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Leaf area to sapwood area ratio (AL/AS) influences carbon sequestration, community composition, and ecosystem functioning in terrestrial vegetation and is closely related to leaf economics and hydraulics. However, critical predictors of AL/AS are not well understood. We compiled an AL/AS data set with 1612 species‐site combinations (1137 species from 285 sites worldwide) from our field experiments and published literature. We found the global mean AL/AS to be 0.63 m2 cm−2, with its variation largely driven by growing‐season precipitation (Pgs), which accounted for 18% of the variation in AL/AS. Species in tropical rainforests exhibited the highest AL/AS (0.82 m2 cm−2), whereas desert species showed the lowest AL/AS (0.16 m2 cm−2). Soil factors such as soil nitrogen and soil organic carbon exhibited positive effects on AL/AS, whereas soil pH was negatively correlated with AL/AS. Tree density accounted for 7% of the variation in AL/AS. All biotic and abiotic predictors collectively explained up to 45% of the variation in AL/AS. Additionally, AL/AS was positively correlated to the net primary productivity (NPP) of the ecosystem. Our study provides insights into the driving factors of AL/AS at the global scale and highlights the importance of AL/AS in ecosystem productivity. Given that Pgs is the most critical driver of AL/AS, alterations in global precipitation belts, particularly seasonal precipitation, may induce changes in plant leaf area on the branches. Summary statement: In this study, we assessed global patterns and key predictors of leaf area to sapwood area ratio (AL/AS) and underscored the significance of growing‐season precipitation, soil pH, and tree density in influencing AL/AS variation and its impact on plant primary productivity. [ABSTRACT FROM AUTHOR]

In this study, the effects of repeated cycles of drying and rehydration on some physiological traits were assessed in long shelf-life tomatoes cultivated in a typical semi-arid area of Southern Italy. Three Sicilian landraces ('Custonaci', 'Salina', and 'Vulcano') from the germplasm collection at CNR-IBE (Catania, Italy) and a commercial tomato mini-plum ('Faino Hy., control) were investigated under three water regimes: DRY (no irrigation), IRR (long-season full irrigation) and REW (post-drought rewaterings). Net photosynthetic assimilation rate (Pn), leaf transpiration (E), stomatal conductance (gs), instantaneous water use efficiency (WUEi), leaf intercellular CO2 (Ci, ppm), and leaf temperature (°C), were measured during the growing season. At harvest (late July), fruit production per plant was measured and ripened fruits were analysed for total solids (TS), soluble solids (SS), reducing sugars (RS), vitamin C (AscA), and total phenols (TP). Pn promptly responded to rewatering (REW), quickly increasing immediately after irrigation, and declined with soil drying up. All genotypes had similar physiological pathways in DRY, but in IRR, 'Faino' had higher Pn (up to 31 μmol CO2 m−2s−1) and E (up to 18 mmol H2O m−2s−1). Stomatal conductance (gs) after rewatering steeply increased and quickly declined after that. All local landraces had the same gs in IRR and REW. Variations in RWC were less pronounced than those in other physiological parameters. WUEi in REW and DRY proceeded similarly (up to 3 μmol CO2 mmol H2O). Irrigation in REW significantly promoted plant productivity over the DRY control (up to +150% in 'Vulcano'). TS and SS in REW were lower than those in DRY, but higher (+19 and +7%, respectively) than in IRR. Vitamin C was greater in DRY and REW (26 and 18% higher than in IRR, respectively). TP in all local tomatoes were significantly higher (up to +29% in 'Vulcano') than those in the commercial control. Water regime had a minor effect on TP in 'Custonaci' and 'Salina'. Principal Component Analysis (PCA) provided information on the changes in physiological and fruit quality traits in tomatoes in relation to cultivars and water regimes. The results of this study also revealed that a water-saving irrigation strategy where few irrigations are applied after prolonged periods of drought might be profitable in terms of fruit production enhancement in long shelf-life tomatoes and that limited rewaterings in most cases, help retaining high levels of fruit quality traits. [ABSTRACT FROM AUTHOR]

Wheat landraces are traditional varieties that have evolved over generations in response to local environments and farming practices and therefore exhibit remarkable adaptability to challenging climatic conditions and low-input farming systems. While the suitability of Mediterranean landraces to non-optimal climatic conditions during anthesis and grain ripening stage have been previously assessed, the role of photosynthesis efficiency and stomatal control on this resilience remains unexplored. This study aims to evaluate the relationship between grain yield and the post-anthesis flag leaf gas exchanges of Sicilian wheat landraces under irrigated and rainfed conditions and to compare these traits to modern durum (Triticum turgidum subsp. durum) and bread wheat (T. aestivum) varieties. Results indicate that wheat landraces respond to water availability similarly to modern varieties, reducing stomatal conductance by 26.8% and net photosynthesis by 18.1% under rainfed conditions, resulting in 10.6% lower grain yield compared to irrigated conditions. However, some landraces demonstrate comparable or even higher flag leaf net photosynthesis rates and lower transpiration levels, leading to higher yields in both rainfed and irrigated conditions, confirming their value as a source of gene pool for wheat breeding programs in drought-prone Mediterranean regions. [ABSTRACT FROM AUTHOR]

In this study, the effects of repeated cycles of drying and rehydration on some physiological traits were assessed in long shelf-life tomatoes cultivated in a typical semi-arid area of Southern Italy. Three Sicilian landraces (‘Custonaci’, ‘Salina’, and ‘Vulcano’) from the germplasm collection at CNR-IBE (Catania, Italy) and a commercial tomato mini-plum (‘Faino Hy., control) were investigated under three water regimes: DRY (no irrigation), IRR (long-season full irrigation) and REW (post-drought rewaterings). Net photosynthetic assimilation rate (Pn), leaf transpiration (E), stomatal conductance (gs), instantaneous water use efficiency (WUEi), leaf intercellular CO2 (Ci, ppm), and leaf temperature (°C), were measured during the growing season. At harvest (late July), fruit production per plant was measured and ripened fruits were analysed for total solids (TS), soluble solids (SS), reducing sugars (RS), vitamin C (AscA), and total phenols (TP). Pn promptly responded to rewatering (REW), quickly increasing immediately after irrigation, and declined with soil drying up. All genotypes had similar physiological pathways in DRY, but in IRR, ‘Faino’ had higher Pn (up to 31 μmol CO2 m−2s−1) and E (up to 18 mmol H2O m−2s−1). Stomatal conductance (gs) after rewatering steeply increased and quickly declined after that. All local landraces had the same gs in IRR and REW. Variations in RWC were less pronounced than those in other physiological parameters. WUEi in REW and DRY proceeded similarly (up to 3 μmol CO2 mmol H2O). Irrigation in REW significantly promoted plant productivity over the DRY control (up to +150% in ‘Vulcano’). TS and SS in REW were lower than those in DRY, but higher (+19 and +7%, respectively) than in IRR. Vitamin C was greater in DRY and REW (26 and 18% higher than in IRR, respectively). TP in all local tomatoes were significantly higher (up to +29% in ‘Vulcano’) than those in the commercial control. Water regime had a minor effect on TP in ‘Custonaci’ and ‘Salina’. Principal Component Analysis (PCA) provided information on the changes in physiological and fruit quality traits in tomatoes in relation to cultivars and water regimes. The results of this study also revealed that a water-saving irrigation strategy where few irrigations are applied after prolonged periods of drought might be profitable in terms of fruit production enhancement in long shelf-life tomatoes and that limited rewaterings in most cases, help retaining high levels of fruit quality traits.

Wheat landraces are traditional varieties that have evolved over generations in response to local environments and farming practices and therefore exhibit remarkable adaptability to challenging climatic conditions and low-input farming systems. While the suitability of Mediterranean landraces to non-optimal climatic conditions during anthesis and grain ripening stage have been previously assessed, the role of photosynthesis efficiency and stomatal control on this resilience remains unexplored. This study aims to evaluate the relationship between grain yield and the post-anthesis flag leaf gas exchanges of Sicilian wheat landraces under irrigated and rainfed conditions and to compare these traits to modern durum (Triticum turgidum subsp. durum) and bread wheat (T. aestivum) varieties. Results indicate that wheat landraces respond to water availability similarly to modern varieties, reducing stomatal conductance by 26.8% and net photosynthesis by 18.1% under rainfed conditions, resulting in 10.6% lower grain yield compared to irrigated conditions. However, some landraces demonstrate comparable or even higher flag leaf net photosynthesis rates and lower transpiration levels, leading to higher yields in both rainfed and irrigated conditions, confirming their value as a source of gene pool for wheat breeding programs in drought-prone Mediterranean regions.

Measuring ecophysiological responses of Eucalyptus clones grown under reduced water availability could assist in clonal selection for climate resilience. We hypothesized that clonal variation in chlorophyll a fluorescence was more readily detected than variations in leaf-level gas-exchanges when two-year-old E. grandis x E. urophylla hybrid clones (C1, C2, C3, and C4) were grown under rainfed (RF) and water-restricted (WR) conditions were evaluated during dry and rainy seasons, in the morning and midday diurnal periods. The C2 clone was the most drought tolerant as it had a similar net CO2 assimilation rate (A) considering the RF and WR conditions at midday during the dry season, while C1, C3, and C4 CO2 assimilation rates (A) decreased by 29.1 %, 28.3%, and 13%, respectively. This response was associated with a reduction to a lesser extent in leaf water potential, stomatal conductance (gs) and transpiration rates (E) (ca. 10%, 30% and 13% under WR, respectively), when compared to the other clones during the dry season at midday. The lower leaf to air vapor pressure deficit of C2 contributed to its greater water use efficiency (WUE), resulting in greater total dry mass gain. C1, C3 and C4 were less drought tolerant, decreasing gs, E and especially A under WR, resulting in lower WUE and total dry mass gain. Chlorophyll a fluorescence indexes were better indicators of drought tolerance compared to gas-exchange parameters in definition of drought tolerance of clonal Eucalyptus. Three drought sensitive clones showed low photochemical efficiency under WR, with the electron transport rate being impaired between photosystems II and I, indicated by the greater changes in photosynthetic performance index (PIabs). Under WR conditions, Fv/Fm, Ψ0, ΦE0, and PIabs decreased in all clones while ΦD0 and DI0/CS0 increased, with C2 showing the most stable responses suggesting that the photochemical apparatus was the less damaged by drought. Thus, C2 was the best clone for regions with water scarcity., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

Verticillium wilt of olive (VWO), caused by the soil borne fungus Verticillium dahliae, is one of the most relevant diseases affecting this crop worldwide. One of the best VWO management strategies is the use of tolerant cultivars. Scarce information is available about physiological and structural responses in the leaves of olive cultivars displaying different levels of tolerance to VWO. To identify links between this phenotype and variations in functional characteristics of the leaves, this study examined the structural and physiological traits and the correlations among them in different olive varieties. This evaluation was conducted in the presence/absence of V. dahliae. On the one hand, no leaf trait but the area was related to VWO tolerance in the absence of the pathogen. On the other hand, after inoculation, susceptible cultivars showed lower leaf area and higher leaf mass per area and dry matter content. Furthermore, at the physiological level, these plants showed severe symptoms resembling water stress. Analyzing the relationships among physiological and structural traits revealed differences between tolerant and susceptible cultivars both in the absence and in the presence of V. dahliae. These results showed that olive leaves of VWO-tolerant and VWO-susceptible cultivars adopt different strategies to cope with the pathogen. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a highly toxic heavy metal. Abscisic acid (ABA) is a regulator that has various functions in plants. To further explore the mechanism by which ABA alleviates Cd damage in plants, ABA and fluridone, which inhibits ABA biosynthesis, were separately sprayed on the leaves of Malus hupehensis Rehd. (M. hupehensis) seedlings treated with Cd. The root Cd2+ flux in vivo, the accumulation and transport of Cd2+ in roots, the cell death in roots and the transpiration rate in leaves were then analyzed. The results showed that the amount of cell death in roots gradually increased from 6 to 72 h in the Cd treatment. After spraying ABA on M. hupehensis leaves in the Cd treatment, the number of root cell deaths, the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in roots and the transpiration rate in leaves decreased significantly compared with those in the samples in the Cd-only treatment. In addition, the influx rate of Cd2+ in roots, the content of Cd in plants and the migration rate of Cd from the roots to the aerial parts were also significantly reduced. In contrast, all of these parameters increased significantly in M. hupehensis sprayed with fluridone under the Cd treatment. These results indicate that spraying ABA on leaves alleviates Cd damage in M. hupehensis roots by decreasing cell death as well as the contents of H2O2 and MDA in roots. Given that transpiration is the main driving force for the absorption and transport of inorganic salts in plants, our results showed that the alleviation of Cd damage in roots resulted from the reduced leaf transpiration rate, which decreased the influx and accumulation of Cd2+ in roots. [ABSTRACT FROM AUTHOR]

Increases in water use efficiency (WUE) and the reduction of negative impacts of high temperatures associated with high solar radiation are being achieved with the application of fine particle film of calcined and purified kaolin (KF) on the leaves and fruits of various plant species. KF was applied on young Coffea arabica and Coffea canephora plants before their transition from nursery to full sunlight during autumn and summer. The effects of KF were evaluated through the responses of leaf temperature (Tleaf), net CO2 assimilation rate (A), stomatal conductance (g s), transpiration (E), WUE, crop water stress index (CWSI), index of relative stomatal conductance (Ig), initial fluorescence (F0), and photosynthetic index (PI) in the first 2–3 weeks after the plant transitions to the full sun. All measurements were performed at midday. In Coffea plants, KF decreased the Tleaf up to 6.7°C/5.6°C and reduced the CWSI. The plants that were not protected with KF showed lower A , g s, E , and Ig than those protected with KF. C. canephora plants protected with KF achieved higher WUE compared with those not protected by 11.23% in autumn and 95.58% in summer. In both Coffea sp., KF application reduced F0, indicating reduced physical dissociation of the PSII reaction centers from the light-harvesting system, which was supported with increased PI. The use of KF can be recommended as a management strategy in the transition of Coffea seedlings from the nursery shade to the full sunlight, to protect leaves against the excessive solar radiation and high temperatures, especially in C. canephora during the summer. [ABSTRACT FROM AUTHOR]

Increases in water use efficiency (WUE) and the reduction of negative impacts of high temperatures associated with high solar radiation are being achieved with the application of fine particle film of calcined and purified kaolin (KF) on the leaves and fruits of various plant species. KF was applied on young Coffea arabica and Coffea canephora plants before their transition from nursery to full sunlight during autumn and summer. The effects of KF were evaluated through the responses of leaf temperature (Tleaf), net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E), WUE, crop water stress index (CWSI), index of relative stomatal conductance (Ig), initial fluorescence (F0), and photosynthetic index (PI) in the first 2–3 weeks after the plant transitions to the full sun. All measurements were performed at midday. In Coffea plants, KF decreased the Tleaf up to 6.7°C/5.6°C and reduced the CWSI. The plants that were not protected with KF showed lower A, gs, E, and Ig than those protected with KF. C. canephora plants protected with KF achieved higher WUE compared with those not protected by 11.23% in autumn and 95.58% in summer. In both Coffea sp., KF application reduced F0, indicating reduced physical dissociation of the PSII reaction centers from the light-harvesting system, which was supported with increased PI. The use of KF can be recommended as a management strategy in the transition of Coffea seedlings from the nursery shade to the full sunlight, to protect leaves against the excessive solar radiation and high temperatures, especially in C. canephora during the summer.

Verticillium wilt of olive (VWO), caused by the soil borne fungus Verticillium dahliae, is one of the most relevant diseases affecting this crop worldwide. One of the best VWO management strategies is the use of tolerant cultivars. Scarce information is available about physiological and structural responses in the leaves of olive cultivars displaying different levels of tolerance to VWO. To identify links between this phenotype and variations in functional characteristics of the leaves, this study examined the structural and physiological traits and the correlations among them in different olive varieties. This evaluation was conducted in the presence/absence of V. dahliae. On the one hand, no leaf trait but the area was related to VWO tolerance in the absence of the pathogen. On the other hand, after inoculation, susceptible cultivars showed lower leaf area and higher leaf mass per area and dry matter content. Furthermore, at the physiological level, these plants showed severe symptoms resembling water stress. Analyzing the relationships among physiological and structural traits revealed differences between tolerant and susceptible cultivars both in the absence and in the presence of V. dahliae. These results showed that olive leaves of VWO-tolerant and VWO-susceptible cultivars adopt different strategies to cope with the pathogen.

Wood ash as a soil amendment has gained wide spread acceptance in the recent years as a sustainable alternative to chemical fertilizers, although information regarding the effects of its application on maize growth and yield in the context of climate change and increasing drought severity is lacking till date. In the present study, field and pot trials were carried out at the experimental farm of the University of Padova at Legnaro (NE Italy) in a silty-loam soil in order to investigate the effects of soil amendment with wood ash (0.1% w/w, incorporated into the 0.2-m top soil) on the bioavailability of mineral elements and their uptake by maize. Characteristics analyzed included plant growth, leaf transpiration dynamics, and productivity in two contrasting hybrids, P1921 (drought sensitive) and D24 (drought tolerant). Wood ash contained relevant amounts of Ca, K, Mg, P, and S, and hazardous levels of Zn (732 mg kg−1), Pb (527 mg kg−1), and Cu (129 mg kg−1), although no significant changes in total soil element concentration, pH, and electrical conductivity were detected in open field. Ash application led to a general increasing trend of diethylene triamine penta-acetic acid (DTPA)-extractable of various elements, bringing to higher grain P in D24 hybrid, and Zn and Ni reductions in P1921 hybrid. Here, the results demonstrated that ash amendment enhanced shoot growth and the number of leaves, causing a reduction of harvest index, without affecting grain yield in both hybrids. The most relevant result was a retarded inhibition of leaf transpiration under artificial progressive water stress, particularly in the drought-tolerant D24 hybrid that could be sustained by root growth improvements in the field across the whole 0–1.5 m soil profile in D24, and in the amended top soil in P1921. It is concluded that woody ash can be profitably exploited in maize fertilization for enhancing shoot and root growth and drought tolerance, thanks to morphological and physiological improvements, although major benefits are expected to be achieved in drought tolerant hybrids. Attention should be payed when using ash derived by metal contaminated wood stocks to avoid any health risk in food uses.

Wood ash as a soil amendment has gained wide spread acceptance in the recent years as a sustainable alternative to chemical fertilizers, although information regarding the effects of its application on maize growth and yield in the context of climate change and increasing drought severity is lacking till date. In the present study, field and pot trials were carried out at the experimental farm of the University of Padova at Legnaro (NE Italy) in a silty-loam soil in order to investigate the effects of soil amendment with wood ash (0.1% w/w, incorporated into the 0.2-m top soil) on the bioavailability of mineral elements and their uptake by maize. Characteristics analyzed included plant growth, leaf transpiration dynamics, and productivity in two contrasting hybrids, P1921 (drought sensitive) and D24 (drought tolerant). Wood ash contained relevant amounts of Ca, K, Mg, P, and S, and hazardous levels of Zn (732 mg kg−1), Pb (527 mg kg−1), and Cu (129 mg kg−1), although no significant changes in total soil element concentration, pH, and electrical conductivity were detected in open field. Ash application led to a general increasing trend of diethylene triamine penta-acetic acid (DTPA)-extractable of various elements, bringing to higher grain P in D24 hybrid, and Zn and Ni reductions in P1921 hybrid. Here, the results demonstrated that ash amendment enhanced shoot growth and the number of leaves, causing a reduction of harvest index, without affecting grain yield in both hybrids. The most relevant result was a retarded inhibition of leaf transpiration under artificial progressive water stress, particularly in the drought-tolerant D24 hybrid that could be sustained by root growth improvements in the field across the whole 0–1.5 m soil profile in D24, and in the amended top soil in P1921. It is concluded that woody ash can be profitably exploited in maize fertilization for enhancing shoot and root growth and drought tolerance, thanks to morphological and physiological improvements, although major benefits are expected to be achieved in drought tolerant hybrids. Attention should be payed when using ash derived by metal contaminated wood stocks to avoid any health risk in food uses. [ABSTRACT FROM AUTHOR]

Anthropogenic aerosols could alter multiple meteorological processes such as radiation regime and air temperature, thereby modifying plant transpiration. However, the lack of field observations at leaf and plant level hinders our ability to understand how aerosols could affect plant water use.Aerosol concentrations in northern China fluctuate periodically over a wide range. Taking advantage of this unique natural experiment opportunity, we conducted a series of physiological and environmental measurements at different times of the day to explore diurnal aerosols' effect on leaf transpiration and sap flow of planted poplar saplings (Populus × canadensis Moench).We found that high aerosol concentrations suppressed sun leaf transpiration by reducing leaf‐to‐air vapour pressure deficit (VPDleaf), while had no effect on shade leaf transpiration mainly because the negative effect of reduced VPDleaf on transpiration offset the positive effects of the increased stomatal conductance (gs). As aerosol concentration increased, the gs of both sun and shade leaves decreased more rapidly with an increase in VPDleaf, which caused their transpiration rates to become less sensitive to VPDleaf. Similarly, aerosols reduced sap flow density and its sensitivity to VPD.Synthesis. Our study provided observational evidence on aerosols' effects on plant transpiration at the leaf and canopy scales. The reduced transpiration and stronger stomatal control indicated that plant water use becomes more conservative under elevated aerosol concentrations. [ABSTRACT FROM AUTHOR]

Quantifying heat and mass exchanges processes of plant leaves is crucial for detailed understanding of dynamic plant-environment interactions. The two main components of these processes, convective heat transfer, and transpiration, are inevitably coupled as both processes are restricted by the leaf boundary layer. To measure leaf heat capacity and leaf heat transfer coefficient, we thoroughly tested and applied an active thermography method that uses a transient heat pulse to compute τ, the time constant of leaf cooling after release of the pulse. We validated our approach in the laboratory on intact leaves of spring barley (Hordeum vulgare) and common bean (Phaseolus vulgaris), and measured τ-changes at different boundary layer conditions.By modeling the leaf heat transfer coefficient with dimensionless numbers, we could demonstrate that τ improves our ability to close the energy budget of plant leaves and that modeling of transpiration requires considerations of convection. Applying our approach to thermal images we obtained spatio-temporal maps of τ, providing observations of local differences in thermal responsiveness of leaf surfaces. We propose that active thermography is an informative methodology to measure leaf heat transfer and derive spatial maps of thermal responsiveness of leaves contributing to improve models of leaf heat transfer processes.

Quantifying heat and mass exchanges processes of plant leaves is crucial for detailed understanding of dynamic plant-environment interactions. The two main components of these processes, convective heat transfer, and transpiration, are inevitably coupled as both processes are restricted by the leaf boundary layer. To measure leaf heat capacity and leaf heat transfer coefficient, we thoroughly tested and applied an active thermography method that uses a transient heat pulse to compute τ, the time constant of leaf cooling after release of the pulse. We validated our approach in the laboratory on intact leaves of spring barley (Hordeum vulgare) and common bean (Phaseolus vulgaris), and measured τ-changes at different boundary layer conditions.By modeling the leaf heat transfer coefficient with dimensionless numbers, we could demonstrate that τ improves our ability to close the energy budget of plant leaves and that modeling of transpiration requires considerations of convection. Applying our approach to thermal images we obtained spatio-temporal maps of τ, providing observations of local differences in thermal responsiveness of leaf surfaces. We propose that active thermography is an informative methodology to measure leaf heat transfer and derive spatial maps of thermal responsiveness of leaves contributing to improve models of leaf heat transfer processes. [ABSTRACT FROM AUTHOR]

An experimental vegetative climatic unit (VCU) consisting of two identical climatic chambers—experimental (CC-1) and control (CC-2)—was developed. The VCU allows long-term cultivation of higher plants under various constant microclimate conditions, moisture supply, and CO2 concentration. The basic scheme of the VCU and its parameters and operation are considered. As a result of a long (50 days) vegetation experiment in the VCU, we evaluated the effect of a double atmospheric CO2 concentration on СО2/Н2О gas exchange, the water status of leaves, and the biological productivity of pea (Pisum sativum L.) plants. The water status of the plant leaves of the experimental and control variants was evaluated based on the water potential value on the surface of the apoplast of the substomatal cavity. Compared to control plants under conditions of double CO2 concentration, a 1.5-fold increase in leaf, stem, and root weight was noted. The preservation of proportional organ growth under growing conditions at a double concentration of atmospheric CO2 in pea varieties with contrasting biological productivity—the highly productive Alpha variety and the unproductive Medovik variety—indicated the absence of varietal specificity of the pea growth reaction to increased CO2. The maximum yield of chlorophyll FSII fluorescence, photosynthetic CO2/H2O-gas exchange of intact leaves, measured at normal CO2 concentration, as well as the water status of the leaves, were the same in the plants of the experimental and control variants of the Medovik variety. With other conditions being equal, a double CO2 concentration of under nonlimiting by the water regime and mineral nutrition conditions of pea plant growing formed a leaf that does not differ from the leaf formed under a normal CO2 concentration. An increase in the biological productivity of peas under these conditions was provided by an increased photosynthetic carboxylation activity under increased atmospheric CO2 concentration and the formation of higher stem and leaf phytomass. As a result, it was concluded that the reaction of the photosynthetic and growth functions of pea plants to long-term cultivation under conditions of a double atmospheric CO2 concentration at nonlimiting by mineral nutrition and water supply conditions did not cause imbalances in growth and development. The reaction of the photosynthetic and growth functions of pea plants was within the physiological norm of the reaction of a pea plant to stress. [ABSTRACT FROM AUTHOR]

Among the pragmatic approaches to addressing the issue of climate change is reduction of its anthropogenic causes (such as emissions from burning of fossil fuels and indiscriminate removal of vegetation cover) and making of conscious efforts toward increasing global vegetation cover. Based on the desirable qualities of afforestation species, this study aimed to quantify the rate of leaf transpiration in seven selected tree species in Ogbomoso Nigeria, with a view to ascertaining their suitability for afforestation of water stress habitats. The mean quantity of water transpired per cm² area of ten randomly selected mature leaves of seven tree species from the study location (80 10' 12.217''N, 40 15'12.607''E - 80 9' 45.834''N, 40 16' 6.209''E) was determined as a difference in the weight of a 4cm² dry cobalt chloride paper (DCCP) and wet cobalt chloride paper stuck to adaxial/upper and abaxial/lower leaf surfaces until the blue DCCP completely turned to pink, and the time taken for this to happen was recorded. The rate of transpiration was also calculated in mg/cm²/min of each leaf surface by dividing the amount of water transpired/cm² area by the respective time taken, and the means for the seven tree species were obtained. Higher mean rates of water transpiration in mg/cm²/min were recorded on the abaxial (18.6±2.4 - 30.6±1.8 in Psidium guajava and Ficus exasperata respectively) than the adaxial (14.4±1.8 - 25.2±6.0, also in P. guajava and F. exasperata) leaf surfaces. Evidence from the statistical analysis led to the conclusion that F. umbellata and F. exasperata are better atmospheric humidifiers than the other five tree species studied which instead, are better water conservers. The rate of leaf transpiration in four of the latter namely; Anacardium occidentale, F. benjamina, Mangifera indica and P. guajava are on a par with the fifth i.e. Azadirachta indica, the widely acclaimed afforestation species of dry lands. Therefore, the seven tree species studied are suitable candidates for afforestation of dry areas, the two humidifiers where increased atmospheric water vapour is desired, and the water conservers for water-stress environments. [ABSTRACT FROM AUTHOR]

• The three-dimensional spatial structure of summer maize was clarified. • The photosynthetically active radiation of each leaf unit was obtained. • Considering spatial heterogeneity, the leaf transpiration model has been upgraded to individual plant. Plant transpiration research is the foundation for improving the efficiency of agricultural water resource utilization and ensuring food production safety. It is an important content of agricultural production and water resource utilization research. However, spatial heterogeneities of leaf size and positions affect the estimation of transpiration. In this study, summer maize on the North China Plain was taken as the research object. Based on the measured data of the photosynthetic apparatus, morphogenesis and stem flow meter, the transpiration variation rule of summer maize leaves was analyzed, and the spatial distribution model of photosynthetically active radiation based on plant morphogenesis was constructed. Considering the spatial heterogeneities of leaf size and positions, the individual-plant scale transpiration model was upgraded. The reliability of transpiration model at individual plant scale was verified. The results showed that: i) the transpiration rate of leaves with different leaf positions, positive and negative leaves at the same leaf position and different parts of the same leaf were significantly different. ii) Based on the measured data, the structure of summer maize with spatial coordinates was obtained, and a calculation model for solar radiation reaching the top of the plants and a calculation model for photosynthetically active radiation reaching the surface of the leaves were constructed. Based on the different absorption, reflection, and transmission of radiation by summer maize leaves, the photosynthetically active radiation of each part of the leaves was characterized. iii) A plant transpiration model was constructed by combining the leaf panel transpiration model with the spatial distribution model of photosynthetically active radiation in summer maize plants, and, the determination coefficients between the simulated and the measured values of the individual plant scale transpiration rate were all above 0.95, the consistency index was close to 1.0, and the RMSE was in range of 12.41–16.64 g h−1. The individual plant transpiration obtained after simulated accumulation could meet the simulation accuracy. The results achieved the scale improvement of the leaf transpiration to individual plant transpiration. [ABSTRACT FROM AUTHOR]

A clear understanding of plant transpiration is a crucial step for water cycle and climate modeling, especially for arid ecosystems in which water is one of the major constraints. Traditional field measurements of leaf scale transpiration are always time-consuming and often unfeasible in the context of large spatial and temporal scales. This study focused on a dominant native plant in the arid land of central Asia, Haloxylon ammondendron, with the aim of deriving the leaf-scale transpiration through hyperspectral reflectance using Partial Least Squares Regression (PLSR) analysis. The results revealed that the PLSR model based on the first-order derivative spectra at wavelengths selected through stepwise regression analysis can closely trace leaf transpiration with a high accuracy (R2 = 0.78, RMSE = 1.62 µmol g-1 s-1). The accuracy is also relatively stable even at a spectral resolution of 10 nm, which is very close to the bandwidths of several running satellite-borne hyperspectral sensors such as Hyperion. The results also proved that the first-order derivative spectra within the shortwave infrared (SWIR) domain, especially at 2435, 2440, 2445, and 2470 nm, were critical for PLSR models to predict leaf transpiration. These findings highlight a promising strategy for developing remote sensing methods to potentially characterize transpiration at broad scales.

Deficit irrigation is a valid alternative to conventional irrigation to save water while maintaining high productivity in tomatoes. However, crop sensitivity to water stress due to deficit irrigation may change with the growth stage. To assess the physiological and agronomic responses of processing tomatoes to deficit irrigation applied at critical stages, a field experiment was conducted in a coastal site of Southern Italy, where seven irrigation treatments differing for daily evapotranspiration (ETc) restored (100%—full or 50%—deficit) and the time of watering (long-season or limited to the vegetative period or to flowering) were applied to processing tomatoes cv. Hypeel F1. Plants continuously irrigated and those irrigated only at flowering maintained higher rates of leaf transpiration (E) and stomatal conductance (gs) over those irrigated only during the vegetative period. Fruit yield was the greatest under long-season full irrigation (51 t ha−1). Severe soil water deficit during flowering, more than during the vegetative period, adversely affected crop productivity. Irrigation water use efficiency (IWUE) was maximized under long-season deficit irrigation (>19 kg m−3) or deficit irrigation during flowering (>16 kg m−3). E and gs measured at early or mid-flowering may be adopted as valuable indicators to predict crop productivity; however, they may be altered under high vapor pressure deficit (VPD). Predawn water potential, being little affected by VPD, is a more reliable parameter than leaf transpiration and stomatal conductance under these climatic conditions.

Abstract: Low availability of inorganic phosphorus (P) is considered a major constraint for crop productivity worldwide. A unique set of 266 chickpea (Cicer arietinum L.) genotypes, originating from 29 countries and with diverse genetic background, were used to study P‐use efficiency. Plants were grown in pots containing sterilized river sand supplied with P at a rate of 10 μg P g−1 soil as FePO4, a poorly soluble form of P. The results showed large genotypic variation in plant growth, shoot P content, physiological P‐use efficiency, and P‐utilization efficiency in response to low P supply. Further investigation of a subset of 100 chickpea genotypes with contrasting growth performance showed significant differences in photosynthetic rate and photosynthetic P‐use efficiency. A positive correlation was found between leaf P concentration and transpiration rate of the young fully expanded leaves. For the first time, our study has suggested a role of leaf transpiration in P acquisition, consistent with transpiration‐driven mass flow in chickpea grown in low‐P sandy soils. The identification of 6 genotypes with high plant growth, P‐acquisition, and P‐utilization efficiency suggests that the chickpea reference set can be used in breeding programmes to improve both P‐acquisition and P‐utilization efficiency under low‐P conditions. [ABSTRACT FROM AUTHOR]

In this experiment, the responses of plant growth, gas exchange parameters, and ion concentration to different levels of irrigation water salinity (ECiw of 0.9, 1.6, 2.7, 4.7 and 7.0 dS·m-1) and leaching fractions (LFs of 0.17, 0.29) were investigated in hot pepper plants. The pot experiment was conducted using a completely randomized block design with four replications in a rain shelter. Results showed that the height of the hot pepper plants decreased as the ECiw was increased from 25 d after transplanting (DAT) and increased when the LF was increased from 55 DAT. Neither the ECiw nor the LF influenced the root length. An increase in the ECiw caused the suppression of the stem diameter (SD); leaf length; leaf area; leaf chlorophyll content (CCI); dry biomass of roots, stems, and leaves; net photosynthesis (Pn); stomatal conductance (gS); transpiration rate (Tr); and intercellular CO2 concentration (Ci). An increase in the LF caused the SD, leaf length, leaf area, and dry biomass of stems and leaves to increase. However, the dry biomass of roots and the Pn, gS, Tr, and Ci were not significantly affected by the LF, except for the Ci measured on 23 DAT and the Tr on 76 DAT. The Na+ concentrations in the roots and stems increased, whereas the K+/Na+ ratios decreased as the ECiw increased. An increase in the LF led to a decrease in the Na+ concentration of the roots and stems, whereas there was an increase in the K+ concentration in the stems and the K+/Na+ ratios in the roots and stems. Collectively, an increase in the ECiw had an adverse effect on plant growth and gas exchange and led to the accumulation of the Na+ concentration in the roots and stems, whereas an increase in the LF enhanced plant growth, leaf transpiration, and K+ concentration and reduced the accumulation of the Na+ concentration in the roots and stems. We suggest that higher quantity of water should be applied in higher saline irrigation for satisfactory performance for hot pepper growth. [ABSTRACT FROM AUTHOR]

• Reversibly fire-retardant thermal regulation material is prepared by mimicking leaves. • Composite has great fire resistance, temperature regulation and mechanical property. • Reversible fire resistance is achieved by water evaporation and phase-change behavior. The demand for advanced fire-retardant wearable materials has increased with a rise in fire disasters in modern society. However, traditional fabrics have some drawbacks including non-temperature regulation, non-recyclability and contaminated products. Here, inspired by leaf transpiration, we prepared a reversibly flame-retardant thermal regulation material (LPWH). Wood cellulose skeleton is expected to be a reinforced mechanical scaffold by imitating the role of leaf vein for water collection and transportation. In parallel, to mimic the mesophyll cells around leaf vein, a hydrophilic and porous phase-change hydrogel aggregation is prepared by anchoring polyethyleneglycoldiacrylate-co-sodium vinylsulfonate copolymer on cellulose fibers and subsequent in-situ assembly of sodium alginate. This precise combination creates an artificial transpiration tissue, achieving effective heat dissipation and temperature regulation via water transpiration and phase-change behavior of hydrogel aggregation. LPWH shows a longer ignited time of 150 s (71% extension), a lower total smoke release of 22.3 m2/m2 (76% reduction), together with an ultralow fire growth index of 2.4 compared to commercial fire-retardant cotton fabric. Moreover, reversible fire retardancy (30 cycles) and great mechanical property (351 times higher than pure phase-change hydrogel) are demonstrated, suggesting LPWH can be the next generation of the pollution-free, recyclable temperature-regulated fireproof suit. [ABSTRACT FROM AUTHOR]

Harvestmen ( Arachnida, Opiliones) are arachnids that rely on chemicals for communication and are particularly dependent on high humidity. The harvestman Jussara spec. ( Sclerosomatidae) clearly prefers to rest on the stem and leaves of Psychotria suterella Muell. Arg. ( Rubiaceae), a plant having a complex architecture of overlapping branches. So far, few studies have focused on understanding how harvestmen find their host plant and the benefits associated with the selected plant. Here, we investigated cues harvestmen may exploit to find P. suterella and the potential benefits for harvestmen of this interaction. To address how harvestmen find the plant, we tested two non-exclusive hypotheses: harvestmen use chemicals from conspecifics, and/or harvestmen use chemicals from plants. For the first hypothesis, we assessed the number of harvestmen choosing P. suterella with or without chemicals of Jussara spec. on the main stem. We did not find evidence that Jussara spec. uses chemicals from conspecifics to select P. suterella, at least in isolation, without any mechanical stimuli such as stem texture or size. For the second hypothesis, we tested harvestman behavior exposed to volatiles from P. suterella, a non-preferred host plant - Impatiens walleriana Hook.f. ( Balsaminaceae) - and a blank treatment, both in a triangular arena and in a Y-tube olfactometer. We also found no evidence that the harvestmen use plant volatiles to find it. We also tested two non-exclusive hypotheses regarding the benefits of selecting P. suterella for harvestmen. The first hypothesis is that P. suterella offers a higher humidity than other plants in the micro-environment surrounding the leaves because of a high leaf transpiration rate. Harvestmen could benefit from this because they rest with the body in contact with the leaf or at less than 5 mm from it. We did not find evidence that leaf transpiration rate is important for Jussara spec., as P. suterella did not present high rates compared to other local species. The second hypothesis is that the leaves of P. suterella provide a better shadow than other plants, acting as a sun shade due to its complex architecture with overlapping leaves. We measured light passage through the leaves of P. suterella and three other local species and found that less light passes through the leaves of P. suterella, which therefore provides darker shadow. This potentially provides a favorable micro-climate for harvestmen, which might help to explain the micro-habitat preference of Jussara spec. [ABSTRACT FROM AUTHOR]

Euphorbia pulcherrima Wild.'Lilo' was grown in containers in 60% peat, 30% perlite and 10% clay (v/v) mixture, with different irrigation treatments based on soil water potential. Plants were watered at two levels of drought stress: -50kPa or wilting. The treatments were applied at different stages of plant development for a month or soil was brought to the moisture stress only twice. Additionally, some plants were watered at -50 kPa during the entire cultivation period while the control plants were watered at -5kPa. Plants were also kept at maximum possible moisture level (watering at -0,5kPa) or close to it (-1.OkPa) through the entire growing period. Soil water potential was measured with tensiometer. Drought stress applied during entire cultivation period or during the flushing stage caused significant reduction in transpiration and conductance of leaves. Stress applied during bract coloration stage had not as great effect on the stomatal conductance and transpiration of leaves as the similar stress applied during the flushing stage. High soil moisture increased stomatal conductance and transpiration rate, respectively by 130% and 52% (flushing stage), and 72% and 150% (bract coloration stage) at maximum, compared to the control.

This research aimed to evaluate the gas exchange and growth index of Brachiaria decumbens under five water supply (3.84, 4.39, 6.19, 8.62 and 10.46 mm day-1). A completely randomized with split-plot design with five irrigation depth being the parcels and ages (10, 17, 24 and 31 days), the subparcels, with four replicates. It was observed interaction between irrigation depth and ages for leaf transpiration, leaf temperature, rate of photosynthesis and leaf weight ratio. Quadratic responses with minimum values were observed to the internal CO2 concentration and specific leaf area (0.0055 m² leaf g-1 leaf) with advance in ages. The internal concentration of CO2 revealed values of 220.09 and 176.20 ppm to 10 and 31 days, respectively, withminimum (173.68 ppm) to 27 days. It was observed quadratic response with maximum value (25.04 g m-2 leaf day-1) to the net assimilation rate with increasing ages. Decreasing linear responses were observed to the relative growth rate and leaf area ratio with increasing ages. The relative growth rate presented values of 0.097 and 0.048 g g-1 day-1, with 10 and 31 days, respectively. The growth ages provided changes on gas exchange and growth index of Brachiaria grass, however, these characteristics are little influenced by irrigation depth under the conditions of this study.ResumoObjetivou-se com esse estudo avaliar trocas gasosas e índices de crescimento no capim-braquiária manejado sob cinco lâminas de irrigação (3,84; 4,39; 6,19; 8,62 e 10,46 mm dia-1) e quatro idades, num delineamento inteiramente casualizado em arranjo de parcelas subdivididas, sendo as lâminas de irrigação estudadas nas parcelas e as idades (10, 17, 24 e 31 dias) nas subparcelas, com quatro repetições. Constatou-se interação entre lâminas de irrigação e idades nas variáveis: transpiração foliar, temperatura da folha, taxa de fotossíntese e razão de peso foliar. Verificou-se resposta quadrática com ponto de mínimo para a concentração interna de CO2 e área foliar específica (0,0055 m² de folha g-1 de folha) em função do avanço nas idades. A concentração interna de CO2 apresentou valores estimados em 220,09 e 176,20 ppm aos 10 e 31 dias de crescimento, respectivamente, com valor mínimo (173,68 ppm) aos 27 dias. Verificou-se resposta quadrática com ponto de máximo (25,04 g m-2 de folha dia-1) para a taxa de assimilação líquida com o aumento nas idades. Observou-se resposta linear decrescente para taxa de crescimento relativo e razão de área foliar com aumento nas idades. A taxa de crescimento relativo revelou valores de 0,097 e 0,048 g g-1 dia-1, com 10 e 31 dias de crescimento, respectivamente. As idades de crescimento proporcionam mudanças nas trocas gasosas e nos índices de crescimento do capim-braquiária, porém, tais variáveis são pouco influenciadas pelaslâminas de irrigação nas condições do presente estudo.

Estudos sobre os fatores envolvidos na adaptação das plantas micropropagadas ao ambiente ex vitro são imprescindíveis para definir quais os procedimentos devem ser utilizados durante a fase de aclimatização. O objetivo deste trabalho foi avaliar a contribuição da densidade estomática e da presença de cera epicuticular no controle da perda de água, em folhas de bananeiras micropropagadas. Para tanto, brotações axilares oriundas da etapa de multiplicação in vitro foram enraizadas por 24 dias, em meio MS, contendo 1mg L-1 de ácido naftalenoacético (ANA) e 6g L-1 de ágar e, posteriormente, foram aclimatizadas por 120 dias. Os tratamentos consistiram de folhas formadas in vitro e em diferentes estádios de aclimatização, tais como: T1 - folhas de plantas ao final da fase de enraizamento in vitro; T2 - folhas persistentes de plantas aos 30 dias de aclimatização; T3 - novas folhas de plantas aos 30 dias de aclimatização (folhas de transição); T4 - folhas de transição de plantas aclimatizadas por 60 dias; T5 e T6 - novas folhas de plantas aclimatizadas por 60 dias e 120 dias, respectivamente. Foram avaliados os seguintes parâmetros: a densidade estomática, o conteúdo relativo de água e a presença de cera epicuticular. Foi verificado que folhas de plantas provenientes da fase de enraizamento in vitro, em ambiente mixotrófico, apresentam reduzido controle sobre a perda de água e alta densidade estomática. A reduzida transpiração das folhas formadas na fase de aclimatização pode ser atribuída ao menor número de estômatos por unidade de área foliar, à maior capacidade destes em restringir a perda de água e à presença de cera epicuticular.Studies concerning factors involved in the adaptation of micropropagated plants to ex vitro conditions are indispensable to define which procedures should be used during the acclimatization phase. The objective of this research was to evaluate the presence of stomata and epicuticular wax on water loss control in micropropagated banana plants. For 24 days axillary buds were rooted in MS medium supplemented with NAA (1mg L-1) and agar (6g L-1), and afterwards the plantlets were acclimatized for 120 days. The treatments consisted of the evaluation of in vitro leaves and at different acclimatization stages, as follows: T1 - leaves of plants at the end of the in vitro rooting phase T2 - persistent leaves of plants after 30 days of acclimatization; T3 - new leaves from plants after 30 days of acclimatization (transition leaves); T4 - transition leaves from plants after 60 days of acclimatization; T5 and T6 - new leaves from plants after 60 and 120 days of acclimatization, respectively. Data regarding stomatal density, relative water content and presence of epicuticular wax were also evaluated. It was verified that new leaves from plants rooted in vitro under mixotrophic condition presented hight stomatal density and hence a reduced control of water loss. The reduced transpiration of leaves formed during the acclimatization phase can be attributed to the small number of stomata per unit of leaf area associated to the largest capacity of these in restricting water loss, and the presence of epicuticular wax.

Long-storage tomato is a drought-tolerant plant traditionally cultivated under no water supply in semi-arid areas of Italy. In 2009, physiological traits of ten “long-storage” tomato lines cultivated under no irrigation were screened for low soil water tolerance. Leaf relative water content (RWC), proline content and leaf transpiration ( E ) were measured throughout the growing season. Instantaneous leaf water use efficiency was also calculated on a single date, as the ratio between net photosynthesis ( A ) and E . Close relationships were observed among the physiological parameters, positive for E vs . RWC and inverse for RWC and E vs . proline. Results indicate that the increase in proline concentration involves a water stress tolerance, and genotypes more sensitive to soil water deficit respond to drought stress through less proline in leaves. Close significant linear relationships (positive with RWC and E , negative with proline) were also found between fruit yield and all the physiological parameters examined. Among them, the most reliable indicator for yield prediction under water restriction was leaf transpiration rate as measured at the flowering stage. The study made it possible to understand the complex relationships between physiological processes, drought tolerance, and plant productivity in long-storage tomato, and to identify those traits that regulate plant physiology under low water availability. [ABSTRACT FROM AUTHOR]

A clear understanding of plant transpiration is a crucial step for water cycle and climate modeling, especially for arid ecosystems in which water is one of the major constraints. Traditional field measurements of leaf scale transpiration are always time-consuming and often unfeasible in the context of large spatial and temporal scales. This study focused on a dominant native plant in the arid land of central Asia, Haloxylon ammondendron, with the aim of deriving the leaf-scale transpiration through hyperspectral reflectance using Partial Least Squares Regression (PLSR) analysis. The results revealed that the PLSR model based on the first-order derivative spectra at wavelengths selected through stepwise regression analysis can closely trace leaf transpiration with a high accuracy (R² = 0.78, RMSE = 1.62 μmol g-1 s-1). The accuracy is also relatively stable even at a spectral resolution of 10 nm, which is very close to the bandwidths of several running satellite-borne hyperspectral sensors such as Hyperion. The results also proved that the first-order derivative spectra within the shortwave infrared (SWIR) domain, especially at 2435, 2440, 2445, and 2470 nm, were critical for PLSR models to predict leaf transpiration. These findings highlight a promising strategy for developing remote sensing methods to potentially characterize transpiration at broad scales. [ABSTRACT FROM AUTHOR]

The anatomical and epidermal characteristics, as well as the physiological response, of 'Colombia' ecotype cape gooseberry plants treated or untreated with foliar applications of kaolin at 2 irrigation levels (well-irrigated plants vs. water-stressed plants) were evaluated. Relative Water Content (RWC), stomatal density, and chlorophyll index were reduced under water stress. Water stress increased leaf temperature and trichome density. In water-stressed plants, the foliar application of kaolin decreased transpiration rates, leaf temperature, trichome density, and leaf thickness. Kaolin also improved the plant height, total plant dry mass, water-use efficiency, and increased stomatal density in water-stressed plants. The results suggest that kaolin may be a useful tool to mitigate the negative effects of water stress and may improve the efficient use of water in cape gooseberry plants with especial water conditions. [ABSTRACT FROM AUTHOR]

The bean crop is of great importance for human consumption as a source of protein. One of the most limiting insect pests of this crop in Colombia is the whitefly, Trialeurodes vaporariorum (Westwood). Currently, various nonchemical pest control alternatives for cleaner production are being sought. This study aimed to determine the influence of kaolin on the development of populations of whitefly in greenhouses, and its effect on the physiological characteristics of the bean crop [Phaseolus vulgaris (L.)]. This work was conducted in the greenhouses of the Universidad Nacional de Colombia, in Bogotá. Three experiments were carried out and four treatments were evaluated: 1) control (without any insecticide), 2) synthetic chemical insecticides, and foliar applications of kaolin at 3) 2.5%, and 4) 5% (W/V). Generally, the results showed a high percentage of efficacy (≈91%) on whitefly control in plants treated with 5% kaolin, compared with the plants not treated with insecticides in the three different experiments. In addition, foliar applications of kaolin decreased transpiration by 40% and enhanced by 43% the contents of leaf chlorophyll without affecting bean yield. In conclusion, the use of kaolin particle can be considered as an alternative tool in a program of agricultural management on the bean crop since it can control a high percentage of whitefly and it may help the plant physiology, especially under conditions of abiotic stress such as drought stress. [ABSTRACT FROM AUTHOR]

Mass transport in porous materials is widespread in nature, and its usefulness attracts large attention for engineering applications. Plant leaves have nano-/microporous structures to pull water from root to the tip of leaves, and they finally release water to the air. In this hydraulic phenomenon called transpiration, plant leaves provide the main driving force for water transport in plants without any mechanical pump system. The morphological structure of plant leaves has been optimized through a long history of evolution to adapt to the environmental changes. In this aspect, we focus on the morphological features of plant leaves, which probably enhance leaf transpiration. The tissue organization in the hydraulic pathways inside the leaves for transpiration was investigated in this study. Inspired by the morphological structure of mesophyll cells in a plant, two analogous models were fabricated using hydrogel to study the effect of pore size on water transport. One model had nanoporous unitary structure, and the other had nano-/microporous hierarchical structure. As a result, the hydrogel model with nano-/microporous hierarchical structure induced higher evaporation and greater swelling ratio, compared with the model with nanoporous unitary structure. X-ray images of the water transport in the hydrogel models show that the porous structures of mesophyll cells can generate the Laplace pressure at the water-air interface in the air spaces. [ABSTRACT FROM AUTHOR]

The effects of nutrient deficiency on shoot length and physiological behavior of lulo plants grown under greenhouse conditions were evaluated. Four-month-old lulo (Solanum quitoensevar.septentrionale) seedlings were transplanted into 2-L plastic pots containing peat as substrate. Treatments were established after the plants acclimatized for 14 days: (1) Control, without any type of fertilization, (2) fertilizer application to soil (with macro- and micronutrients), and (3) fertilizer application to soil plus foliar sprays containing nitrogen at a concentration of 125, 250, and 500 ppm N from urea. Lulo plants grown without any fertilizer were shorter and had lower plant height, dry mass, leaf chlorophyll content (SPAD readings), and Fv/Fm ratio than plants grown with fertilizer. Also, our results revealed that the lack of nutrients caused a greater amount of biomass in roots. Foliar sprays of urea did not have any positive effect on the evaluated variables. These results indicate that a poor nutritional status can be limiting the foliar uptake, causing a lack of response of lulo plants to foliar applications of N as a tool under nutritional stress conditions. [ABSTRACT FROM AUTHOR]

Plant cultivars with high biomass production may have a high potential for being used in integrated water treatment and plant production system. The highly productive hybrid Napier grass cultivar, Pennisetum purpureum × Pennisetum americanum cv. Pakchong1, may be a candidate species for being used in such systems. We studied the effects of inorganic nitrogen form (NH 4 + , NH 4 NO 3 or NO 3 − ) on growth, morphology, N uptake, water content and mineral allocation in this species under hydroponic conditions at equimolar concentrations (500 μmol N L −1 ). Generally, the N-form significantly affected growth, biomass allocation and tissue nutrient and mineral composition of the plants. The hybrid Napier grass grew better on NH 4 + compared to NO 3 − , and the plants supplied with NH 4 + contained three times more chlorophylls than plants supplied with NO 3 − alone or NO 3 − combined with NH 4 + . The morphology of the plants was, however, not affected by N source, except for the shoot to root ratio, which was lower in NH 4 + -fed plants. The relative water content of the leaves was lowest in the NH 4 + -fed plants, but the transpiration rate was not affected, indicating that NH 4 + nutrition and the associated low tissue concentration of K had negative effects on the water use efficiency of the plants. The study suggests that this hybrid Napier grass cultivar may be a new candidate species for use in integrated water treatment and plant production systems. [ABSTRACT FROM AUTHOR]

ABSTRACT Mangroves are expanding into warm temperate-zone salt marsh communities in several locations globally. Although scientists have discovered that expansion might have modest effects on ecosystem functioning, water use characteristics have not been assessed relative to this transition. We measured early growing season sapflow ( Js) and leaf transpiration ( Tr) in Avicennia germinans at a latitudinal limit along the northern Gulf of Mexico (Louisiana, United States) under both flooded and drained states and used these data to scale vegetation water use responses in comparison with Spartina alterniflora. We discovered strong convergence when using either Js or Tr for determining individual tree water use, indicating tight connection between transpiration and xylem water movement in small Avicennia trees. When Tr data were combined with leaf area indices for the region with the use of three separate approaches, we determined that Avicennia stands use approximately 1·0-1·3 mm d-1 less water than Spartina marsh. Differences were only significant with the use of two of the three approaches, but are suggestive of net conservation of water as Avicennia expands into Spartina marshes at this location. Average Js for Avicennia trees was not influenced by flooding, but maximum Js was greater when sites were flooded. Avicennia and Spartina closest to open water (shoreline) used more water than interior locations of the same assemblages by an average of 1·3 mm d−1. Lower water use by Avicennia may indicate a greater overall resilience to drought relative to Spartina, such that aperiodic drought may interact with warmer winter temperatures to facilitate expansion of Avicennia in some years. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Aluminum (Al) accumulation and long-distance transport in oil tea (Camellia oleifera Abel.), known to be an Al accumulator, was investigated. The average Al concentration in the embryo of oil tea seeds was 389 mg Al kg−1 dry weight, which was higher than seeds of other Al accumulators. By partially suppressing leaf transpiration in the field, Al accumulation in leaves was depressed, which clarified the importance of xylem transport to Al accumulation in leaves. However, the effects of xylem transport alone could not sufficiently explain the high Al accumulation in the seasons when the leaf transpiration is weak, which hints the necessity of phloem transport working. Aluminum content in phloem exudates of barks provides another evidence of phloem transport. Images from scanning electron microscopy and energy-dispersive analysis also showed that Al was present in the phloem of oil tea petioles. Aluminum in oil tea could also be redistributed: higher concentrations of Al were found in leaves when Al was supplied to a different leaf of the same plant. In addition, Al was present in newly emerging roots of oil tea seedlings in which all original roots were excised prior to treatment, and a positive correlation existed between Al content in the newly formed roots and that in the leaves. The results using the empty seed coat technique showed that Al unloading via the phloem occurred during seed development. In conclusion, the results demonstrated that Al could be redistributed between leaves, from seeds to leaves, leaves to roots and leaves to seeds, which indicates that Al can be transported via the phloem in oil tea. [ABSTRACT FROM AUTHOR]

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Mountain peatlands in the temperate regions represent a small proportion of the global peatland resource, but play a unique, although less recognized role in the regional water and biogeochemical cycles. We conducted leaf and ecosystem CO exchange measurements during the growing period of 2008 to investigate the effects of vapor pressure deficit (VPD) and ground water level (WL) on leaf gas exchange of two dominant herbaceous species, Molinia caerulea (L.) and Carex nigra (L.) in a mountain peatland. Implications of the leaf-level responses for net ecosystem CO exchange (NEE) were examined. Fluctuations in WL influenced soil water content (SWC) within the top 5 cm of the peat profile. Although midday leaf water potential during the day (Ψ) was positively correlated ( P < 0.001) with SWC in the 5 cm peat profile, there was no direct relationship between WL and plant water relations parameters. VPD and stomatal conductance (gs) were negatively correlated at VPD >1 kPa regardless of the current WL status. Stomatal conductance was positively correlated with leaf assimilation (A) and root-shoot hydraulic conductance (K). A decline in NEE during summer was attributed to stomatal closure due to high VPD and low light utilization efficiency (α) of the vegetation. Ecosystem respiration (R) was positively correlated with peat temperature at 10 cm depth. Our results suggest that increases in VPD, as a possible scenario of climate change, would lower the photosynthetic capacity of the herbaceous peatland vegetation, despite the high WL, and hence lower the potential of such peatlands as sinks for atmospheric CO. [ABSTRACT FROM AUTHOR]

Summary: Arid and semi-arid ecosystems represent a dynamic but poorly understood component of global carbon, water, and energy cycles. We studied a semi-arid mountain big sagebrush (Artemisia tridentata var. vaseyana; hereafter, “sagebrush”) dominated ecosystem to quantify the (1) relative control of surface (0–15cm) versus deep (15–45cm) soil moisture on leaf transpiration (EL ) and stomatal conductance (gS ); (2) response of EL and gS to light and soil and atmospheric drought; and (3) physiological mechanisms underlying these responses. The physiological mechanisms were tested using a simple plant hydraulic model for gS based on homeostatic regulation of minimum leaf water potential (ΨLmin ) that was originally developed for trees. Our results showed that a combination of atmospheric and surface soil drought controlled EL , whereas gS was mainly driven by atmospheric drought. Sagebrush displayed greater reference conductance [gS @1kPa vapor pressure deficit (D), gSR ] and greater sensitivity (−m) of gS to D than mesic trees, reflecting the high average light intensity within the shrub canopy. The slope of −m/gSR was similar to mesic trees (∼0.6), indicating an isohydric regulation of ΨLmin , but different than previously published values for semi-arid shrubs (∼0.4). Isohydric behavior of sagebrush indicates that well-known forest ecosystem models with greater gSR and −m can be used for modeling water, energy and carbon cycles from sagebrush and similar ecosystems. [ABSTRACT FROM AUTHOR]

The root respiration rate often shows an exponential or a linear relationship with temperature under laboratory conditions. However, under intact conditions in the field, the root respiration rates of some tree species decreased around midday despite an increment of the root temperature (Bekku et al. ). To clarify the cause of midday depression, we examined the relationships between the intact root respiration and parameters of leaf gas exchange through the simultaneous field measurement of the gas exchange in the leaf and root of Quercus crispula and Chamaecyparis obtusa, which are canopy trees. There were no significant relationships between the root respiration rates ( R) and the parameters of leaf gas exchange in the field. However, in C. obtusa, the relationships between R and the transpiration rates ( E) at 1 h before the measurement of R were fitted by logarithmic function with a determination coefficient of 0.60-0.89. In the light-manipulation experiments using saplings, R had significant positive correlations with E at 20 min before the measurement of R, root temperature ( T), and the photosynthesis ( P) at 20 min before the measurement of R. We examined which factor, P or E, affects the root respiration rate through a manipulation experiment using a growth chamber regulating the ambient CO concentration and relative humidity independently under constant air temperature and photosynthetic photon flux density. As a result, the root respiration rates changed corresponding to E and not P. These results suggest that the root respiration rate of trees changes significantly in the daytime and is affected by the leaf transpiration rate as well as the temperature. [ABSTRACT FROM AUTHOR]

Calcium (Ca) uptake into fruit and leaves is dependent on xylemic water movement, and hence presumably driven by transpiration and growth. High leaf transpiration is thought to restrict Ca movement to low-transpiring tomato fruit, which may increase fruit susceptibility to the Ca-deficiency disorder, blossom end rot (BER). The objective of this study was to analyse the effect of reduced leaf transpiration in abscisic acid (ABA)-treated plants on fruit and leaf Ca uptake and BER development. Tomato cultivars Ace 55 (Vf) and AB2 were grown in a greenhouse environment under Ca-deficit conditions and plants were treated weekly after pollination with water (control) or 500 mg l−1 ABA. BER incidence was completely prevented in the ABA-treated plants and reached values of 30–45% in the water-treated controls. ABA-treated plants had higher stem water potential, lower leaf stomatal conductance, and lower whole-plant water loss than water-treated plants. ABA treatment increased total tissue and apoplastic water-soluble Ca concentrations in the fruit, and decreased Ca concentrations in leaves. In ABA-treated plants, fruit had a higher number of Safranin-O-stained xylem vessels at early stages of growth and development. ABA treatment reduced the phloem/xylem ratio of fruit sap uptake. The results indicate that ABA prevents BER development by increasing fruit Ca uptake, possibly by a combination of whole-plant and fruit-specific mechanisms. [ABSTRACT FROM PUBLISHER]

Abstract: The aim of this work was to study the association between leaf anatomical characteristics and response to short-term drought stress in Ziziphus mauritiana Lamk. Six Z. mauritiana cultivars (Seb, Gola, Umran, Keitly, Q-29 and B-5/4) under field conditions in Israel''s Negev desert were studied. Width of palisade mesophyll, spongy mesophyll and epidermis, xylem number and diameter in mid-vein were investigated with light microscopy. Short-term (3 weeks) drought stress tolerance was evaluated by monitoring plant response (leaf transpiration, diffusive resistance, chlorophyll fluorescence, leaf water potential and leaf relative water content). Greater epidermis and mesophyll widths and xylem diameters and densities were associated with increased tolerance to short-term water deficit expressed by preliminary wilting symptoms and proportional differences between initial and final physiological parameters. Significantly larger differences were found in Keitly, Umran and B-5/4 than in Seb, Gola and Q-29, indicating that the former cultivars are more sensitive to drought stress. Our results indicate that tolerance in descending order was Seb, Q-29, Gola, B-5/4, Keitly and finally Umran. The existence of an association between anatomical characteristics and short-term drought stress tolerance based on physiological responses is suggested. [Copyright &y& Elsevier]

Studies concerning factors involved in the adaptation of micropropagated plants to ex vitro conditions are indispensable to define which procedures should be used during the acclimatization phase. The objective of this research was to evaluate the presence of stomata and epicuticular wax on water loss control in micropropagated banana plants. For 24 days axillary buds were rooted in MS medium supplemented with NAA (1mg L-1) and agar (6g L-1), and afterwards the plantlets were acclimatized for 120 days. The treatments consisted of the evaluation of in vitro leaves and at different acclimatization stages, as follows: T1 - leaves of plants at the end of the in vitro rooting phase T2 - persistent leaves of plants after 30 days of acclimatization; T3 - new leaves from plants after 30 days of acclimatization (transition leaves); T4 - transition leaves from plants after 60 days of acclimatization; T5 and T6 - new leaves from plants after 60 and 120 days of acclimatization, respectively. Data regarding stomatal density, relative water content and presence of epicuticular wax were also evaluated. It was verified that new leaves from plants rooted in vitro under mixotrophic condition presented height stomatal density and hence a reduced control of water loss. The reduced transpiration of leaves formed during the acclimatization phase can be attributed to the small number of stomata per unit of leaf area associated to the largest capacity of these in restricting water loss, and the presence of epicuticular wax. [ABSTRACT FROM AUTHOR]

Abstract: The process of photosynthesis is facilitated by pores on the leaf surface called stomata. When a particular stoma is open, CO2 is absorbed through its aperture, but H2O is also lost due to evaporation. Thus a plant will seek a stomatal aperture that balances its need for CO2 with its aversion to H2O loss. In order to visualize a particular leaf’s stomatal aperture distribution and how it changes with time, fluorescence data is collected at regular intervals as digital images, resulting in a video sequence. It has been observed that stomatal apertures are often synchronized into spatially extended patches. In order objectively to analyze this phenomenon we have developed a technique to isolate patches via a three-dimensional PDE-based segmentation method. The resulting segmented data is then collapsed to a vector valued time series of much smaller dimension with a hybrid PCA-Archetypal Analysis approach. This allows for a unique interpretation of the data in terms of statistical measures of the motions of representative patches. The technique is illustrated with a data-set from a particularly complicated regime collected by the Complexity and Stomatal Behavior research lab at Utah State University. [Copyright &y& Elsevier]