs) on ethylenesensitive (carnation) and ethyleneinsensitive (chrysanthemum) cut flowers. Specifically, this research examines their morphophysicochemical characteristics, antioxidant enzyme activities and vase life. Here, the AgNPs were synthesized by chemical methods and then applied on both flowers by a pulsing method. The treatments involved two concentrations of AgNPs (0.04 and 0.08 g L-1) along with the control (deionized water), and the duration of exposure lasted for 24 h. Then, the flower stems were placed in an aqueous sucrose solution (4%) until the end of the experiment. All traits, except the vase life, were evaluated after 0, 3, 6 and 9 d following the treatments during the vase period. During this time, the control groups of both flowers showed considerable amounts of decrease in the relative fresh weight (RFW), vase solution uptake (VSU), flower diameter, membrane stability index (MSI) and total soluble carbohydrate (TSC). Meanwhile, there were increases in hydrogen peroxide content (H2O2) and peroxidase (POD) activity. The bacterial population of the stem end and total soluble protein (TSP) increased in carnation petals, but decreased in chrysanthemum petals. The activity of superoxide dismutase (SOD) dropped in carnation petals, whereas it rose in chrysanthemum petals. Using AgNPs at concentrations of 0.08 and 0.04 g L-1 can optimally extend the vase life of carnation and chrysanthemum, respectively. [ABSTRACT FROM AUTHOR]

Trees of the genus Prunus produce some of the most widely consumed fruits globally. The combination of climate change-related warming and increased drought stress, scarcity of freshwater resources for irrigation, and increasing demands due to population growth creates a need for increased drought tolerance in these tree species. Recently, we have shown in the field that a native wild pear species performs better under drought than two cultivated pear species. Here, a comparative field study was conducted in Israel to investigate traits associated with drought tolerance in almond (cultivated Prunus dulcis (Mill.) D. A. Webb vs wild Prunus ramonensis Danin) and plum (cultivated Prunus domestica L. vs wild Prunus ursina Kotschy). Measurements of xylem embolism and shoot and root carbon reserves were done along a year, including seasonal drought in the wild and a 35-day drought experiment in the orchards. Synchronous measurements of native xylem embolism and shoot water potential showed that cultivated and wild almond trees lost ~50% of hydraulic conductivity at −2.3 and −3.2 MPa, respectively. Micro-CT images confirmed the higher embolism ratio in cultivated versus wild almond, whereas the two plum species were similar. Dynamics of tissue concentrations of nonstructural carbohydrates were mostly similar across species, with higher levels in cultivated versus wild plum. Our results indicate an advantage for the wild almond over its cultivated relative in terms of xylem resistance to embolism, a major risk factor for trees under drought stress. This result is in line with our previous experiment on pear species. However, the opposite trends observed among the studied plum species mean that these trends cannot be generalized. It is possible that the potential for superior drought tolerance in wild tree species, relative to their cultivated relatives, is limited to wild species from dry and hot habitats. [ABSTRACT FROM AUTHOR]