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This study sought to better understand how time of day (ToD) or turgor pressure might affect the flexural stiffness of sweet sorghum stalks and potentially regulate stalk lodging resistance. Stalk flexural stiffness measured across a 48 h period in 2019 showed a significant diurnal association with leaf water potential and stalk flexural stiffness. While the correlation between stalk flexural stiffness and this proxy for internal turgor status was statistically significant, it only accounted for roughly 2% of the overall variance in stiffness. Given that turgor status is a dynamic rather than fixed physiological variable like the cellular structure, these data suggest that internal turgor plays a small yet significant role in influencing the flexural stiffness of fully mature stalks prior to a stalk lodging event. The association was assessed at earlier developmental stages across three distinct cultivars and found not to be significant. Panicle weight and stalk basal weight, but not stalk Brix or water content, were found to be better predictors of stalk flexural stiffness than either ToD or turgor status. Observation across three cultivars and four distinct developmental stages ranging from the vegetative to the hard-dough stages suggests that stalk flexural stiffness changes significantly as a function of time. However, neither ToD nor turgor status appear to meaningfully contribute to observed variations in stalk flexural stiffness in either individual stalks or across larger populations. As turgor status was not found to meaningfully influence stalk strength or flexural stiffness at any developmental time point examined in any of the three sweet sorghum cultivars under study, turgor pressure likely offers only inconsequential contributions to the biomechanics underlying sweet sorghum stalk lodging resistance. [ABSTRACT FROM AUTHOR]

The Landauer principle sets a thermodynamic bound of k B T ln 2 on the energetic cost of erasing each bit of information. It holds for any memory device, regardless of its physical implementation. It was recently shown that carefully built artificial devices can attain this bound. In contrast, biological computation-like processes, e.g., DNA replication, transcription and translation use an order of magnitude more than their Landauer minimum. Here, we show that reaching the Landauer bound is nevertheless possible with biological devices. This is achieved using a mechanosensitive channel of small conductance (MscS) from E. coli as a memory bit. MscS is a fast-acting osmolyte release valve adjusting turgor pressure inside the cell. Our patch-clamp experiments and data analysis demonstrate that under a slow switching regime, the heat dissipation in the course of tension-driven gating transitions in MscS closely approaches its Landauer limit. We discuss the biological implications of this physical trait. [ABSTRACT FROM AUTHOR]

Turgor pressure provides the force needed to stress and deform the cell walls of plants, algae, and fungi during expansive growth. However, turgor pressure plays another subtle but equally important role in expansive growth of walled cells: it connects the two biophysical processes of water uptake and wall deformation to ensure that the volumetric rates of water uptake and enlargement of the cell wall chamber are equal. In this study, the role of turgor pressure as a 'connector' is investigated analytically by employing validated and established biophysical equations. The objective is to determine the effect of 'wall loosening' on the magnitude of turgor pressure. It is known that an increase or decrease in turgor pressure and/or wall loosening rate increases or decreases the expansive growth rate, respectively. Interestingly, it is shown that an increase in the wall loosening rate decreases the turgor pressure slightly, thus reducing the effect of wall loosening on increasing the expansive growth rate. Other analyses reveal that reducing the rate of water uptake results in a larger decrease in turgor pressure with the same increase in wall loosening rate, which further reduces the effect of wall loosening on increasing the expansive growth rate. [ABSTRACT FROM AUTHOR]

Anthracnose of poplar caused by Colletotrichum gloeosporioides is a leaf disease that seriously affects poplar growth. The pathogen invades the host in the form of adherent cells, which generate turgor pressure through the metabolism of intracellular substances prior to penetrating the epidermis of poplar leaves. In this study, the expansion-related pressure of the mature appressorium of the wild-type C. gloeosporioides was approximately 13.02 ± 1.54 MPa at 12 h, whereas it was 7.34 ± 1.23 MPa and 9.34 ± 2.22 MPa in the melanin synthesis-related gene knockout mutants ΔCgCmr1 and ΔCgPks1, respectively. The CgCmr1 and CgPks1 genes were highly expressed at 12 h in the wild-type control, implying that the DHN melanin biosynthesis pathway may play an important role in the mature appressorium stage. The transcriptome sequencing analysis indicated that the upregulated melanin biosynthesis genes in C. gloeosporioides, such as CgScd1, CgAyg1, CgThr1, CgThr2, and CgLac1, are involved in specific KEGG pathways (i.e., fatty acid biosynthesis, fatty acid metabolism, and biotin metabolism). Therefore, we speculate that the melanin synthesis-related genes and fatty acid metabolism pathway genes contribute to the regulation of the turgor pressure in the mature C. gloeosporioides appressorium, ultimately leading to the formation of infection pegs that enter plant tissues. These observations may reflect the co-evolution of C. gloeosporioides and its host. [ABSTRACT FROM AUTHOR]

Aerosols can contribute to plant nutrition via foliar uptake. The conditions for this are best at night because the humidity is high and hygroscopic, saline deposits can deliquesce as a result. Still, stomata tend to be closed at night to avoid unproductive water loss. However, if needed, nutrients are on the leaf surface, and plants could benefit from nocturnal stomatal opening because it further increases humidity in the leaf boundary layer and allows for stomatal nutrient uptake. We tested this hypothesis on P-deficient soil by comparing the influence of ambient aerosols and additional foliar P application on nocturnal transpiration. We measured various related leaf parameters, such as the foliar water loss, minimum leaf conductance (gmin), turgor loss point, carbon isotope ratio, contact angle, specific leaf area (SLA), tissue element concentration, and stomatal and cuticular characteristics. For untreated leaves grown in filtered, aerosol-free air (FA), nocturnal transpiration consistently decreased overnight, which was not observed for leaves grown in unfiltered ambient air (AA). Foliar application of a soluble P salt increased nocturnal transpiration for AA and FA leaves. Crusts on stomatal rims were shown by scanning electron microscopy, supporting the idea of stomatal uptake of deliquescent salts. Turgor loss point and leaf moisture content indicated a higher accumulation of solutes, due to foliar uptake by AA plants than FA plants. The hypothesis that deliquescent leaf surface salts may play a role in triggering nocturnal transpiration was supported by the results. Still, further experiments are required to characterize this phenomenon better. [ABSTRACT FROM AUTHOR]

Water deficits affect the capacity of leaves to transport water, a process that is related to the obstruction of air in the xylem (embolism). The tolerance to this process has been negatively associated with water-transport efficiency at the xylem level across species, suggesting a tradeoff between hydraulic efficiency and safety. But there is a lack of observation at higher integration levels, i.e., organs. This study aimed to evaluate this tradeoff across six fruit tree species with a wide range of water-stress tolerance: pomegranate, olive, fig tree, mandarin, avocado, and vine. Efficiency was represented by the maximum foliar hydraulic conductance (Kmax) and stomatal conductance, whereas hydraulic security by water potential in which the leaf loses 50% of its water-transport capacity (P50), and at the point of loss of leaf turgor (Ψtlp). Results suggest that the compensation is weak or null at the foliar level. We observed that species with higher hydraulic efficiency tend to be more tolerant to leaf dehydration (higher hydraulic safety), except mandarin, which had lower Kmax and relatively higher P50. Morphological traits associated with carbon investment dynamic (leaf mass per area and petiole density) were highly correlated to water-stress tolerance across fruit tree species. [ABSTRACT FROM AUTHOR]

Sapodilla (Achras zapota L.) is a fruit with a great nutritional potential; however, its perishable nature is a great obstacle for commercialization/exportation. Herein, osmotic dehydration was applied to sapodilla to reduce post-harvest losses and obtain a stable product with acceptable sensorial characteristics. Initially, a 2³ full-factorial design was performed to determine the effect of temperature (30–50 °C), sucrose concentration (40–60% °Brix) and immersion time (90–240 min) on the moisture loss (ML), solid gain (SG) and dehydration efficiency index (DEI). The samples with higher DEI values were subjected to sensory analysis, followed by physicochemical, microbiological and structural analyses. The temperature and the concentration of the osmotic solution had significant influence (p < 0.05) on ML and SG, whereas DEI was significantly influenced (p < 0.05) by the concentration of osmotic solution and the immersion time. The sample produced by osmotic dehydration using the optimized conditions (40 °C, 50 °Brix; 165 min) obtained higher scores on the sensorial attributes, greater compliance with microbiological standards and generated turgor reduction and ruptures of sapodilla cell walls. [ABSTRACT FROM AUTHOR]

Silicon (Si) is an abundant element which, when supplied to plants, confers increased vigor and resistance to exogenous stresses, as well as enhanced stem mechanical strength. Plant species vary in their ability to take Si up and to accumulate it under the form of silicon dioxide (SiO2) in their tissues: emblematic of this is the example of Poales, among which there is rice, a high Si accumulator. Monocots usually accumulate more Si than dicots; however, the impact that Si has on dicots, notably on economically important dicots, is a subject requiring further study and scientific efforts. In this review, we discuss the impact that Si has on bast fibre-producing plants, because of the potential importance that this element has in sustainable agriculture practices and in light of the great economic value of fibre crops in fostering a bio-economy. We discuss the data already available in the literature, as well as our own research on textile hemp. In particular, we demonstrate the beneficial effect of Si under heavy metal stress, by showing an increase in the leaf fresh weight under growth on Cd 20 μM. Additionally, we propose an effect of Si on bast fibre growth, by suggesting an action on the endogenous phytohormone levels and a mechanical role involved in the resistance to the turgor pressure during elongation. We conclude our survey with a description of the industrial and agricultural uses of Si-enriched plant biomass, where woody fibres are included in the survey. [ABSTRACT FROM AUTHOR]

Water-transport pathways through the leaf are complex and include several checkpoints. Some of these checkpoints exhibit dynamic behavior that may be regulated by aquaporins (AQPs). To date, neither the relative weight of the different water pathways nor their molecular mechanisms are well understood. Here, we have collected evidence to support a putative composite model of water pathways in the leaf and the distribution of water across those pathways. We describe how water moves along a single transcellular path through the parenchyma and continues toward the mesophyll and stomata along transcellular, symplastic and apoplastic paths. We present evidence that points to a role for AQPs in regulating the relative weight of each path in the overall leaf water-transport system and the movement of water between these paths as a result of the integration of multiple signals, including transpiration demand, water potential and turgor. We also present a new theory, the hydraulic fuse theory, to explain effects of the leaf turgor-loss-point on water paths alternation and the subsequent reduction in leaf hydraulic conductivity. An improved understating of leaf water-balance management may lead to the development of crops that use water more efficiently, and responds better to environmental changes. [ABSTRACT FROM AUTHOR]

Successful management of forest systems requires a deeper understanding of the role of ecophysiological traits in enabling adaptation to high temperature and water deficit under current and anticipated changes in climate. A key attribute of leaf water relations is the water potential at zero turgor (πtlp), because it defines the operating water potentials over which plants actively control growth and gas exchange. This study examines the drivers of variation in πtlp with respect to species climate of origin and habitat water availability. We compiled a water relations database for 174 woody species occupying clearly delineated gradients in temperature and precipitation across the Australian continent. A significant proportion of the variability in πtlp (∼35%) could be explained by climatic water deficit and its interaction with summertime maximum temperature, demonstrating the strong selective pressure of aridity and high temperature in shaping leaf water relations among Australian species. Habitat water availability (midday leaf water potential), was also a significant predictor of πtlp (R² = 0.43), highlighting the importance of species ecohydrologic niche under a set of climatic conditions. Shifts in πtlp in response to both climatic and site-based drivers of water availability emphasises its adaptive significance and its suitability as a predictor of plant performance under future climatic change. [ABSTRACT FROM AUTHOR]

The devastating fungus Magnaporthe oryzae (M. oryzae) forms a specialized infection structure known as appressorium, which generates enormous turgor, to penetrate the plant cells. However, how M. oryzae regulates the appressorium turgor formation, is not well understood. In this study, we identified MoBZIP3, a bZIP transcription factor that functioned in pathogenesis in M. oryzae. We found that the pathogenicity of the MoBZIP3 knockout strain (Δmobzip3) was significantly reduced, and the defect was restored after re-expression of MoBZIP3, indicating that MoBZIP3 is required for M. oryzae virulence. Further analysis showed that MoBZIP3 functions in utilization of glycogen and lipid droplets for generation of glycerol in appressorium. MoBZIP3 localized in the nucleus and could bind directly to the promoters of the glycerol synthesis-related genes, MoPTH2, MoTGL1 and MoPEX6, and regulate their expression which is critical for glycerol synthesis in the appressorium turgor pressure generation. Furthermore, the critical turgor sensor gene MoSln1 was also down regulated and its subcellular localization was aberrant in Δmobzip3, which leads to a disordered actin assembly in the Δmobzip3 appressorium. Taken together, these results revealed new regulatory functions of the bZIP transcription factor MoBZIP3, in regulating M. oryzae appressorium turgor formation and infection. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A comprehensive characterization of water stress is needed for the development of automated irrigation protocols aiming to increase olive orchard environmental and economical sustainability. The main aim of this study is to determine whether a combination of continuous leaf turgor, fruit growth, and sap flow responses improves the detection of mild water stress in two olive cultivars characterized by different responses to water stress. The sensitivity of the tested indicators to mild stress depended on the main mechanisms that each cultivar uses to cope with water deficit. One cultivar showed pronounced day to day changes in leaf turgor and fruit relative growth rate in response to water withholding. The other cultivar reduced daily sap flows and showed a pronounced tendency to reach very low values of leaf turgor. Based on these responses, the sensitivity of the selected indicators is discussed in relation to drought response mechanisms, such as stomatal closure, osmotic adjustment, and tissue elasticity. The analysis of the daily dynamics of the monitored parameters highlights the limitation of using non-continuous measurements in drought stress studies, suggesting that the time of the day when data is collected has a great influence on the results and consequent interpretations, particularly when different genotypes are compared. Overall, the results highlight the need to tailor plant-based water management protocols on genotype-specific physiological responses to water deficit and encourage the use of combinations of plant-based continuously monitoring sensors to establish a solid base for irrigation management. [ABSTRACT FROM AUTHOR]

Simple Summary: Measures of plant water status on kiwifruit were evaluated using Sentinel-2 (A/B) for two seasons in Central Chile. 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'Higgins region, Chile for season 2018–2019 and 2019–2020. 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's site, eleven sensors were installed in five trees, which continuously measured the leaf's turgor pressure (Yara Water-Sensor). A strong Spearman's (ρ) correlation between turgor pressure and vegetation indices was obtained, having −0.88 with EVI and −0.81 with GVMI for season 2018–2019, and lower correlation for season 2019–2020, reaching −0.65 with Rededge1 and −0.66 with EVI. However, the NIR range'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's water conditions and incorporate the sensitivity of different wavelengths. [ABSTRACT FROM AUTHOR]

Root hair elongation relies on polarized cell expansion at the growing tip. As a major osmotically active ion, potassium is expected to be continuously assimilated to maintain cell turgor during hair tip growth. However, due to the lack of practicable detection methods, the dynamics and physiological role of K+ in hair growth are still unclear. In this report, we apply the small-molecule fluorescent K+ sensor NK3 in Arabidopsis root hairs for the first time. By employing NK3, oscillating cytoplasmic K+ dynamics can be resolved at the tip of growing root hairs, similar to the growth oscillation pattern. Cross-correlation analysis indicates that K+ oscillation leads the growth oscillations by approximately 1.5 s. Artificially increasing cytoplasmic K+ level showed no significant influence on hair growth rate, but led to the formation of swelling structures at the tip, an increase of cytosolic Ca2+ level and microfilament depolymerization, implying the involvement of antagonistic regulatory factors (e.g., Ca2+ signaling) in the causality between cytoplasmic K+ and hair growth. These results suggest that, in each round of oscillating root hair elongation, the oscillatory cell expansion accelerates on the heels of cytosolic K+ increment, and decelerates with the activation of antagonistic regulators, thus forming a negative feedback loop which ensures the normal growth of root hairs. [ABSTRACT FROM AUTHOR]

Identifying the drought-tolerance traits of plant species originating from a moisture gradient will increase our understanding of the differences and similarities in plant drought tolerance. However, which traits can be used to evaluate drought tolerance remain an open question. Here, we conducted a common-garden experiment on 37 shrub species originating from desert to humid regions. The correlations between plant traits and the native environmental conditions were studied. Leaf sizes and Huber values were significantly correlated with most climate variables of the shrubs' origins. The osmotic potentials at full turgor (π100), turgor loss point (ΨTLP), and midday leaf water potential (Ψmid) were significantly correlated with most climate variables of their origins. We proposed using leaf sizes, Huber values, and ΨTLP as predictors of drought tolerance across shrub species and shrub biomes. Statistically significant correlations were found between π100, ΨTLP, and specific leaf area (SLA). However, owing to the weak correlations between SLA and the climate variables of the shrubs origins and between Huber values and leaf size and turgor loss traits, it was difficult to integrate leaf morphological traits with physiological traits to find a simple way to accurately quantify drought-tolerance-related differences among these shrub species. [ABSTRACT FROM AUTHOR]

Many halophytic physiological traits related to the tolerance of plants to salinity excess have been extensively studied, with a focus on biomass and/or gas exchange parameters. To gain a more complete understanding of whether salinity excess affects the physiological performance of halophytes, an experiment was performed using the halophyte Atriplex halimus L. as a model. A. halimus plants were subjected to two salinity treatments (171 and 513 mM NaCl) over 60 days in a controlled environment. After this period, dry biomass, specific stem conductivity, water potential at turgor loss point, osmotic potential, gas exchange parameters, and the fluorescence of chlorophyll a derived parameters were assessed in order to obtain knowledge about the differences in vulnerability that these parameters can show when subjected to salinity stress. Our results showed a decrease in belowground and aboveground biomass. The decrement in biomass seen at 513 mM NaCl was related to photosynthetic limitations and specific stem conductivity. Turgor loss point did not vary significantly with the increment of salinity. Therefore, the parameter that showed less vulnerability to saline stress was the turgor loss point, with only a 5% decrease, and the more vulnerable trait was the stem conductivity, with a reduction of nearly 50%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Leaf dehydration decreases water potential and cell turgor pressure. Therefore, changes in cell turgor pressure may regulate water transport across plant cell membranes. Using a cell pressure probe, the hydraulic properties of parenchyma cells in the midrib of maize (Zea mays L.) leaves were measured (half time T 1 / 2 of water exchange in cells as a measure of hydraulic conductivity Lp). Using intact plants with root systems encased in a pressure chamber, the root systems were pressurized and the turgor pressure in leaf cells increased by increments up to 0.3 MPa. However, the increase in the cell turgor did not increase but stabilized T 1 / 2 values. Increased water potential in leaf cells seemed to have stabilizing effects on the T 1 / 2 probably due to enhanced water availability. When the cell turgor decreased by 0.1 MPa to 0.3 MPa with releasing the pressure in the pressure chamber, T 1 / 2 was temporarily increased to a large degree, a factor of up to 13 within 30 min. [ABSTRACT FROM AUTHOR]