• Plants grow and transpire during the night. The aim of the present work was to assess the relative flows of carbon, water and solutes, and the energy involved, in sustaining night-time ...transpiration and leaf expansive growth under control and salt-stress conditions.
• Published and unpublished data were used, for barley plants grown in presence of 0.5–1 mM NaCl (control) and 100 mM NaCl.
• Night-time leaf growth presents a more efficient use of taken-up water compared with day-time growth. This efficiency increases several-fold with salt stress. Night-time transpiration cannot be supported entirely through osmotically driven uptake of water through roots under salt stress. Using a simple three- (root medium/cytosol/vacuole) compartment approach, the energy required to support cell expansion during the night is in the lower percentage region (0.03–5.5%) of the energy available through respiration, under both, control and salt-stress conditions. Use of organic (e.g. hexose equivalents) rather than inorganic (e.g. Na⁺, Cl⁻, K⁺) solutes for generation of osmotic pressure in growing cells, increases the energy demand by orders of magnitude, yet requires only a small portion of carbon assimilated during the day.
• Night-time transpiration and leaf expansive growth should be considered as a potential acclimation mechanism to salinity.
The non-protein amino acid γ-aminobutyric acid (GABA) has been proposed to be an ancient messenger for cellular communication conserved across biological kingdoms. GABA has well-defined signalling ...roles in animals; however, whilst GABA accumulates in plants under stress it has not been determined if, how, where and when GABA acts as an endogenous plant signalling molecule. Here, we establish endogenous GABA as a bona fide plant signal, acting via a mechanism not found in animals. Using Arabidopsis thaliana, we show guard cell GABA production is necessary and sufficient to reduce stomatal opening and transpirational water loss, which improves water use efficiency and drought tolerance, via negative regulation of a stomatal guard cell tonoplast-localised anion transporter. We find GABA modulation of stomata occurs in multiple plants, including dicot and monocot crops. This study highlights a role for GABA metabolism in fine tuning physiology and opens alternative avenues for improving plant stress resilience.
•A link between water stress, cuticle properties and fruit firmness was investigated.•Water stress increased fruit cuticle load and thickness while reducing permeability.•Fruit transpiration rate and ...firmness loss are reduced by water limiting conditions.•Water stress affects cuticle properties along fruit growth but not after detachment.
While fleshy fruit softening has long been mechanistically linked to cell wall disassembly, the importance of the fruit cuticle in water relations and firmness has been suggested through studies of the long-shelf life delayed fruit deterioration (dfd) tomato genotype. We tested the hypothesis that dynamic cuticle properties and composition affect tomato fruit transpiration and firmness and are influenced by environmental water availability, using dfd and two normally softening fruit cultivars, Ailsa Craig (AC) and M82, grown under control and water stress (WS) conditions. The effect of WS was also assessed following fruit detachment. WS increased fruit firmness, cuticle load, and the expression of cuticle biosynthetic genes, while reducing cuticle permeability and fruit transpiration rate in AC and M82, but not in dfd fruit. This study supports a direct relationship between fruit cuticle properties, transpiration and firmness, and provides insights into the adaptation of tomato genotypes to environments where water can be scarce.
•The cooling effect of single and double transpiring surfaces of porous media at the leading edge of a wedge was studied.•The average cooling efficiency is best when the distance between the two ...discontinuous transpiration surfaces is 15 mm.•Discontinuous transpiration surface and variable porosity design can improve coolant flow distribution and cooling efficiency.
Transpiration cooling is an efficient thermal protection technology that can be applied to hypersonic aircraft. This paper takes the leading edge transpiration cooling system of aircraft as the research object, the full-field coupling numerical method is mainly used to study the cooling performance of the transpiration cooling system of the aircraft leading edge with a flight altitude of 20 km and a flight Mach number of 6. The correctness and accuracy of the numerical method and results are validated by comparison with experimental data in reference. The effects of 5 different types of coolant gases and injection rates on the cooling effectiveness of a transpiration cooling system with a single transpiration surface arrangement are first studied. The results show that helium gas with a larger specific heat capacity has better cooling performance. As the coolant injection rate increases, the average temperature of the solid wall decreases, but the coolant will be wasted. In order to improve the utilization rate of coolant and achieve system weight reduction and large area thermal protection, solve the problem of uneven surface temperature and high stagnation point temperature of the porous media, a discontinuous transpiration surface structure is designed, and the effectiveness of varying distances between the two transpiration surfaces and the combination of varying porosity on the cooling performance of the discontinuous transpiration surface structure are studied. The results show that an increase in the distance between transpiration surfaces can reduce the coolant flow rate at the stagnation point, leading to a slight increase in the temperature at the stagnation point and a decrease in cooling efficiency of about 10 %. At the same time, the temperature at the rear wall of the second transpiration surface decreases and the average efficiency is improved. When the variable porosity of the discontinuous transpiration surface is applied, the stagnation point temperature is reduced from 1218.17 K to 486.72 K, the cooling efficiency at the stagnation point is greatly improved, and the maximum reaches 0.874.
Increasing water scarcity challenges crop sustainability inmany regions. As a consequence, the enhancement of transpiration efficiency (TE)—that is, the biomass produced per unit of water ...transpired—has become crucial in breeding programs. This could be achieved by reducing plant transpiration through a better closure of the stomatal pores at the leaf surface. However, this strategy generally also lowers growth, as stomatal opening is necessary for the capture of atmospheric CO₂ that feeds daytime photosynthesis. Here, we considered the reduction in transpiration rate at night (En) as a possible strategy to limit water use without altering growth. For this purpose, we carried out a genetic analysis for En and TE in grapevine, a major crop in drought-prone areas. Using recently developed phenotyping facilities, potted plants of a cross between Syrah and Grenache cultivars were screened for 2 y under well-watered and moderate soil water deficit scenarios. High genetic variability was found for En under both scenarios and was primarily associated with residual diffusion through the stomata. Five quantitative trait loci (QTLs) were detected that underlay genetic variability in En. Interestingly, four of them colocalized with QTLs for TE. Moreover, genotypes with favorable alleles on these common QTLs exhibited reduced En without altered growth. These results demonstrate the interest of breeding grapevine for lower water loss at night and pave the way to breeding other crops with this underexploited trait for higher TE.
Stomata play a significant role in the Earth's water and carbon cycles, by regulating gaseous exchanges between the plant and the atmosphere. Under drought conditions, stomatal control of ...transpiration has long been thought to be closely coordinated with the decrease in hydraulic capacity (hydraulic failure due to xylem embolism). We tested this hypothesis by coupling a meta‐analysis of functional traits related to the stomatal response to drought and embolism resistance with simulations from a soil–plant hydraulic model. We report here a previously unreported phenomenon: the existence of an absolute limit by which stomata closure must occur to avoid rapid death in drought conditions. The water potential causing stomatal closure and the xylem pressure at the onset of embolism formation were equal for only a small number of species, and the difference between these two traits (i.e. safety margins) increased continuously with increasing embolism resistance. Our findings demonstrate the need to revise current views about the functional coordination between stomata and hydraulic traits and provide a mechanistic framework for modeling plant mortality under drought conditions.
The rapidly growing demand for humidity sensing in various applications such as noninvasive epidermal sensing, water status tracking of plants, and environmental monitoring has triggered the ...development of high-performance humidity sensors. In particular, timely communication with plants to understand their physiological status may facilitate preventing negative influence of environmental stress and enhancing agricultural output. In addition, precise humidity sensing at bio-interface requires the sensor to be both flexible and stable. However, challenges still exist for the realization of efficient and large-scale production of flexible humidity sensors for bio-interface applications. Here, a convenient, effective, and robust method for massive production of flexible and wearable humidity sensor is proposed, using laser direct writing technology to produce laser-induced graphene interdigital electrode (LIG-IDE). Compared to previous methods, this strategy abandons the complicated and costly procedures for traditional IDE preparation. Using graphene oxide (GO) as the humidity-sensitive material, a flexible capacitive-type GO-based humidity sensor with low hysteresis, high sensitivity (3215.25 pF/% RH), and long-term stability (variation less than ± 1%) is obtained. These superior properties enable the sensor with multifunctional applications such as noncontact humidity sensing and human breath monitoring. In addition, this flexible humidity sensor can be directly attached onto the plant leaves for real-time and long-term tracking transpiration from the stomata, without causing any damage to plants, making it a promising candidate for next-generation electronics for intelligent agriculture.
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•A convenient, effective, and robust method for massive production of flexible and wearable humidity sensor is developed based on laser-induced technology.•A flexible capacitive-type GO-based humidity sensor with low hysteresis, high sensitivity, and long-term stability is obtained.•The fabricated flexible and wearable sensor can be used for noncontact humidity sensing and human breath monitoring.•Real-time and long-term tracking of plant transpiration at bio-interface in realized without causing any physical damage to plants.
Stomatal responses to humidity, soil moisture and other factors that influence plant water status are critical drivers of photosynthesis, productivity, water yield, ecohydrology and climate forcing, ...yet we still lack a thorough mechanistic understanding of these responses. Here I review historical and recent advances in stomatal water relations. Clear evidence now implicates a metabolically mediated response to leaf water status (‘hydroactive feedback’) in stomatal responses to evaporative demand and soil drought, possibly involving abscisic acid production in leaves. Other hypothetical mechanisms involving vapor and heat transport within leaves may contribute to humidity, light and temperature responses, but require further theoretical clarification and experimental validation. Variation and dynamics in hydraulic conductance, particularly within leaves, may contribute to water status responses. Continuing research to fully resolve mechanisms of stomatal responses to water status should focus on several areas: validating and quantifying the mechanism of leaf-based hydroactive feedback, identifying where in leaves water status is actively sensed, clarifying the role of leaf vapor and energy transport in humidity and temperature responses, and verifying foundational but minimally replicated results of stomatal hydromechanics across species. Clarity on these matters promises to deliver modelers with a tractable and reliable mechanistic model of stomatal responses to water status.
•Maize, sorghum, and pearl millet had very contrasting species strategies to limit water losses.•Genetic variation for restricted transpiration rate found in all three species. Maize only saved water ...by restricting transpiration under high VPD.•Sorghum and pearl millet reduced leaf area when grown under high VPD, but not maize.•Maize had significantly higher TE than sorghum and millet under high VPD conditions.•Plant growth under high VPD altered the transient transpiration response to high VPD.
This study compared maize, sorghum and pearl-millet, leading C4 cereals, for the transpiration rate (TR) response to increasing atmospheric and soil water stress. The TR response to transiently increasing VPD (0.9–4.1 kPa) and the transpiration and leaf area expansion response to progressive soil drying were measured in controlled conditions at early vegetative stage in 10–16 genotypes of each species grown in moderate or high vapor pressure deficit (VPD) conditions. Maize grown under moderate VPD conditions restricted TR under high VPD, but not sorghum and pearl millet. By contrast, when grown under high VPD, all species increased TR upon increasing VPD, suggesting a loss of TR responsiveness. Sorghum and pearl-millet grown under high VPD reduced leaf area, but not maize. Upon progressive soil drying, maize reduced transpiration at higher soil moisture than sorghum and pearl millet, especially under high VPD, and leaf area expansion declined at similar or lower soil moisture than transpiration in maize and sorghum. It is concluded that maize conserves water by restricting transpiration upon increasing VPD and under higher soil moisture than sorghum and millet, giving maize significantly higher TE, whereas sorghum and pearl millet rely mostly on reduced leaf area and somewhat on transpiration restriction.
Because of intense transpiration and growth, the needs of plants for water can be immense. Yet water in the soil is most often heterogeneous if not scarce due to more and more frequent and intense ...drought episodes. The converse context, flooding, is often associated with marked oxygen deficiency and can also challenge the plant water status. Under our feet, roots achieve an incredible challenge to meet the water demand of the plant's aerial parts under such dramatically different environmental conditions. For this, they continuously explore the soil, building a highly complex, branched architecture. On shorter time scales, roots keep adjusting their water transport capacity (their so-called hydraulics) locally or globally. While the mechanisms that directly underlie root growth and development as well as tissue hydraulics are being uncovered, the signalling mechanisms that govern their local and systemic adjustments as a function of water availability remain largely unknown. A comprehensive understanding of root architecture and hydraulics as a whole (in other terms, root hydraulic architecture) is needed to apprehend the strategies used by plants to optimize water uptake and possibly improve crops regarding this crucial trait.
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