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Summary: Despite the importance of understanding plant growth, the mechanisms underlying how plant and fruit growth declines during drought remain poorly understood. Specifically, it remains unresolved whether carbon or water factors are responsible for limiting growth as drought progresses. We examine questions regarding the relative importance of water and carbon to fruit growth depending on the water deficit level and the fruit growth stage by measuring fruit diameter, leaf photosynthesis, and a proxy of cell turgor in olive (Olea europaea). Flow cytometry was also applied to determine the fruit cell division stage. We found that photosynthesis and turgor were related to fruit growth; specifically, the relative importance of photosynthesis was higher during periods of more intense cell division, while turgor had higher relative importance in periods where cell division comes close to ceasing and fruit growth is dependent mainly on cell expansion. This pattern was found regardless of the water deficit level, although turgor and growth ceased at more similar values of leaf water potential than photosynthesis. Cell division occurred even when fruit growth seemed to stop under water deficit conditions, which likely helped fruits to grow disproportionately when trees were hydrated again, compensating for periods with low turgor. As a result, the final fruit size was not severely penalized. We conclude that carbon and water processes are able to explain fruit growth, with importance placed on the combination of cell division and expansion. However, the major limitation to growth is turgor, which adds evidence to the sink limitation hypothesis. Significance Statement: The mechanism by which whole plants/organs reduce their growth during drought is still relatively little studied, the reduction of photosynthesis or turgor being the two major limitations considered. This paper aims at adding some evidence to the current debate on growth limitation thanks to a synchronous estimation of growth, turgor, and photosynthesis in olive trees (Olea europaea) exposed or not to water deficit using sensors and modeling with implications on process‐based models of forest and agriculture productivity. [ABSTRACT FROM AUTHOR]

Plant cell deformations are driven by cell pressurization and mechanical constraints imposed by the nanoscale architecture of the cell wall, but how these factors are controlled at the genetic and molecular levels to achieve different types of cell deformation is unclear. Here, we used stomatal guard cells to investigate the influences of wall mechanics and turgor pressure on cell deformation and demonstrate that the expression of the pectin-modifying gene PECTATE LYASE LIKE12 (PLL12) is required for normal stomatal dynamics in Arabidopsis thaliana. Using nanoindentation and finite element modeling to simultaneously measure wall modulus and turgor pressure, we found that both values undergo dynamic changes during induced stomatal opening and closure. PLL12 is required for guard cells to maintain normal wall modulus and turgor pressure during stomatal responses to light and to tune the levels of calcium crosslinked pectin in guard cell walls. Guard cell-specific knockdown of PLL12 caused defects in stomatal responses and reduced leaf growth, which were associated with lower cell proliferation but normal cell expansion. Together, these results force us to revise our view of how wall-modifying genes modulate wall mechanics and cell pressurization to accomplish the dynamic cellular deformations that underlie stomatal function and tissue growth in plants. [ABSTRACT FROM AUTHOR]

Global warming is exposing plants to increased risks of drought-driven mortality. Recent advances suggest that hydraulic failure is a key process leading to plant death, and the identification of simple and reliable proxies of species-specific risk of irreversible hydraulic damage is urgently required. We assessed the predictive power of leaf water content and shrinkage for monitoring leaf hydraulic failure in two Mediterranean native species, Salvia ceratophylloides (Sc) and S. officinalis (So). The study species showed significant differences in relative water content (RWC) thresholds inducing loss of rehydration capacity, as well as leaf hydraulic conductance (K L) impairment. Sc turned out to be more resistant to drought than So. However, Sc and So showed different leaf saturated water content values, so that different RWC values actually corresponded to similar absolute leaf water content. Our findings suggest that absolute leaf water content and leaf water potential, but not RWC, are reliable parameters for predicting the risk of leaf hydraulic impairment of two Salvia species, and their potential risk of irreversible damage under severe drought. Moreover, the lack of any K L decline until the turgor loss point in Sc , coupled to consistent leaf shrinkage, rejects the hypothesis to use leaf shrinkage as a proxy to predict K L vulnerability, at least in species with high leaf capacitance. Robust linear correlations between K L decline and electrolyte leakage measurements suggested a role of membrane damage in driving leaf hydraulic collapse. • Hydraulic failure is a major correlate of drought-driven plant death. • Simple parameters predicting the risk of irreversible hydraulic failure are needed. • Leaf hydraulic damage occurred at different RWC values in two Salvia species. • Absolute water content and cell membrane integrity predicted hydraulic failure. [ABSTRACT FROM AUTHOR]

Mechanical rupture, or lysis, of the cytoplasmic membrane is a common cell death pathway in bacteria occurring in response to β-lactam antibiotics. A better understanding of the cellular design principles governing the susceptibility and response of individual cells to lysis could indicate methods of potentiating β-lactam antibiotics and clarify relevant aspects of cellular physiology. Here, we take a single-cell approach to bacterial cell lysis to examine three cellular features—turgor pressure, mechanosensitive channels, and cell shape changes—that are expected to modulate lysis. We develop a mechanical model of bacterial cell lysis and experimentally analyze the dynamics of lysis in hundreds of single Escherichia coli cells. We find that turgor pressure is the only factor, of these three cellular features, which robustly modulates lysis. We show that mechanosensitive channels do not modulate lysis due to insufficiently fast solute outflow, and that cell shape changes result in more severe cellular lesions but do not influence the dynamics of lysis. These results inform a single-cell view of bacterial cell lysis and underscore approaches of combatting antibiotic tolerance to β-lactams aimed at targeting cellular turgor. [ABSTRACT FROM AUTHOR]

Phytophthora infestans , the most damaging oomycete pathogen of potato, is specialized to grow sporangiophore through opened stomata for secondary inoculum production. However, it is still unclear which metabolic pathways in potato are manipulated by P. infestans in the guard cell–pathogen interactions to open the stomata. Here microscopic observations and cell biology were used to investigate antagonistic interactions between guard cells and the oomycete pathogen. We observed that the antagonistic interactions started at the very beginning of infection. Stomatal movement is an important part of the immune response of potato to P. infestans infection and this occurs through guard cell death and stomatal closure. We observed that P. infestans appeared to manipulate metabolic processes in guard cells, such as triacylglycerol (TAG) breakdown, starch degradation, H2O2 scavenging, and NO catabolism, which are involved in stomatal movement, to evade these stomatal defense responses. The signal transduction pathway of P. infestans -induced stomatal opening likely starts from H2O2 and NO scavenging, along with TAG breakdown while the subsequent starch degradation reinforces the opening process by strengthening guard cell turgor and opening the stomata to their maximum aperture. These results suggest that stomata are a barrier stopping P. infestans from completing its life cycle, but this host defense system can be bypassed through the manipulation of diverse metabolic pathways that may be induced by P. infestans effector proteins. [ABSTRACT FROM AUTHOR]

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]

Over their lifetime, trees are repeatedly exposed to droughts. It is therefore important to understand whether repeated drought exposure makes trees more or less drought tolerant. Here, we investigated the effect of repeated droughts on functional trait expression and tree function in Eucalyptus obliqua. Further, we tested whether previous drought exposure enabled trees to avoid leaf death for longer under a subsequent severe drought. Trees were subjected for 1 year to 2 drought–rewatering cycles (drought treatment) or well-watered conditions, before imposing a severe drought. Trees in the drought treatment reduced their overall leaf area and biomass, whereas leaf-level anatomical, morphological and physiological traits remained mostly unaffected. There were no differences in water potential at the turgor loss point, leaf xylem vulnerability to embolism, leaf size, maximum xylem vessel diameter or cell wall thickness between treatments after the conditioning period. When exposed to a subsequent severe drought, trees previously exposed to drought were more drought tolerant due to a lower water potential at leaf death and tree-level morphological rather than physiological adjustments. Trees previously exposed to drought were smaller and used less water, which delayed leaf death for 39 days compared with 22 days for the well-watered trees. Our study indicates that previous drought exposure can facilitate tree-level morphological adjustment, which potentially enhances survival of E. obliqua trees during subsequent drought events. [ABSTRACT FROM AUTHOR]

As future climates continue to change, precipitation deficits are expected to become more severe across tropical ecosystems. As a result, it is important that we identify plant physiological traits that act as adaptations to drought, and determine whether these traits act synergistically or independently of each other. In this study, we assessed the role of three leaf-level putative adaptations to drought: crassulacean acid metabolism (CAM), the turgor loss point (TLPΨ) and water storage hydrenchyma tissue. Using the genus Clusia as a model, we were able to explore the extent to which these leaf physiological traits co-vary, and also how they contribute to species' distributions across a precipitation gradient in Central and South America. We found that CAM is independent of the TLPΨ and hydrenchyma depth in Clusia. In addition, we provide evidence that constitutive CAM is an adaptation to year-long water deficits, whereas facultative CAM appears to be more important for surviving acute dry seasons. Finally, we find that the other leaf traits tested did not correlate with environmental precipitation, suggesting that the reduced transpirational rates associated with CAM obviate the need to adapt the TLPΨ and hydrenchyma depth in this genus. By identifying physiological traits more common in drier environments, it is possible to understand the ways in which tropical trees have adapted to deal with drought. By analysing a genus from Central and South America, we were able to test if it is more beneficial to prevent or tolerate water loss. Our results show that preventing water loss has a greater benefit to living in drier niches, which has implications for the ways in which future climates will affect tropical flora. [ABSTRACT FROM AUTHOR]

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]

Summary: Photosynthetic sensitivity to drought is a fundamental constraint on land‐plant evolution and ecosystem function. However, little is known about how the sensitivity of photosynthesis to nonstomatal limitations varies among species in the context of phylogenetic relationships.Using saplings of 10 Eucalyptus species, we measured maximum CO2‐saturated photosynthesis using A–ci curves at several different leaf water potentials (ψleaf) to quantify mesophyll photosynthetic sensitivity to ψleaf (MPS), a measure of how rapidly nonstomatal limitations to carbon uptake increase with declining ψleaf. MPS was compared to the macroclimatic moisture availability of the species' native habitats, while accounting for phylogenetic relationships.We found that species native to mesic habitats have greater MPS but higher maximum photosynthetic rates during non‐water‐stressed conditions, revealing a trade‐off between maximum photosynthesis and drought sensitivity. Species with lower turgor loss points have lower MPS, indicating coordination among photosynthetic and water‐relations traits.By accounting for phylogenetic relationships among closely related species, we provide the first compelling evidence that MPS in Eucalyptus evolved in an adaptive fashion with climatically determined moisture availability, opening the way for further study of this poorly explored dimension of plant adaptation to drought. [ABSTRACT FROM AUTHOR]

Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi‐epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi‐epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (−63%), shorter stipe lengths (−56%), thicker laminae (+41%) and reduced stomatal density (−46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi‐epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi‐epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat. We detected key trait adaptions with xylem anatomy, frond structural traits and stomatal anatomy for avoidance of dehydration in both epiphytic and hemi‐epiphytic ferns species. Each of the trait adaptations we detected are clearly evident in phylogenetic trait reconstructions, suggesting that our findings provide a foundation on which to explain the evolution of epiphytism in ferns. [ABSTRACT FROM AUTHOR]

SUMMARY: Sexual reproduction in angiosperms is siphonogamous, and the interaction between pollen tube and pistil is critical for successful fertilization. Our previous study demonstrated that mutation of the Arabidopsis turgor regulation defect 1 (TOD1) gene leads to reduced male fertility, a result of retarded pollen tube growth in the pistil. TOD1 encodes a Golgi‐localized alkaline ceramidase, a key enzyme for the production of sphingosine‐1‐phosphate (S1P), which is involved in the regulation of turgor pressure in plant cells. However, whether TOD1s play a conserved role in the innovation of siphonogamy is largely unknown. In this study, we provide evidence that OsTOD1, which is similar to AtTOD1, is also preferentially expressed in rice pollen grains and pollen tubes. OsTOD1 knockout results in reduced pollen tube growth potential in rice pistil. Both the OsTOD1 genomic sequence with its own promoter and the coding sequence under the AtTOD1 promoter can partially rescue the attod1 mutant phenotype. Furthermore, TOD1s from other angiosperm species can partially rescue the attod1 mutant phenotype, while TOD1s from gymnosperm species are not able to complement the attod1 mutant phenotype. Our data suggest that TOD1 acts conservatively in angiosperms, and this opens up an opportunity to dissect the role of sphingolipids in pollen tube growth in angiosperms. [ABSTRACT FROM AUTHOR]

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

The cytoplasm of bacteria is maintained at a higher osmolality than the growth medium, which generates a turgor pressure. The cell membrane (CM) cannot support a large turgor, so there are two possibilities for transferring the pressure to the peptidoglycan cell wall (PGW): (1) the CM could be pressed directly against the PGW, or (2) the CM could be separated from the PGW by a periplasmic space that is isoosmotic with the cytoplasm. There is strong evidence for gram-negative bacteria that a periplasm exists and is isoosmotic with the cytoplasm. No comparable studies have been done for gram-positive bacteria. Here I suggest that a periplasmic space is probably essential in order for the periplasmic proteins to function, including especially the PBPs that remodel the peptidoglycan wall. I then present a semi-quantitative analysis of how teichoic acids could support a periplasm that is isoosmotic with the cytoplasm. The fixed anionic charge density of teichoic acids in the periplasm is ∼0.5 M, which would bring in ∼0.5 M Na+ neutralizing ions. This approximately balances the excess osmolality of the cytoplasm that would produce a turgor pressure of 19 atm. The 0.5 M fixed charge density is similar to that of proteoglycans in articular cartilage, suggesting a comparability ability to support pressure. An isoosmotic periplasm would be especially important for cell division, since it would allow CM constriction and PGW synthesis to avoid turgor pressure. [ABSTRACT FROM AUTHOR]

Stomata in leaves regulate gas exchange between the plant and its atmosphere. Various environmental stimuli elicit abscisic acid (ABA); ABA leads to phosphoactivation of slow anion channel 1 (SLAC1); SLAC1 activity reduces turgor pressure in aperture-defining guard cells; and stomatal closure ensues. We used electrophysiology for functional characterizations of Arabidopsis thaliana SLAC1 (AtSLAC1) and cryoelectron microscopy (cryo-EM) for structural analysis of Brachypodium distachyon SLAC1 (BdSLAC1), at 2.97-Å resolution. We identified 14 phosphorylation sites in AtSLAC1 and showed nearly 330-fold channel-activity enhancement with 4 to 6 of these phosphorylated. Seven SLAC1-conserved arginines are poised in BdSLAC1 for regulatory interaction with the N-terminal extension. This BdSLAC1 structure has its pores closed, in a basal state, spring loaded by phenylalanyl residues in high-energy conformations. SLAC1 phosphorylation fine-tunes an equilibrium between basal and activated SLAC1 trimers, thereby controlling the degree of stomatal opening. [ABSTRACT FROM AUTHOR]

The process of leaf elongation in grasses is characterized by the creation and transformation of distinct cell zones. The prevailing turgor pressure within these cells is one of the key drivers for the rate at which these cells divide, expand and differentiate, processes that are heavily impacted by drought stress. In this article, a turgor‐driven growth model for grass leaf elongation is presented, which combines mechanistic growth from the basis of turgor pressure with the ontogeny of the leaf. Drought‐induced reductions in leaf turgor pressure result in a simultaneous inhibition of both cell expansion and differentiation, lowering elongation rate but increasing elongation duration due to the slower transitioning of cells from the dividing and elongating zone to mature cells. Leaf elongation is, therefore, governed by the magnitude of, and time spent under, growth‐enabling turgor pressure, a metric which we introduce as turgor‐time. Turgor‐time is able to normalize growth patterns in terms of varying water availability, similar to how thermal time is used to do so under varying temperatures. Moreover, additional inclusion of temperature dependencies within our model pioneers a novel concept enabling the general expression of growth regardless of water availability or temperature. A model for grass leaf elongation is presented, which combines mechanistic growth based on turgor pressure and leaf ontogeny. An inverse relation was found between the rate and duration of the elongation rate, allowing for uniform expression of growth in terms of a new concept called 'turgor‐time'. [ABSTRACT FROM AUTHOR]

This study estimated the severity of Nilahue-Barahona and Las Máquinas wildfires, occurred in central Chile during the summer of 2016-17, by an empirical-statistical modelling based on pre- and post-fire arithmetic differences of spectral indices sensitive to vigor, turgor and calcination states of vegetation. By doing this, map of damages were created to aid the efficient management and ecological restoration of disturbed forestry ecosystems. The index differences were calculated from Sentinel-2 satellite images, acquired anually in the summers spanning from 2016 to 2019. The resulting nine index-derived differences were used as predictors of burn severity, field-measured during the summer of 2019 using the CBI (composite burn index) method, into a linear stepwise regression that allowed for selecting those with the highest predictability. CBI yielded low correlations as its calculation includes low vegetation strata largely recovered at the time of the field data collection. However, when overstory field data were used alone, correlations increased (70 % of the data = 0.80, P < 0.05). This was because this stratum was still appreciably damaged during the field campaign, along with its best representation from the image planimetry. The burn severity of both wildfires was mapped using the overstory data as regressand in a model based on NDWIex-ante-2019, NDWIex-ante-2018, NBRex-ante-2018 and NBRex-ante-2017 differences (R² ad = 0.77, RMSE = 0.35). [ABSTRACT FROM AUTHOR]

Summary: The effects of climate change on tropical forests will depend on how diverse tropical tree species respond to drought. Current distributions of evergreen and deciduous tree species across local and regional moisture gradients reflect their ability to tolerate drought stress, and might be explained by functional traits.We measured leaf water potential at turgor loss (i.e. 'wilting point'; πtlp), wood density (WD) and leaf mass per area (LMA) on 50 of the most abundant tree species in central Panama. We then tested their ability to explain distributions of evergreen and deciduous species within a 50 ha plot on Barro Colorado Island and across a 70 km rainfall gradient spanning the Isthmus of Panama.Among evergreen trees, species with lower πtlp were associated with drier habitats, with πtlp explaining 28% and 32% of habitat association on local and regional scales, respectively, greatly exceeding the predictive power of WD and LMA. In contrast, πtlp did not predict habitat associations among deciduous species.Across spatial scales, πtlp is a useful indicator of habitat preference for tropical tree species that retain their leaves during periods of water stress, and holds the potential to predict vegetation responses to climate change. [ABSTRACT FROM AUTHOR]

Summary: Under prolonged drought and reduced photosynthesis, plants consume stored nonstructural carbohydrates (NSCs). Stored NSC depletion may impair the regulation of plant water balance, but the underlying mechanisms are poorly understood, and whether such mechanisms are independent of plant water deficit is not known. If so, carbon costs of fungal symbionts could indirectly influence plant drought tolerance through stored NSC depletion.We connected well‐watered Pinus ponderosa seedling pairs via ectomycorrhizal (EM) networks where one seedling was shaded (D) and the other kept illuminated (LD) and compared responses to seedling pairs in full light (L). We measured plant NSCs, osmotic and water potential, and transfer of 13CO2 through EM to explore mechanisms linking stored NSCs to plant water balance regulation and identify potential tradeoffs between plant water retention and EM fungi under carbon‐limiting conditions.NSCs decreased from L to LD to D seedlings. Even without drought, NSC depletion impaired osmoregulation and turgor maintenance, both of which are critical for drought tolerance. Importantly, EM networks propagated NSC depletion and its negative effects on water retention from carbon stressed to nonstressed hosts.We demonstrate that NSC storage depletion influences turgor maintenance independently of plant water deficit and reveal carbon allocation tradeoffs between supporting fungal symbionts and retaining water. [ABSTRACT FROM AUTHOR]

Summary: Although xylem embolism resistance is traditionally considered as static, we hypothesized that in grapevine (Vitis vinifera) leaf xylem becomes more embolism‐resistant over the growing season.We evaluated xylem architecture, turgor loss point (ΨTLP) and water potentials leading to 25% of maximal stomatal conductance (gs25) or 50% embolism in the leaf xylem (P50) in three irrigation treatments and at three time points during the growing season, while separating the effects of leaf age and time of season.Hydraulic traits acclimated over the growing season in a coordinated manner. Without irrigation, ΨTLP, gs25, and P50 decreased between late May and late August by 0.95, 0.77 and 0.71 MPa, respectively. A seasonal shift in P50 occurred even in mature leaves, while irrigation had only a mild effect (< 0.2 MPa) on P50. Vessel size and pit membrane thickness were also seasonally dynamic, providing a plausible explanation for the shift in P50.Our findings provide clear evidence that grapevines can modify their hydraulic traits along a growing season to allow lower xylem water potential, without compromising gas exchange, leaf turgor or xylem integrity. Seasonal changes should be considered when modeling ecosystem vulnerability to drought or comparing datasets acquired at different phenological stages. [ABSTRACT FROM AUTHOR]

Summary: In the stems of terrestrial vascular plants studied to date, the diameter of xylem water‐conducting conduits D widens predictably with distance from the stem tip L approximating D ∝ Lb, with b ≈ 0.2. Because conduit diameter is central for conductance, it is essential to understand the cause of this remarkably pervasive pattern. We give reason to suspect that tip‐to‐base conduit widening is an adaptation, favored by natural selection because widening helps minimize the increase in hydraulic resistance that would otherwise occur as an individual stem grows longer and conductive path length increases. Evidence consistent with adaptation includes optimality models that predict the 0.2 exponent. The fact that this prediction can be made with a simple model of a single capillary, omitting much biological detail, itself makes numerous important predictions, e.g. that pit resistance must scale isometrically with conduit resistance. The idea that tip‐to‐base conduit widening has a nonadaptive cause, with temperature, drought, or turgor limiting the conduit diameters that plants are able to produce, is less consistent with the data than an adaptive explanation. We identify empirical priorities for testing the cause of tip‐to‐base conduit widening and underscore the need to study plant hydraulic systems leaf to root as integrated wholes. [ABSTRACT FROM AUTHOR]

An intimate interplay of the plasma membrane with curvature-sensing and curvature-inducing proteins would allow for defining specific sites or nanodomains of action at the plasma membrane, for example, for protrusion, invagination, and polarization. In addition, such connections are predestined to ensure spatial and temporal order and sequences. The combined forces of membrane shapers and the cortical actin cytoskeleton might hereby in particular be required to overcome the strong resistance against membrane rearrangements in case of high plasma membrane tension or cellular turgor. Interestingly, also the opposite might be necessary, the inhibition of both membrane shapers and cytoskeletal reinforcement structures to relieve membrane tension to protect cells from membrane damage and rupturing during mechanical stress. In this review article, we discuss recent conceptual advances enlightening the interplay of plasma membrane curvature and the cortical actin cytoskeleton during endocytosis, modulations of membrane tensions, and the shaping of entire cells. [ABSTRACT FROM AUTHOR]

Background: The research on plant salt tolerance has mainly focused on Na+, but Cl− has been relatively neglected. Previous studies have found that the xerophyte Pugionium cornutum, an important forage grass in the arid and semi‐arid regions of northwestern China, could synergistically accumulate high quintiles of Na+ and Cl− in its shoots under NaCl treatments. However, the separate effects of these ions on the adaptation of P. cornutum to saline conditions have not been investigated. Aims: In this study, the response of P. cornutum to Na+ and Cl− was analyzed. Methods: Four‐week‐old seedlings were treated with additional 50 mM NaCl, Na+‐specific solution containing 50 mM Na+ with a mix of NO3-, H2PO4-, and SO42- as counter anions, and Cl−‐specific solution containing 50 mM Cl− with a mix of K+, Ca2+, and Mg2+ as counter cations. Results: Compared with the normal growth condition irrigated with Hoagland solution, the Na+‐specific solution severely impaired the growth and photosynthesis of P. cornutum due to the high accumulation of Na+ in shoots and the deterioration of tissue K+ homeostasis; while the Cl−‐specific solution significantly increased shoot fresh and dry biomass. The Cl−‐specific solution could also increase the turgor pressure in leaves for enhancing osmotic adjustment, which should be mainly attributed to the large accumulation of Cl−, since the concentrations of other ions, including K+, Mg2+, Ca2+, H2PO4-, and SO42-, in tissues under Cl−‐specific treatment were maintained at the same levels as those observed under the normal condition. Conclusions: P. cornutum displays an excellent tolerance to moderate Cl− but not to Na+, and the large accumulation of Cl− should play a positive role in stimulating the growth of P. cornutum under salt stress. [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]

Summary: A valid representation of intra‐annual wood formation processes in global vegetation models is vital for assessing climate change impacts on the forest carbon stock. Yet, wood formation is generally modelled with photosynthesis, despite mounting evidence that cambial activity is rather directly constrained by limiting environmental factors.Here, we apply a state‐of‐the‐art turgor‐driven growth model to simulate 4 yr of hourly stem radial increment from Picea abies (L.) Karst. and Larix decidua Mill. growing along an elevational gradient. For the first time, wood formation observations were used to validate weekly to annual stem radial increment simulations, while environmental measurements were used to assess the climatic constraints on turgor‐driven growth.Model simulations matched the observed timing and dynamics of wood formation. Using the detailed model outputs, we identified a strict environmental regulation on stem growth (air temperature > 2°C and soil water potential > −0.6 MPa). Warmer and drier summers reduced the growth rate as a result of turgor limitation despite warmer temperatures being favourable for cambial activity.These findings suggest that turgor is a central driver of the forest carbon sink and should be considered in next‐generation vegetation models, particularly in the context of global warming and increasing frequency of droughts. [ABSTRACT FROM AUTHOR]

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

Design/methodology/approach: Two experiments were carried out; in the first it was evaluated the effect of five pulse solutions [(T1 = control (water); T2 = Hydraflor® 100 (0.5 g L-1); T3 = Hydraflor® 100 (0.5 g L-1) + sucrose (5% w/v); T4 = salicylic acid (1mM) and T5 = salicylic acid (1mM) + sucrose (5% w / v)] prior to storage at 11 ° C and 85 % RH for 10 d. In the second experiment, a wax coating was applied to the heliconia bracts and then maintain at 13 °C and 84% RH for 10 d; after storage the stems were placed in water or salicylic acid solution (1 mM). The results were analyzed by a completely randomized design, 10 replicates were used per treatment, one stem was one experimental unit. An ANOVA and a means comparison test (Tukey, α=0.05) were performed with the SAS version 9.4. Results: The anatomy of heliconia stems determines their vase life, since they have wide xylem vessels susceptible to cavitation, for which the absorption of water is limited, also and non-functional stomata in the bracts, which increase the loss of moisture from the tissue. The use of pulse solutions or preservatives has little effect in prolonging the life of heliconia stems. Therefore, the application of wax creates a physical barrier that maintains the turgor of the stems, reduces oxidation, maintaining the bracts quality and increased the total postharvest life for 6 d more than the control stems. Study Limitations/Implications: No limitations were found in this study. Findings/conclusions: The postharvest life of heliconia is conditioned by the loss of turgor and low water absorption, which leads to an early wilting of the inflorescences. The application of pulse solutions or preservatives have little effect in prolonging the life of the vase, so the most suitable technique to preserve the quality of the stems is waxing. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Oil Crop Sciences is the property of Oil Crops Research Institute of Chinese Academy of Agricultural Sciences 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.)

Background and Aims Turgor pressure within a plant cell represents the key to the mechanistical descriptiion of plant growth, combining the effects of both water and carbon availability. The high level of spatio-temporal variation and diurnal dynamics in turgor pressure within a single plant make it a challenge to model these on the fine spatial scale required for functional–structural plant models (FSPMs). A conceptual model for turgor-driven growth in FSPMs has been established previously, but its practical use has not yet been explored. Methods A turgor-driven growth model was incorporated in a newly established FSPM for soybean. The FSPM simulates dynamics in photosynthesis, transpiration and turgor pressure in direct relation to plant growth. Comparisons of simulations with field data were used to evaluate the potential and shortcomings of the modelling approach. Key Results Model simulations revealed the need to include an initial seed carbon contribution, a more realistic sink function, an estimation of respiration, and the distinction between osmotic and structural sugars, in order to achieve a realistic model of plant growth. However, differences between simulations and observations remained in individual organ growth patterns and under different environmental conditions. This exposed the need to further investigate the assumptions of developmental and environmental (in)sensitivity of the parameters, which represent physiological and biophysical organ properties in the model, in future research. Conclusions The model in its current form is primarily a diagnostic tool, to better understand and model the behaviour of water relations on the scale of individual plant organs throughout the plant life cycle. Potential future applications include its use as a phenotyping tool to capture differences in plant performance between genotypes and growing environments in terms of specific plant characteristics. Additionally, focused experiments can be used to further improve the model mechanisms to lead to better predictive FSPMs, including scenarios of water deficit. [ABSTRACT FROM AUTHOR]

Summary: Plants in nature are constantly exposed to organisms that touch them and wound them. A highly conserved response to these stimuli is a rapid collapse of membrane potential (i.e. a decrease of electrical field strength across membranes). This can be coupled to the production and/or action of jasmonate or ethylene. Here, the various types of electrical signals in plants are discussed in the context of hormone responses. Genetic approaches are revealing genes involved in wound‐induced electrical signalling. These include clade 3 GLUTAMATE RECEPTOR‐LIKE (GLR) genes, Arabidopsis H+‐ATPases (AHAs), RESPIRATORY BURST OXIDASE HOMOLOGUEs (RBOHs), and genes that determine cell wall properties. We briefly review touch‐ and wound‐induced increases in cytosolic Ca2+ concentrations and their temporal relationship to electrical activities. We then look at the questions that need addressing to link mechanostimulation and wound‐induced electrical activity to hormone responses. Utilizing recently published results, we also present a hypothesis for wound‐response leaf‐to‐leaf electrical signalling. This model is based on rapid electro‐osmotic coupling between the phloem and xylem. The model suggests that the depolarization of membranes within the vascular matrix triggered by physical stimuli and/or chemical elicitors is linked to changes in phloem turgor and that this plays vital roles in leaf‐to‐leaf electrical signal propagation. [ABSTRACT FROM AUTHOR]

How the plant cell wall expands and forms shapes is a long-standing mystery. Traditional thought is that turgor pressure drives these processes. However, a recent study by Haas and colleagues shows for the first time that the expansion of pectin homogalacturonan nanofilaments drives morphogenesis without turgor pressure in plant epidermal cells. [ABSTRACT FROM AUTHOR]

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

Turgor loss point (πtlp) has been suggested to be a key trait for drought resistance in woody species. In herbaceous grassland species, the role of πtlp for species drought survival has not yet been tested, although grasslands are projected to experience more frequent and intense droughts with climate change.To gain insights into the role of πtlp for drought resistance of temperate perennial grassland species, we assessed πtlp of 41 species common in Germany (20 forbs, 21 grasses). We directly related them to the species' comparative whole‐plant drought survival and midday leaf water potentials under drought (ΨMD) assessed in a common garden drought experiment, and to species moisture association.Species drought survival increased with increasing πtlp across all species as well as within forbs or grasses separately. ΨMD was positively related to πtlp and drought survival. Our results imply that high πtlp promotes drought survival of common perennial European temperate mesic grassland species by enabling them to maintain high leaf water potentials under drought, that is, a desiccation avoidance strategy. However, πtlp was not related to species moisture association.The positive relationship between πtlp and drought survival in herbaceous grassland species was opposite to the negative relationship previously established in woody plants, implying that mechanisms of drought resistance differ between woody and herbaceous species. Our results highlight the necessity of directly testing the relationship of functional traits to whole‐plant drought survival in different plant life forms, before using trait assessments for predicting plant responses to drought. A free plain language summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Identifying the drivers of stomatal closure and leaf damage during stress in grasses is a critical prerequisite for understanding crop resilience. Here, we investigated whether changes in stomatal conductance (gs) during dehydration were associated with changes in leaf hydraulic conductance (Kleaf), xylem cavitation, xylem collapse, and leaf cell turgor in wheat (Triticum aestivum). During soil dehydration, the decline of gs was concomitant with declining Kleaf under mild water stress. This early decline of leaf hydraulic conductance was not driven by cavitation, as the first cavitation events in leaf and stem were detected well after Kleaf had declined. Xylem vessel deformation could only account for <5% of the observed decline in leaf hydraulic conductance during dehydration. Thus, we concluded that changes in the hydraulic conductance of tissues outside the xylem were responsible for the majority of Kleaf decline during leaf dehydration in wheat. However, the contribution of leaf resistance to whole plant resistance was less than other tissues (<35% of whole plant resistance), and this proportion remained constant as plants dehydrated, indicating that Kleaf decline during water stress was not a major driver of stomatal closure. Decline in leaf hydraulic conductance under mild water stress is associated with outside‐xylem processes but does not drive stomatal closure in wheat. [ABSTRACT FROM AUTHOR]

Summary: The best predictor of leaf level photosynthetic rate is the porosity of the leaf surface, as determined by the number and aperture of stomata on the leaf. This remarkable correlation between stomatal porosity (or diffusive conductance to water vapour gs) and CO2 assimilation rate (A) applies to all major lineages of vascular plants (Figure 1) and is sufficiently predictable that it provides the basis for the model most widely used to predict water and CO2 fluxes from leaves and canopies. Yet the Ball–Berry formulation is only a phenomenological approximation that captures the emergent character of stomatal behaviour. Progressing to a more mechanistic prediction of plant gas exchange is challenging because of the diversity of biological components regulating stomatal action. These processes are the product of more than 400 million years of co‐evolution between stomatal, vascular and photosynthetic tissues. Both molecular and structural components link the abiotic world of the whole plant with the turgor pressure of the epidermis and guard cells, which ultimately determine stomatal pore size and porosity to water and CO2 exchange (New Phytol., 168, 2005, 275). In this review we seek to simplify stomatal behaviour by using an evolutionary perspective to understand the principal selective pressures involved in stomatal evolution, thus identifying the primary regulators of stomatal aperture. We start by considering the adaptive process that has locked together the regulation of water and carbon fluxes in vascular plants, finally examining specific evidence for evolution in the proteins responsible for regulating guard cell turgor. Significance Statement: Stomata regulate photosynthesis and transpiration in most extant plant species. The evolution of these critical valves provides an important insight into understanding land plant physiology. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated that the physical properties of intracellular bacterial gas vesicles (GVs) can be analyzed in vivo using pressure nephelometry. In analyzing the buoyant state of GV-containing cyanobacteria, hydrostatic pressure within a sample cell is increased in a stepwise manner, where the concomitant collapse of GVs due to pressure and the resultant decrease in suspended cells are detected by changes in nephelometric scattering. As the relative pressure at which GVs collapse is a function of turgor pressure and cellular osmotic gradients, pressure nephelometry is a powerful tool for assaying changes in metabolism that affect turgor, such as photosynthetic and osmoregulatory processes. We have developed an updated and automated pressure nephelometer that utilizes visible-infrared (Vis-IR) spectra to accurately quantify GV critical collapse pressure, critical collapse pressure distribution, and cell turgor pressure. Here, using the updated pressure nephelometer and axenic cultures of Microcystis aeruginosa PCC7806, we demonstrate that GV critical collapse pressure is stable during mid-exponential growth phase, introduce pressure-sensitive turbidity as a robust metric for the abundance of gas-vacuolate cyanobacteria, and demonstrate that pressure-sensitive turbidity is a more accurate proxy for abundance and growth than photopigment fluorescence. As cyanobacterium-dominated harmful algal bloom (cyano- HAB) formation is dependent on the constituent cells possessing gas vesicles, characterization of environmental cyanobacteria populations via pressure nephelometry is identified as an underutilized monitoring method. Applications of this instrument focus on physiological and ecological studies of cyanobacteria, for example, cyanoHAB dynamics and the drivers associated with cyanotoxin production in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales is the property of Academia Colombiana de Ciencias Exactas, Fisicas y Naturales 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.)

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]

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., (© 2024 Institute of Botany, Chinese Academy of Sciences.)

Peptidoglycan, which is the main component of the bacterial cell wall, is a heterogeneous polymer of glycan strands cross-linked with short peptides and is synthesized in cooperation with the cell division cycle. Although it plays a critical role in bacterial survival, its architecture is not well understood. Herein, we visualized the architecture of the peptidoglycan surface in Bacillus subtilis at the nanometer resolution, using quick-freeze, deep-etch electron microscopy (EM). Filamentous structures were observed on the entire surface of the cell, where filaments about 11 nm wide formed concentric circles on cell poles, filaments about 13 nm wide formed a circumferential mesh-like structure on the cylindrical part and a 'piecrust' structure was observed at the boundary. When growing cells were treated with lysozyme, the entire cell mass migrated to one side and came out from the cell envelope. Fluorescence labeling showed that lysozyme preferentially bound to a cell pole and cell division site, where the peptidoglycan synthesis was not complete. Ruffling of surface structures was observed during EM. When cells were treated with penicillin, the cell mass came out from a cleft around the cell division site. Outward curvature of the protoplast at the cleft seen using EM suggested that turgor pressure was applied as the peptidoglycan was not damaged at other positions. When muropeptides were depleted, surface filaments were lost while the rod shape of the cell was maintained. These changes can be explained on the basis of the working points of the chemical structure of peptidoglycan. [ABSTRACT FROM AUTHOR]

Summary: Signal coordination in response to changes in water availability remains unclear, as does the role of embolism events in signaling drought stress.Sunflowers were exposed to two drought treatments of varying intensity while simultaneously monitoring changes in stomatal conductance, acoustic emissions (AE), turgor pressure, surface‐level electrical potential, organ‐level water potential and leaf abscisic acid (ABA) concentration. Leaf, stem and root xylem vulnerability to embolism were measured with the single vessel injection technique.In both drought treatments, it was found that AE events and turgor changes preceded the onset of stomatal closure, whereas electrical surface potentials shifted concurrently with stomatal closure. Leaf‐level ABA concentration did not change until after stomata were closed. Roots and petioles were equally vulnerable to drought stress based on the single vessel injection technique. However, anatomical analysis of the xylem indicated that the increased AE events were not a result of xylem embolism formation. Additionally, roots and stems never reached a xylem pressure threshold that would initiate runaway embolism throughout the entire experiment.It is concluded that stomatal closure was not embolism‐driven, but, rather, that onset of stomatal closure was most closely correlated with the hydraulic signal from changes in leaf turgor. [ABSTRACT FROM AUTHOR]

• Leaf turgor pressure changes to D changes relate to maximum stomatal conductance. • We derived a physiological-based indicator from a leaf turgor pressure-related sensor. • g s,max can be automatically estimated from this indicator previous calibration. • We demonstrated this for three seasons in a commercial olive hedgerow orchard. • Results apply for moderate water stress levels within stomatal functioning ranges. Effective study and management of crops and forests would benefit greatly from useful plant-based indicators of the biological controls on evapotranspiration, and particularly stomatal conductance (g s). Given the strong influence of g s on bulk leaf water potential and turgor pressure (P), in vivo measurement of P may provide useful information about diurnal or seasonal dynamics of g s. Moderate plant water stress affects the diurnal dynamics of P as leaf-to-air vapour pressure deficit (D) varies, and these dynamics correlate to g s. Here, we explored relative changes in P in response to changes in D under mild drought conditions, and how these changes are linked to stomatal behaviour, and specifically to diurnal maximum g s (g s,max), one of the best indicators of plant water stress. We monitored ecophysiological and environmental variables, as well as a relative proxy for P , during three consecutive seasons in a hedgerow olive orchard where trees were supplied with different irrigation treatments to create well-watered and moderately water-stressed conditions. Our results demonstrated that the sensitivity of P to D correlated well with g s,max reached by the trees within a range in which variations in g s are the main diffusional limitation to photosynthesis. We further showed that this correlation held under a wide range of meteorological conditions and soil water availability. This turgor proxy measurement, which is much easier to measure than g s , can facilitate the use of g s,max as an indicator of plant water stress and evapotranspiration in agriculture and plant science research. [ABSTRACT FROM AUTHOR]

Summary: Maintaining water balance has been a critical constraint shaping the evolution of leaf form and function. However, flowers, which are heterotrophic and relatively short‐lived, may not be constrained by the same physiological and developmental factors.We measured physiological parameters derived from pressure–volume curves for leaves and flowers of 22 species to characterize the diversity of hydraulic traits in flowers and to determine whether flowers are governed by the same constraints as leaves.Compared with leaves, flowers had high saturated water content, which was a strong predictor of hydraulic capacitance in both leaves and flowers. Principal component analysis revealed that flowers occupied a different region of multivariate trait space than leaves and that hydraulic traits are more diverse in flowers than in leaves.Without needing to maintain high rates of transpiration, flowers rely on other hydraulic traits, such as high hydraulic capacitance, to maintain turgor pressure. As a result, instead of employing a metabolically expensive but durable carbon (C)‐based skeleton, flowers may rely predominantly on a metabolically cheaper, hydrostatic skeleton to keep their structures on display for pollinators, which has important implications for both the costs of reproduction and the biomechanical performance of flowers, particularly during drought. See also the Commentary on this article by Olson & Pittermann, 223: 8–10. [ABSTRACT FROM AUTHOR]

In arid and semi-arid areas, farmers are experiencing unprecedented water scarcity, which is likely to increase by the perspective of global warming. The purpose of this study was to evaluate the effect of three irrigation frequencies on vegetative growth, leaf turgor pressure, and photosynthesis of young olive trees (Olea europaea L. cvs 'Koroneiki' and 'Picholine'). We found that throughout the experiment and for all irrigation treatments, Picholine cultivar showed a higher rate of vegetative growth. In addition, the leaf turgor pressure for this cultivar showed fewer signs of stress overall as it recorded less Pp curve inversions during summer. However, during this season the photochemical efficiency in Picholine for the frequencies T1 and T2 were lower than Koroneiki by 9.53% and 10.63%, respectively. Which implied that the non-stomatal limitation of photosynthesis has an impact on Picholine photosynthetic production, which in turn indicates that this cultivar is more sensitive to high temperature. Moreover, irrigation frequency has little effect on the Koroneiki cultivar. [ABSTRACT FROM AUTHOR]

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