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Cortical lacunae caused by drought, especially observed in hybrids originating from Vitis rupestris, disrupt the connection between roots and soil. Yet, the physiological processes behind lacuna formation during drought and its consistency across Vitis species remain unclear. Here, we used a root pressure probe to investigate fine root hydraulic and mechanical properties, in the arid‐adapted R‐65 and drought‐susceptible 101‐14Mgt cultivars. We then performed P–V curves, root sap osmolality, and electrolyte leakage (EL) and used fluorescent light microscopy techniques. Only 101‐14Mgt showed lacunae formation during drought due to its stiffer cortical tissue, unlike R‐65. Lacunae resulted in a notable decline in root hydraulic conductivity during severe drought, with increased EL and root sap osmolality, indicating potential cellular damage. R‐65 displayed different and xerophyte‐like characteristics featuring a higher turgor loss point and decreased root capacitance, essential for maintaining root structural integrity in arid conditions. Our findings highlight lacuna formation is impacted by root tissue elasticity possibly linked to specific Vitis species favoring deeper rooting. In arid‐adapted grapevines, hydraulic regulators such as reduced turgor loss point, and root capacitance could contribute to enhanced drought tolerance. [ABSTRACT FROM AUTHOR]

Drought is one of the main factors contributing to tree mortality worldwide and drought events are set to become more frequent and intense in the face of a changing climate. Quantifying water stress of forests is crucial in predicting and understanding their vulnerability to drought‐induced mortality. Here, we explore the use of high‐resolution spectroscopy in predicting water stress indicators of two native Australian tree species, Callitris rhomboidea and Eucalyptus viminalis. Specific spectral features and indices derived from leaf‐level spectroscopy were assessed as potential proxies to predict leaf water potential (Ψleaf), equivalent water thickness (EWT) and fuel moisture content (FMC) in a dedicated laboratory experiment. New spectral indices were identified that enabled very high confidence linear prediction of Ψleaf for both species (R2 > 0.85) with predictive capacity increasing when accounting for a breakpoint in the relationships using segmented regression (E. viminalis, R2 > 0.89; C. rhomboidea, R2 > 0.87). EWT and FMC were also linearly predicted to a high accuracy (E. viminalis, R2 > 0.90; C. rhomboidea, R2 > 0.80). This study highlights the potential of spectroscopy as a tool for predicting measures of plant water noninvasively, enabling broader applications for monitoring and managing plant water stress. Summary Statement: This study explored the use of proximal spectroscopy in predicting plant water stress indicators of two native Australian tree species. We derived new spectral indices that enabled very high prediction of leaf water potential, equivalent water thickness, and fuel moisture content. [ABSTRACT FROM AUTHOR]

Hydraulic failure due to xylem embolism has been identified as one of the main mechanisms involved in drought‐induced forest decline. Trees vulnerability to hydraulic failure depends on their hydraulic safety margin (HSM). While it has been shown that HSM globally converges between tree species and biomes, there is still limited knowledge regarding how HSM can adjust locally to varying drought conditions within species. In this study, we relied on three long‐term partial rainfall exclusion experiments to investigate the plasticity of hydraulic traits and HSM for three Mediterranean tree species (Quercus ilex L., Quercus pubescens Willd., and Pinus halepensis Mill.). For all species, a homeostasis of HSM in response to rainfall reduction was found, achieved through different mechanisms. For Q. ilex, the convergence in HSM is attributed to the adjustment of both the turgor loss point (Ψtlp) and the water potential at which 50% of xylem conductivity is lost due to embolism (P50). In contrast, the maintenance of HSM for P. halepensis and Q. pubescens is related to its isohydric behavior for the first and leaf area adjustment for the latter. It remains to be seen whether this HSM homeostasis can be generalized and if it will be sufficient to withstand extreme droughts expected in the Mediterranean region. Summary statement: Mediterranean species submitted to aggravated water stress have maintained their hydraulic safety margin (HSM). For Pinus halepensis and Quercus pubescens, HSM maintenance resulted from their capacity to escape water stress, while it results from the plasticity of Ψtlp and P50 for Quercus ilex. [ABSTRACT FROM AUTHOR]

Quantifying drought tolerance in crops is critical for agriculture management under environmental change, and drought response traits in grape vine have long been the focus of viticultural research. Turgor loss point (πtlp) is gaining attention as an indicator of drought tolerance in plants, though estimating πtlp often requires the construction and analysis of pressure-volume (P-V) curves which are very time consuming. While P-V curves remain a valuable tool for assessing πtlp and related traits, there is considerable interest in developing high-throughput methods for rapidly estimating πtlp, especially in the context of crop screening. We tested the ability of a dewpoint hygrometer to quantify variation in πtlp across and within 12 clones of grape vine (Vitis vinifera subsp. vinifera) and one wild relative (Vitis riparia), and compared these results to those derived from P-V curves. At the leaf-level, methodology explained only 4–5% of the variation in πtlp while clone/species identity accounted for 39% of the variation, indicating that both methods are sensitive to detecting intraspecific πtlp variation in grape vine. Also at the leaf level, πtlp measured using a dewpoint hygrometer approximated πtlp values (r2 = 0.254) and conserved πtlp rankings from P-V curves (Spearman's ρ = 0.459). While the leaf-level datasets differed statistically from one another (paired t-test p = 0.01), average difference in πtlp for a given pair of leaves was small (0.1 ± 0.2 MPa (s.d.)). At the species/clone level, estimates of πtlp measured by the two methods were also statistically correlated (r2 = 0.304), did not deviate statistically from a 1:1 relationship, and conserved πtlp rankings across clones (Spearman's ρ = 0.692). The dewpoint hygrometer (taking ∼ 10–15 min on average per measurement) captures fine-scale intraspecific variation in πtlp, with results that approximate those from P-V curves (taking 2–3 h on average per measurement). The dewpoint hygrometer represents a viable method for rapidly estimating intraspecific variation in πtlp, and potentially greatly increasing replication when estimating this drought tolerance trait in grape vine and other crops. [ABSTRACT FROM AUTHOR]

ABSTRACT Plant hydraulic theory states that leaf and stem vulnerability to embolism is coordinated within individual plants. The hydraulic vulnerability segmentation hypothesis (HVSH) predicts higher vulnerability in leaves to protect the stem from hydraulic failure, preserving stem xylem, which is generally more metabolically expensive and slower to regenerate than leaf tissues. However, studies designed to test HVSH have reported wide ranges in vulnerability segmentation (VS), and patterns with the environment have been elusive. In this study, we tested HVSH in phylogenetically constrained tree species from contrasting ecosystems across the Australian landscape. In 12 species, we found no support for HVSH. While leaf vulnerability was strongly governed by climate, VS was universally absent or negative. Consistently, the onset of leaf embolism occurred after the loss of leaf turgor and seasonally low leaf water potentials, illustrating the rarity of embolism in leaves. Within the leaf, embolism primarily occurring first and last in the leaf midvein, suggesting redundancy in leaf architecture to preserve function. Overall, this multi‐ecosystem study provides a more complete picture of drought resistance mechanisms: (1) leaf safety was greatest in trees from drier ecosystems and (2) hydraulic thresholds were mostly conserved across organs indicating environmentally driven drought resistance in both leaves and stems. [ABSTRACT FROM AUTHOR]

The phytohormone abscisic acid (ABA) plays a major role in closing the stomata of angiosperms. However, recent reports of some angiosperm species having a peaking-type ABA dynamic, in which under extreme drought ABA levels decline to pre-stressed levels, raises the possibility that passive stomatal closure by leaf water status alone can occur in species from this lineage. To test this hypothesis, we conducted instantaneous rehydration experiments in the peaking-type species Umbellularia californica through a long-term drought, in which ABA levels declined to pre-stress levels, yet stomata remain closed. We found that when ABA levels were lowest during extreme drought, stomata reopen rapidly to maximum rates of gas exchange on instantaneous rehydration, suggesting that the stomata of U. californica were passively closed by leaf water status alone. This contrasts with leaves early in drought, in which ABA levels were highest and stomata did not reopen on instantaneous rehydration. The transition from ABA-driven stomatal closure to passively driven stomatal closure as drought progresses in this species occurs at very low water potentials facilitated by highly embolism-resistant xylem. These results have important implications for understanding stomatal control during drought in angiosperms. [ABSTRACT FROM AUTHOR]

In plants, sugars are the key source of energy and metabolic building blocks. The systemic transport of sugars is essential for plant growth and morphogenesis. Plants evolved intricate molecular networks to effectively distribute sugars. The dynamic distribution of these osmotically active compounds is a handy tool for regulating cell turgor pressure, an instructive force in developmental biology. In this study, we have investigated the molecular mechanism behind the dual role of the receptor-like kinase CANAR. We functionally characterized a long non-coding RNA, CARMA , as a negative regulator of CANAR. Sugar-responsive CARMA specifically fine-tunes CANAR expression in the phloem, the route of sugar transport. Our genetic, molecular, microscopy, and biophysical data suggest that the CARMA–CANAR module controls the shoot-to-root phloem transport of sugars, allows cells to flexibly adapt to the external osmolality by appropriate water uptake, and thus adjust the size of vascular cell types during organ growth and development. Our study identifies a nexus of plant vascular tissue formation with cell internal pressure monitoring, revealing a novel functional aspect of long non-coding RNAs in developmental biology. This study shows that the CARMA–CANAR module acts as a novel osmoregulatory system controlling cell size in the root stele in response to external osmolality. CANAR activity regulates the shoot-to-root phloem transport of sugars, which influences internal pressure via cellular water uptake and thus cell size. [ABSTRACT FROM AUTHOR]

Summary Drought predisposes forest trees to bark beetle‐induced mortality, but the physiological mechanisms remain unclear. While drought‐induced water and carbon limitations have been implicated in defensive failure and tree susceptibility, evidence demonstrating how these factors interact is scarce. We withheld water from mature, potted Pinus edulis and subsequently applied a double‐stem girdle to inhibit carbohydrate transport from the crown and roots. Within this isolated segment we then elicited a defense response by inoculating trees with a bark beetle‐fungal symbiont (Ophiostoma sp.). We quantified local mono‐ and sesquiterpenes (MST), nonstructural carbohydrates (NSC), and pressure potential of the inner bark. Both drought‐stressed and watered trees had similar NSC concentrations just before inoculation and depleted NSC similarly following inoculation, yet MST induction (i.e. increased concentration and altered composition) was constrained only in drought‐stressed trees. Thus, NSC consumption was largely unrelated to de novo MST synthesis. Instead, stoichiometric calculations show that induction originated largely from stored resin. Watered trees experiencing higher pressure potentials consistently induced higher MST concentrations. We demonstrate the importance of preformed resin toward an induced MST response in a semi‐arid conifer where drought‐constraints on defense occurred through biophysical limitations (i.e. reduced turgor hindering resin transport) rather than through substrate limitation. [ABSTRACT FROM AUTHOR]

If you ever forget to water your houseplant, you may find its leaves getting soft and droopy — if you water it again in time, the leaves may stiffen, spring back up, and resist gravity. During this recovery, plant cells absorb water and build up an intracellular pressure, called turgor pressure, similar to inflating a balloon. Turgor pressure is an intrinsic component of plant physiology, and its biomechanical role as the 'hydroskeleton' is generally appreciated either statically in structural stability, like leaves resisting gravity, or dynamically in rapid motions, like Venus flytrap snapping, Mimosa closing, or stomatal opening. Slow but non-static processes like plant cell expansion also rely on turgor pressure, and it has been increasingly realized that turgor pressure and water fluxes in plant tissues play active roles in plant growth and morphogenesis. But where does turgor pressure come from, and how does it interact with other biomechanical properties of a plant cell? This primer aims to answer these questions by taking a brief tour from osmosis, to pressure vessel theory, then plant cell rheology. Although this primer is centered around intracellular pressure in plant cells, the biomechanical concepts are generally applicable to other organisms like bacteria and fungi, and even animal cells, which do not have cell walls, but are either embedded in stiff extracellular matrix (ECM) or are contracting (see the following section). To explain some of these concepts, we included a few equations, most of which are not hard to derive at all. We encourage readers to check the included examples, try for themselves, and look up derivations in suggested further reading materials. Zhang et al. introduce intracellular pressure in plant cells and discuss how it affects and is affected by plant physiology. [ABSTRACT FROM AUTHOR]

ABSTRACT In ecophysiology leaves are frequently stored for hours after sampling before measuring their leaf water potential (Ψleaf). Here, we address a previously unidentified source of error, that metabolic heat generation can cause continuous water loss from leaves stored in impermeable bags, leading to a Ψleaf drop over time. We tested Ψleaf drop rates under various conditions: two bag materials, two species, initial Ψleaf above or below the turgor loss point (Ψtlp), and storage at 25°C versus 4°C. We partitioned leaf water loss due to condensation on the inner bag surface or permeation through the bag. We found that Ψleaf dropped by up to 0.39 MPa per hour, with 41%–89% of the water leaving the leaf condensed on the inner bag surface. Plastic bags showed higher Ψleaf drop rates than aluminium bags, and leaves above Ψtlp experienced greater drops. Storing leaves at 4°C reduced the Ψleaf drop rate by 60% compared to 25°C. Leaves were 0.2–0.3°C warmer than the bags, likely due to metabolic heating. Our energy balance model suggests that water loss is lower when storing leaves at cooler temperatures, using leaves with low stomatal conductance, deflated bags, and leaves with low Ψleaf. [ABSTRACT FROM AUTHOR]

Premise: Vascular epiphytes of tropical montane cloud forests are vulnerable to climate change, particularly as cloud bases elevate and reduce atmospheric inputs to the system. However, studies have generally focused on epiphytes in contiguous forests, with little research being done on epiphytes on isolated pasture trees. We investigated water relations of pasture‐tree epiphytes at three sites located below and above the elevation of the average cloud base in Monteverde, Costa Rica. Methods: We measured sap velocity and four microclimate variables in both the dry and wet season of 2018. We also measured functional traits, including pressure volume (PV) curves, predawn/midday water potential, and various lab‐based water relations traits. We used linear mixed models to assess the correlation between microclimate and sap velocity in both seasons and ANOVA to assess the variation in PV curve and water potential variables. Results: The turgor loss point generally increased from the wettest to driest site. However, this trend was driven primarily by the increasing prevalence of leaf succulence at drier sites. Microclimatic variables correlated strongly with sap velocity in the wet season, but low soil moisture availability caused this correlation to break down during the dry season. Conclusions: Our results emphasize the vulnerability of cloud forest epiphytes to rising cloud bases. This vulnerability may be more severe in pasture trees that lack the potential buffer of surrounding forest, but additional research that directly compares the canopy microclimate conditions between forest and pasture trees is needed to confirm this possibility. [ABSTRACT FROM AUTHOR]

ABSTRACT Determining the differences in flower hydraulic traits and structural resource allocation among closely related species adapted to low mean annual precipitation (MAP) can provide insight into plant adaptation to arid environments. Here, we measured the maximum flower hydraulic conductance (Kmax‐flower), water potential at induction 50% loss of Kmax‐flower (P50‐flower), flower pressure–volume parameters, dry mass of individual flowers and structural components (vexillum, wings, keels, stamens and sepals) of six Caragana species growing in regions ranging from 110 to 1400 mm MAP. Compared with species from high‐MAP environments, those from low‐MAP environments presented lower Kmax‐flower, more negative P50‐flower, osmotic potential at full turgor (πo) and turgor loss points (πtlp), and a greater bulk modulus of elasticity (ε). Consequently, a negative correlation between Kmax‐flower (hydraulic efficiency) and P50‐flower (hydraulic safety) was observed across Caragana species. Furthermore, the dry masses of individual flowers and structural components (vexillum, wings, keels, stamens and sepals) were greater in the species from the low‐MAP environment than in those from the high‐MAP environment. These findings suggest that greater flower hydraulic safety and drought tolerance combined with greater structural resource allocation promote drought adaptation in Caragana species to low‐MAP environments. [ABSTRACT FROM AUTHOR]

Pollination in Marantaceae is mediated by an explosive style movement. Before release, style tension is held by the hooded staminode. When a pollinator touches the trigger appendage of the hooded staminode the latter deforms and the style rapidly curls upwards. This movement has been interpreted as a turgor movement by some authors, but recent studies clearly indicate that setup, hold and release of tension are purely mechanical processes. However, in view of the high diversity of hooded staminodes, the question arises what keeps the tension in species with very thin staminodes. To test the holding mechanisms, we conducted mechanical and physico-chemical release experiments in four species with robust and four species with thin hooded staminodes in their natural tropical environment. We found almost the same response of all species to mechanical treatments, but species-specific reactions to different physico-chemical conditions. This indicates that style release follows the same mechanical principles in all species, but that the sensitivity of the explosive movement depends on material properties like tissue thickness and turgescence. As to the holding mechanisms, we found different degrees of floral synorganization. The hood of the hooded staminode formerly interpreted as an important holding structure does not play a noteworthy role. Instead, the basal plate of the hooded staminode antagonises the pressure of the style head against the holding point of the hooded staminode in species with robust hooded staminodes and well-developed basal plates. In some species with a thin hooded staminode, the latter is closely attached to the style and most likely stabilises tension by adhesive forces. In another species, a morphologically analogous structure adopts the function of the basal plate. We conclude that the holding mechanism of the style tension diversified during the evolution of Marantaceae whereas the release mechanism itself has been conserved throughout the family. [ABSTRACT FROM AUTHOR]

Postharvest assessment of 'Hass' avocado fruit ripening is frequently monitored by the fruit texture as it changes from hard to soft and 'buttery'. This large change in texture is easily measured, commonly by a penetrometer after removal of a small area of skin or by a whole-fruit compression measurement. The penetrometer is slow and destructive whereas the compression measurement is rapid and may be considered as non-destructive depending on the method. Investigation of the two methods on the same batch of fruit reveals information pertinent to the understanding of fruit ripening — beyond the simple provision of a numerical assessment of the progress of ripening. Monitoring of fruit under drying conditions revealed the role that fruit turgor plays in the compression measurement, and how it contributes to our understanding of the numerical values. Likewise, the observed variation among individual fruit ripening times may mean that averaged values are misleading, suggesting that fruit ripening takes longer than it actually does. The key element in the fruit-to-fruit variability was the pre-climacteric period before the fruit ripened. Additional penetrometer measurements of five regions of the fruit flesh for each fruit assessed quantified differences in mesocarp softening within the fruit. [ABSTRACT FROM AUTHOR]

The effect of individual sugars and pH of nutrient medium on growth and development of pollen tubes in an introgressive hybrid between common spruce and Siberian spruce (Picea abies (L.) Karst. × P. obovata Ledeb.) in vitro was investigated. Dynamics of growth of spruce pollen tubes was registered. It was found that relatively high growth rate of pollen tubes accounts for specific physiology of their development. A quick cellulose synthesis in the course of spruce pollen grains’ hydration was described. Differences in component composition of pollen and pollen tubes were revealed. Content of proteins, amino acids, RNA, DNA, lipids, and polysaccharides along the gradient of spruce pollen tubes abruptly increased towards the growing tip and became stabilized when they reached approximately half of their maximal length. At the same time, total content of carbohydrates in pollen tubes along their length essentially did not change. Formation on the surface of pollen tubes of outer rings consisting mainly of cellulose and callose are described. It was assumed that such rings may participate in regulation of turgor and partial compartmentation of protoplast in spruce pollen tubes. Callose present in pollen tubes should be regarded as a situational antistress polysaccharide that is not common component of tube wall. [ABSTRACT FROM AUTHOR]

Background and Aims Many agricultural areas are expected to face hotter, drier conditions from climate change. Understanding the mechanisms that crops use to mitigate these stresses can guide breeding for more tolerant plant material. We tested relationships between traits, physiological function in hot conditions and historical climate associations to evaluate these mechanisms for winegrapes. We expected a more negative leaf osmotic potential at full hydration (π o), which reduces leaf turgor loss during drought, and either a metabolically cheaper or more osmoprotectant leaf chemical composition, to allow cultivars associated with hot, dry regions to maintain greater gas exchange in hot growing conditions. Methods We measured π o, gas exchange and leaf chemistry for seven commercially important winegrape cultivars that vary widely in historical climate associations. Vines were grown in common-garden field conditions in a hot wine-growing region (Davis, CA, USA) and measured over the hottest period of the growing season (July–September). Key Results The value of π o varied significantly between cultivars, and all cultivars significantly reduced π o (osmotically adjusted) over the study period, although osmotic adjustment did not vary across cultivars. The value of π o was correlated with gas exchange and climate associations, but in the direction opposite to expected. Photosynthesis and π o were higher in the cultivars associated with hotter, less humid regions. Leaf chemical composition varied between cultivars but was not related to climate associations. Conclusions These findings suggest that maintenance of leaf turgor is not a primary limitation on grapevine adaptation to hot or atmospherically dry growing conditions. Thus, selecting for a more negative π o or greater osmotic adjustment is not a promising strategy to develop more climate-resilient grape varieties, contrary to findings for other crops. Future work is needed to identify the mechanisms increasing photosynthesis in the cultivars associated with hot, dry regions. [ABSTRACT FROM AUTHOR]

As climate change thrives, and the frequency of intense droughts is affecting many forested regions, a mechanistic understanding of the factors conferring drought tolerance in trees is increasingly important. However, studies linking the observed growth reduction to mechanistic traits are still rare. We compared the median growth anomalies of 16 native tree species, gathered across a network of study plots in Bavaria, with the mean species‐specific turgor loss point (πtlp) measured at five locations in Central Europe πtlp explained 37% of the growth anomalies observed in response to the intense droughts between 2018 and 2020 compared to the pre‐drought period between 2006 and 2017 across sites. πtlp constitutes an important leaf drought tolerance trait and influences the growth response of native tree species during extraordinary dry periods. As climate change‐induced droughts intensify, tree species with drought‐tolerant leaves will be less vulnerable to growth reductions. πtlp provides a useful indicator for selecting tree species to adapt forest management systems to climate change. [ABSTRACT FROM AUTHOR]

The African Restionaceae (Poales), the dominant graminoid layer in the megadiverse Cape Floristic Region of South Africa, are distributed across a wide range of moisture availability, yet currently there is very little known about the underlying hydraulics of this group.We tested two methods for measuring culm vulnerability to embolism, the optical and pneumatic methods, in three species of Cannomois ranging in habitat from semi‐riparian (Cannomois virgata) to dryland (Cannomois parviflora and C. congesta). Estimates of culm xylem vulnerability were coupled with measures of turgor loss point (ΨTLP) and minimum field water potential (ΨMD) to assess hydraulic safety margins.The optical and pneumatic methods produced similar estimates of P50, but differed for P12 and P88. All three species were quite vulnerable to embolism, with P50 of –1.9 MPa (C. virgata), −2.3 MPa (C. congesta), and −2.4 MPa (C. parviflora). Estimates of P50, ΨTLP and ΨMD aligned with habitat moisture stress, with highest values found in the semi‐riparian C. virgata. Consistent differences in P50, ΨMD and ΨTLP between species resulted in consistent hydraulic safety margins across species of 0.96 ± 0.1 MPa between ΨMD and P50, with onset of embolism occurring 0.43 ± 0.04 MPa after ΨTLP for all three species.Our study demonstrates that restio occupancy of dry environments involves more than the evolution of highly resistant xylem, suggesting that other aspects of water relations are key to understanding trait–environment relationships in this group. [ABSTRACT FROM AUTHOR]

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]

Being sessile, plants adapt to fluctuating environments and survive in their habitats; to accomplish this, plant cells have evolved their own physical properties by developing “cell wall” and “large vacuole”, the former of which provides the physical strength and protection, while the latter generates turgor pressure from within the cell, thereby acting as the driving force for cell expansion. In such unique physical environments within plant cells, material circulation is facilitated through the fast flow of the cytoplasm, namely “cytoplasmic streaming”. This review summarizes how these plant-specific facets are organized in plant cells with the aid of cytoskeletal elements. [ABSTRACT FROM AUTHOR]

Summary: Turgor loss point (TLP) is an important proxy for plant drought tolerance, species habitat suitability, and drought‐induced plant mortality risk. Thus, TLP serves as a critical tool for evaluating climate change impacts on plants, making it imperative to develop high‐throughput and in situ methods to measure TLP.We developed hyperspectral pressure–volume curves (PV curves) to estimate TLP using leaf spectral reflectance. We used partial least square regression models to estimate water potential (Ψ) and relative water content (RWC) for two species, Frangula caroliniana and Magnolia grandiflora. RWC and Ψ's model for each species had R2 ≥ 0.7 and %RMSE = 7–10. We constructed PV curves with model estimates and compared the accuracy of directly measured and spectra‐predicted TLP.Our findings indicate that leaf spectral measurements are an alternative method for estimating TLP. F. caroliniana TLP's values were −1.62 ± 0.15 (means ± SD) and −1.62 ± 0.34 MPa for observed and reflectance predicted, respectively (P > 0.05), while M. grandiflora were −1.78 ± 0.34 and −1.66 ± 0.41 MPa (P > 0.05).The estimation of TLP through leaf reflectance‐based PV curves opens a broad range of possibilities for future research aimed at understanding and monitoring plant water relations on a large scale with spectral ecophysiology. [ABSTRACT FROM AUTHOR]

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Direct and non-destructive measurements of plant-water relations of plants exhibiting the Crassulacean acid metabolism (CAM) photosynthetic pathway are seldom addressed, with most findings inferred from gas exchange measurements. The main focus of this paper was to study how the water exchange between the chlorenchyma and the hydrenchyma depends on and follows the CAM photosynthetic diel pattern using non-invasive and continuous methods. Gas exchange and leaf patch clamp pressure probe (LPCP) measurements were performed on Aloe vera (L.) Burm f., a CAM species, and compared to measurements on banana (Musa acuminata Colla), a C3 species. The LPCP output pressure, Pp, of Aloe vera plants follows its diel CAM photosynthetic cycle, reversed to that observed in banana and other C3 species. The four phases of CAM photosynthesis can also be identified in the diel LPCP output pressure, Pp, cycle. The Pp values in Aloe vera are determined by the hydrenchyma turgor pressure, with both parameters being reversely related. A non-invasive and continuous assessment of the water exchange between the chlorenchyma and the hydrenchyma in CAM plants, namely, by following the changes in the hydrenchyma turgor pressure, is presented. However, showing once more how the LPCP output pressure, Pp, depends on the leaf structure, such an approach can be used to study plant-water relations in other CAM species with a leaf structure similar to Aloe vera, with the hydrenchyma composing most of the leaf volume. [ABSTRACT FROM AUTHOR]

Drought is one of the most serious abiotic stresses to land plants. Plants sense and respond to drought stress to survive under water deficiency. Scientists have studied how plants sense drought stress, or osmotic stress caused by drought, ever since Charles Darwin, and gradually obtained clues about osmotic stress sensing and signaling in plants. Osmotic stress is a physical stimulus that triggers many physiological changes at the cellular level, including changes in turgor, cell wall stiffness and integrity, membrane tension, and cell fluid volume, and plants may sense some of these stimuli and trigger downstream responses. In this review, we emphasized water potential and movements in organisms, compared putative signal inputs in cell wall‐containing and cell wall‐free organisms, prospected how plants sense changes in turgor, membrane tension, and cell fluid volume under osmotic stress according to advances in plants, animals, yeasts, and bacteria, summarized multilevel biochemical and physiological signal outputs, such as plasma membrane nanodomain formation, membrane water permeability, root hydrotropism, root halotropism, Casparian strip and suberin lamellae, and finally proposed a hypothesis that osmotic stress responses are likely to be a cocktail of signaling mediated by multiple osmosensors. We also discussed the core scientific questions, provided perspective about the future directions in this field, and highlighted the importance of robust and smart root systems and efficient source‐sink allocations for generating future high‐yield stress‐resistant crops and plants. [ABSTRACT FROM AUTHOR]

As heatwave frequency increases, they are more likely to coincide with other disturbances like insect defoliation. But it is unclear if high temperatures after defoliation impact canopy recovery or leaf traits which may affect response to further stressors like drought. To examine these stressor interactions, we subjected defoliated (DEF) and undefoliated (UNDEF) oak saplings to a simulated spring heatwave of +10°C for 25 days. We measured gas exchange, leaf area recovery, carbohydrate storage, turgor loss point (ΨTLP), and minimum leaf conductance (gmin). During the heatwave, stem respiration exhibited stronger thermal acclimation in DEF than UNDEF saplings, while stomatal conductance and net photosynthesis increased. The heatwave did not affect leaf area recovery or carbohydrate storage of DEF saplings, but reflush leaves had higher gmin than UNDEF leaves, and this was amplified by the heatwave. Across all treatments, higher gmin was associated with higher daytime stomatal conductance and a lower ΨTLP. The results suggest defoliation stress may not be exacerbated by higher temperatures. However, reflush leaves are less conservative in their water use, limiting their ability to minimise water loss. While lower ΨTLP could help DEF trees maintain gas exchange under mild drought, they may be more vulnerable to dehydration under severe drought. Summary Statement: Leaf area recovery and carbohydrate storage after spring defoliation were not impacted by a coinciding heatwave. However, reflush leaves had higher minimum rates of water loss—and this effect was exacerbated by the heatwave, suggesting reduced drought tolerance. [ABSTRACT FROM AUTHOR]

Stomata are the key nodes linking photosynthesis and transpiration. By regulating the opening degree of stomata, plants successively achieve the balance between water loss and carbon dioxide acquisition. The dynamic behaviour of stomata is an important cornerstone of plant adaptability. Though there have been miscellaneous experimental results on stomata and their constituent cells, the guard cells and the subsidiary cells, current theory of stomata regulation is far from clear and unified. In this work, we develop an integrated model to describe the stomatal dynamics of seed plants based on existing experimental results. The model includes three parts: (1) a passive mechanical model of the stomatal aperture as a bivariate function of the guard‐cell turgor and the subsidiary‐cell turgor; (2) an active regulation model with a target ion‐content in guard cells as a function of their water potential; and (3) a dynamical model for the movement of potassium ions and water content. Our model has been used to reproduce abundant experimental phenomena semi‐quantitatively. With accurately measured parameters, our model can also be used to predict stomatal responses to changes of environmental conditions. Summary statement: A stomata model is developed based on existing experiments and reproduces important stomatal behaviour. The model takes into account passive mechanical interaction between guard cells and subsidiary cells, active movement of potassium ions, and water transport driven by water potential. [ABSTRACT FROM AUTHOR]

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.

Turgor is the driving force of plant growth, making it possible for roots to overcome soil resistance or for stems to counteract gravity. Maintaining a constant growth rate while avoiding cell content dilution, which would progressively stop the inward water flux, imposes the production or import of osmolytes in proportion to the increase of volume. We coin this phenomenon stationary osmoregulation. The article explores the quantitative consequences of this hypothesis on the interaction of a cylindrical cell growing axially against an obstacle. An instantaneous axial compression of a pressurized cylindrical cell generates a force and a pressure jump, which both decrease towards a lower value once water has flowed out of the cell to reach the water potential equilibrium. In the first part, the article derives analytical formulae for these forces and over-pressure both before and after relaxation. In the second part, we describe how the coupling of the Lockhart growth law with the stationary osmoregulation hypothesis predicts a transient slowdown in growth due to contact before a re-acceleration in growth. We finally compare these predictions with the output of an elastic growth model which ignores the osmotic origin of growth: models only match in the early phase of contact for a high-stiffness obstacle.

Xyloglucan is believed to play a significant role in cell wall mechanics of dicot plants. Surprisingly, Arabidopsis plants defective in xyloglucan biosynthesis exhibit nearly normal growth and development. We investigated a mutant line, cslc-Δ5 , lacking activity in all five Arabidopsis cellulose synthase like-C (CSLC) genes responsible for xyloglucan backbone biosynthesis. We observed that this xyloglucan-deficient line exhibited reduced cellulose crystallinity and increased pectin levels, suggesting the existence of feedback mechanisms that regulate wall composition to compensate for the absence of xyloglucan. These alterations in cell wall composition in the xyloglucan-absent plants were further linked to a decrease in cell wall elastic modulus and rupture stress, as observed through atomic force microscopy (AFM) and extensometer-based techniques. This raised questions about how plants with such modified cell wall properties can maintain normal growth. Our investigation revealed two key factors contributing to this phenomenon. First, measurements of turgor pressure, a primary driver of plant growth, revealed that cslc-Δ5 plants have reduced turgor, preventing the compromised walls from bursting while still allowing growth to occur. Second, we discovered the conservation of elastic asymmetry (ratio of axial to transverse wall elasticity) in the mutant, suggesting an additional mechanism contributing to the maintenance of normal growth. This novel feedback mechanism between cell wall composition and mechanical properties, coupled with turgor pressure regulation, plays a central role in the control of plant growth and is critical for seedling establishment in a mechanically challenging environment by affecting shoot emergence and root penetration. • Normal xyloglucan levels are important for seedling establishment • Changes in xyloglucan content affect turgor pressure • Reduced xyloglucan induces a reduction in cellulose crystallinity • Reduced xyloglucan leads to softer and weaker cell walls Bou Daher et al. show that Arabidopsis mutants lacking xyloglucan have reduced cellulose crystallinity, altered cell wall mechanical properties, and a reduction in turgor pressure. Bou Daher et al. also demonstrate the importance of xyloglucan in early seedling establishment. [ABSTRACT FROM AUTHOR]

• Leaf turgor pressure varied significantly in the azimuthal, vertical, and radial apple canopies under drip irrigation. • Water potential, leaf thickness, and solar radiation affected the variation in canopy leaf turgor. • MaxP p was optimal for soil moisture monitoring based on the XGBoost model. • The LPCP probe should be installed in the middle position of the east canopy's central layer for apple trees. Leaf turgor pressure is a relevant metric for determining plant water content. To diagnose an apple tree water shortage, it is critical to precisely establish the features of leaf turgor pressure change in the canopy. In the current study, we continually monitored the leaf turgor pressure parameter (P p) at different azimuthal, vertical, and radial locations of the apple canopy based on leaf patch clamp pressure (LPCP) probes. The results demonstrated that the P p curves on sunny and rainy days were significantly different. A peak occurred on sunny days, during which the turgor pressure remained constant around midday. Under full irrigation, there was a greater change rate and daily maximum of P p (maxP p) at the east (azimuthal), upper layer (vertical), and distal (radial) positions. While leaf turgor pressure dramatically decreased with incomplete watering, maxP p significantly increased at the central and lower layers of the east canopy, as well as on the proximal and middle of the radial parts. This spatial heterogeneity in canopy leaf turgor pressure was related to the soil water potential, midday leaf water potential, sponge tissue thickness, and canopy solar radiation. Then, the ideal drought stress indicator parameter (maxP p) and canopy turgor monitoring leaf location (the middle position of the eastern canopy central layer's radial branch) were determined by multiparameter assessment. The findings presented above serve as a theoretical foundation for the construction of an intelligent irrigation system based on apple tree water status monitoring. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "PECTATE LYASE LIKE12 patterns the guard cell wall to coordinate turgor pressure and wall mechanics for proper stomatal function in Arabidopsis" published in The Plant Cell journal. The correction addresses two typographical errors in the "Materials and methods" section related to the concentrations of fusicoccin and ABA used in the study. The correct concentrations should be listed as 1 μM and 50 μM, respectively, instead of 1 mM and 50 mM. The authors apologize for the error and have made the necessary corrections in this notice. [Extracted from the article]