Changes In Leaf Water Status Research Articles

Assessing grapevine water status through fusion of hyperspectral imaging and 3D point clouds

Mild to moderate and timely water deficit is desirable in grape production to optimize fruit quality for winemaking. It is crucial to develop robust and rapid approaches to assess grapevine water stress for scheduling deficit irrigation. Hyperspectral imaging (HSI) has the potential to detect changes in leaf water status, but the robustness and accuracy are restricted in field applications. The varied leaf orientations can significantly affect how light interacts with the plant, ultimately influencing the reflectance properties. This study focused on developing an approach for detecting grapevine water status using HSI and 3D data. Leaf orientation parameters derived from 3D point clouds were integrated with spectral signatures to address the spectral variance caused by variations in leaf orientation. A water status assessment model was developed based on multiblock partial least squares (MBPLS) to estimate midday leaf water potential (ΨL) using spectral signatures and leaf orientation parameters. HSI and 3D point clouds of selected leaves were captured simultaneously in a vineyard during the 2021 growing season, and ΨL was measured as the ground truth to assess the model performance. Mean spectral reflectance was derived from the hyperspectral images, while leaf orientation parameters were extracted from 3D point cloud data. The dataset was split randomly into 70% training/calibration and 30% test datasets. The test result shows that the model estimated the ΨL with R2 = 0.89, RMSE=0.12 MPa and MAE=0.09 MPa. The leaf orientation parameters derived from 3D point clouds had a contribution of 6.25% in estimating ΨL. Moreover, it acted as an enhancing component that explained the spectral variance caused by variations in leaf orientation and improved the interpretation of the underlying relationship between spectral reflectance and vine water status.

Estimating soil and grapevine water status using ground based hyperspectral imaging under diffused lighting conditions: Addressing the effect of lighting variability in vineyards

A timely and appropriate level of water deficit is desirable in wine grape production to optimize fruit quality for winemaking. Thus, it is crucial to find a robust and rapid method to assess grapevine water stress in real time. Hyperspectral imaging (HSI) has the potential to detect changes in leaf water status, but the robustness and accuracy are limited in field applications. This study focused on developing ground based approaches for detecting soil and grapevine water status using HSI obtained in diffused lighting conditions. During the 2021 growing season, leaf water potential (ΨL), stomatal conductance (gs) on the selected leaves and volumetric soil moisture (θv) in the root zone were measured as water status indicators. Spectral data from diffused and direct sunlight conditions were obtained to construct models to estimate plant and soil water status indicators. Partial least squares (PLS) regression models were individually developed to estimate ΨL, gs, and θv using spectra obtained from direct/diffused lighting conditions, respectively. The results indicated that the ΨL estimation model using spectral data from diffused lighting performed better than that obtained using direct sunlight, indicated by a higher R2 (0.89 vs. 0.82), a lower RMSE (0.12 vs. 0.15 MPa) and a lower MAE (0.10 vs. 0.11 MPa). The model developed for estimating θv using spectral data under diffused lighting achieved superior performance to the one in direct sunlight in terms of R2, RMSE and MAE (0.90 vs. 0.89 and 1.56 vs. 1.59 %, 1.26 vs. 1.29 %). These results demonstrated that spectral data obtained under diffused lighting can improve model performance by providing a more uniform illumination. Ground based HSI was capable of high-resolution sensing of grapevine water status by estimating ΨL and gs and map variability within canopies.

Stomata: the holey grail of plant evolution

Stomata: the holey grail of plant evolution

Misleading conclusions from exogenous ABA application: a cautionary tale about the evolution of stomatal responses to changes in leaf water status

ABSTRACTStomatal responses to changes in leaf water status are critical for minimizing excessive water loss during soil drought. A major debate has surrounded the evolution of stomatal responses to water status and this debate has particularly focused on the evolution of the regulatory role of the drought hormone abscisic acid (ABA). Studies relying on the application of high levels of exogenous ABA have occasionally concluded that all stomata respond to ABA and that stomatal regulation in response to this hormone has not evolved over the past 450 million years. In contrast, studies which have investigated stomatal function in intact plants, as well as the role of endogenous ABA in regulating stomatal aperture, have found major evolutionary transitions in the functional regulation of stomata across land plant lineages. We show that endogenous ABA plays no role in closing the stomata of the fern Nephrolepis exaltata during natural soil drought, in contrast to a recent finding using isolated epidermis and exceptionally high levels of exogenous ABA. We conclude that stomatal behavior in intact plants has evolved over time, and may have shaped the evolutionary and ecological success of successive land plant lineages.

Potential of the existing and novel spectral reflectance indices for estimating the leaf water status and grain yield of spring wheat exposed to different irrigation rates

Hyperspectral sensing technique can provide an exact and expeditious manner for effective management of deficit irrigation through assessment of changes in plant water status in a large scale and real-time. This hypothesis was tested in this study using the hyperspectral signatures of the canopy in the visible- (VIS), near- (NIR), and shortwave-infrared (SWIR) to estimate and predict the leaf water status, measured here in terms of leaf water potential (LWP), relative water content (RWC), and equivalent water thickness (EWT), and grain yield (GY) of wheat cultivars exposed to 1.00, 0.75, and 0.50 of the estimated evapotranspiration (ETc). Results showed that the three parameters of leaf water status exhibited strong correlations with GY under 0.75 (except LWP) and 0.50 ETc treatments. This indicates that these parameters can be used as early indicators for management of deficit irrigation. Based on the relationships between these four phenotypic parameters and original canopy spectral reflectance within 350–2500 nm, the sensitive spectral wavelengths that exhibited strong correlations with all parameters existed mainly within the NIR and SWIR regions, with peak-wavelengths around 351, 518, and 687 nm in the VIS, 762, 974, 1100, and 1240 nm in the NIR, and 1392, 1515, 1930, and 2273 nm in the SWIR regions. These peak-wavelengths were used to build new two- and three-band normalized spectral reflectance indices (NDSIs). The NDSIs that combine NIR and VIS, NIR and NIR, SWIR and NIR, and SWIR and SWIR wavelengths were more effective for tracking changes in leaf water status and GY than those that combine only VIS wavelengths. The high fit between the observed and predicted values for phenotypic parameters based on twelve newly developed and published NDSIs indicates that the most recently developed NDSI models were more precise and accurate, and thus could be used for monitoring the changes in leaf water status and wheat production caused by deficit irrigation. The performance of partial least square regression (PLSR) based on either eleven wavelengths or different NDSIs as a predictive approach was the same and sometimes better than the individual NDSIs for assessment of phenotypic parameters. The results of spectral reflectance data and PLSR tools can serve as rapid and non-destructive alternative approaches for monitoring the water status and wheat production, and can be used to develop certain spectral indices for management of deficit irrigation in arid regions.

Hydraulics Regulate Stomatal Responses to Changes in Leaf Water Status in the Fern Athyrium filix-femina.

Stomatal responses to changes in leaf water status are important for the diurnal regulation of gas exchange and the survival of plants during drought. These stomatal responses in angiosperm species are well characterized, yet in species of nonseed plants, an ongoing debate surrounds the role of metabolism, particularly the role of the hormone abscisic acid (ABA), in functionally regulating stomatal responses to changes in leaf water status. Here, we measured the stomatal response to changes in vapor pressure difference (VPD) in two natural forms of the fern species Athyrium filix-femina, recently suggested to have stomata that are regulated by ABA. The two forms measured had considerable differences in key hydraulic traits, including leaf hydraulic conductance and capacitance, as well as the kinetics of stomatal response to changes in VPD. In both forms, the stomatal responses to VPD could be accurately predicted by a dynamic, mechanistic model that assumes guard cell turgor changes in concert with leaf turgor in the light, and not via metabolic processes including the level of ABA. During drought, endogenous ABA did not play a role in stomatal closure, and exogenous ABA applied to live, intact leaves did not induce stomatal closure. Our results indicate that functional stomatal responses to changes in leaf water status in ferns are regulated by leaf hydraulics and not metabolism. With ferns being sister to seed plants, this result has implications for the evolutionary reconstruction of functional stomatal responses across vascular land plant lineages.

Grapevine leafroll disease alters leaf physiology but has little effect on plant cold hardiness.

Foliar sugar accumulation in grapevines with leafroll disease was correlated with lower photosynthesis, likely due to feedback inhibition. However, cold acclimation of dormant tissues remained unaffected by the virus status. Grapevine leafroll-associated viruses (GLRaV) contribute to losses in fruit yield and quality worldwide. Visually, leafroll disease symptoms appear similar to those associated with an imbalance in source/sink relations and a concomitant feedback inhibition of photosynthesis, which is often caused by an impasse in sugar translocation. In order to test this potential relationship and related physiological responses, leaf water status, gas exchange, non-structural carbohydrates, and dormant tissue cold hardiness were examined over 2years in healthy and GLRaV-3-infected, field-grown Merlot grapevines. Diurnal and seasonal changes in leaf water status and gas exchange were dominated by variations in water availability, temperature, and leaf age, while GLRaV-3 infection contributed less to the overall variation. By contrast, foliar carbohydrates increased markedly in infected plants, with starch accumulating early in the growing season, followed by soluble sugar accumulation, leaf reddening, and declining gas exchange. Photosynthesis correlated negatively with leaf sugar content. However, dormant-season cold hardiness of buds and cane vascular tissues was similar in healthy and infected vines. These findings support the idea that visible symptoms of grapevine leafroll disease are a consequence of carbohydrate accumulation which, in turn, may lead to feedback inhibition of photosynthesis. In addition, this study provided evidence that GLRaV-3 infection is unlikely to alter the susceptibility to moderate water deficit and winter damage in mature Merlot grapevines.

Abscisic acid (ABA) and key proteins in its perception and signaling pathways are ancient, but their roles have changed through time

ABSTRACTHomologs of the Arabidopsis core abscisic acid (ABA) signaling component OPEN STOMATA1 (OST1) are best known for their role in closing stomata in angiosperm species. We recently characterized a fern OST1 homolog, GAMETOPHYTES ABA INSENSITIVE ON ANTHERDIOGEN 1 (GAIA1), which is not required for stomatal closure in ferns, consistent with physiologic evidence that shows the stomata of these plants respond passively to changes in leaf water status. Instead, gaia1 mutants reveal a critical role in ABA signaling for spore dormancy and sex determination, in a system regulated by antagonism between ABA and the gibberellin (GA)-derived fern hormone antheridiogen (ACE). ABA and key proteins, including ABA receptors from the PYR/PYL/RCAR family and negative regulators of ABA-signaling from Group A of the type-2C protein phosphatases (PP2Cs), in addition to OST1 homologs, can be found in all terrestrial land plant lineages, ranging from liverworts that lack stomata, to angiosperms. As land plants have evolved and diversified over the past 450 million years, so too have the roles of this important plant hormone and the genes involved in its signaling and perception.

What are the evolutionary origins of stomatal responses to abscisic acid in land plants?

The evolution of active stomatal closure in response to leaf water deficit, mediated by the hormone abscisic acid (ABA), has been the subject of recent debate. Two different models for the timing of the evolution of this response recur in the literature. A single-step model for stomatal control suggests that stomata evolved active, ABA-mediated control of stomatal aperture, when these structures first appeared, prior to the divergence of bryophyte and vascular plant lineages. In contrast, a gradualistic model for stomatal control proposes that the most basal vascular plant stomata responded passively to changes in leaf water status. This model suggests that active ABA-driven mechanisms for stomatal responses to water status instead evolved after the divergence of seed plants, culminating in the complex, ABA-mediated responses observed in modern angiosperms. Here we review the findings that form the basis for these two models, including recent work that provides critical molecular insights into resolving this intriguing debate, and find strong evidence to support a gradualistic model for stomatal evolution.

Photosynthesis impairments precede noticeable changes in leaf water status of mango plants infected by Ceratocystis fimbriata

Mango wilt, caused by Ceratocystis fimbriata, is a disease of great economic importance in mango production. Considering that the physiological effects of this vascular disease are not fully characterized, this study aimed to investigate some alterations in mango leaves from cultivars Uba and Tommy Atkins, respectively, resistant and moderately resistant to mango wilt. The relationships between relative lesion indices (upward relative lesion length (URLL), the downward relative lesion length (DRLL) and the radial fungal colonization (RFC)) and water relations and gas exchange and chlorophyll a fluorescence parameters were evaluated at 10, 20 and 30 days after inoculation. The foliar concentrations of lipid peroxidation, total pigments and total free amino acids and proline were also determined. The URLL, DRLL and RFC increased overtime in both Uba and Tommy Atkins cultivars, but reached the greatest values for cv. Tommy Atkins. Although cultivars did not present contrasting results for most of the evaluated parameters, the relative changes between inoculated and non-inoculated plants of each cultivar were more disparate in plants from cv. Tommy Atkins. There were decreases of 55, 73, 65 and 22 %, respectively, for net carbon assimilation rate (A), stomatal conductance to water vapor (g s), transpiration rate (E) and internal-to-ambient CO2 concentration ratio (C i/C a) for inoculated plants from cv. Tommy Atkins in comparison to the non-inoculated plants. For inoculated plants from cv. Uba, there were decreases of 25, 41 and 36 % for A, g s and E while C i/C a decreased by 17 % in relation to the non-inoculated plants. Inoculated plants of cvs. Tommy Atkins and Uba showed pronounced reductions for midday leaf water potential and apparent hydraulic conductance relative to the control. Inoculated plants from cv. Uba showed values of predawn leaf water potential that were 25 % higher in comparison to inoculated plants from cv. Tommy Atkins. In addition, decreases in total chlorophyll concentration as well as increases in free amino acids and lipid peroxidation occurred for inoculated plants from cv. Tommy Atkins.

Feedback regulation of irrigation via soil moisture monitoring and its effects on plant growth and physiology

Currently, 80% of the world's available fresh water resource is used for irrigated agriculture. Growers usually try to ensure profitable crop production rather than considering possible environmental impacts, which can lead to misjudgement of the plant's actual needs and result in under- or over-irrigation. To understand how manual watering influences soil water status, soil moisture sensors were deployed in a representative commercial nursery. By automatically scheduling irrigation according to soil moisture thresholds, this work tries to understand the effects of deficit irrigation (under-irrigation - applying less than full water requirements) on possible growth regulation through changes in leaf water status, gas exchange and plant hormone balance. Tomatoes (Solanum lycopersicum Mill. 'Ailsa Craig') were grown in a peat-based substrate in a controlled environment, and exposed to different irrigation treatments by varying the number of drippers in the pot (1 water deficit, 2 control). Hand-watering in a commercial nursery resulted in significant variation in soil water content that may compromise crop uniformity and quality. In contrast, feedback regulation of irrigation via soil moisture monitoring provides a useful tool to water plants according to their actual water needs, with significantly less variation in soil moisture. Under-irrigating containerised tomato plants significantly reduced evapotranspiration, crop fresh weight, height and leaf area and decreased leaf water potential and stomatal conductance. Although foliar concentrations of the phytohormone abscisic acid (ABA) varied throughout the treatment period, ethylene emission from shoot increased. However, the role of these plant hormones during water deficit requires further experimentation using mutants deficient in these hormones. Although deficit irrigation as applied here limited tomato vegetative growth, further long-term experiments (that measure fruit yield) are needed to evaluate whether automatic irrigation scheduling can be used as a water-saving technique.

Stomatal dynamics are limited by leaf hydraulics in ferns and conifers: results from simultaneous measurements of liquid and vapour fluxes in leaves.

Stomatal responsiveness to vapour pressure deficit (VPD) results in continuous regulation of daytime gas-exchange directly influencing leaf water status and carbon gain. Current models can reasonably predict steady-state stomatal conductance (gs ) to changes in VPD but the gs dynamics between steady-states are poorly known. Here, we used a diverse sample of conifers and ferns to show that leaf hydraulic architecture, in particular leaf capacitance, has a major role in determining the gs response time to perturbations in VPD. By using simultaneous measurements of liquid and vapour fluxes into and out of leaves, the in situ fluctuations in leaf water balance were calculated and appeared to be closely tracked by changes in gs thus supporting a passive model of stomatal control. Indeed, good agreement was found between observed and predicted gs when using a hydropassive model based on hydraulic traits. We contend that a simple passive hydraulic control of stomata in response to changes in leaf water status provides for efficient stomatal responses to VPD in ferns and conifers, leading to closure rates as fast or faster than those seen in most angiosperms.

Physiological and biochemical responses to partial root-zone drying of three grape cultivars

Physiological and biochemical responses of three grapevine cultivars (Vitis Vinifera L., ‘Pinot Noir’, Vitis Labrusca Bailey, ‘Concord’ and French American hybrid (JS 23.416 × Gewurztraminer, ‘Traminette’) to partial root-zone drying (PRD) were investigated in potted plants under controlled environmental conditions. The treatments were either full irrigation (FI) where both sides of the root system were irrigated daily to pot capacity (the controls), or PRD where irrigation was withheld on the dried side for 14 days while the wet side was irrigated as FI. PRD and FI treatments did not exhibit any significant differences in leaf water potential (ΨL) or photosynthetic rate (A). Stomatal conductance (gs) was more sensitive to PRD than photosynthesis. PRD reduced stomatal conductance by 41, 28 and 47 % in Concord, Pinot Noir, and Traminette, respectively, compared to the controls. This resulted in increased water use efficiency (WUE) by 14, 76 and 67 % in Concord, Pinot Noir, and Traminette, respectively. ABA concentration in the PRD-dry side treatment was higher (P > 0.001) than both PRD-wet side and the full irrigation treatment. Shoot growth rate of PRD-treated vines was reduced by 36, 26 and 51 % in Concord, Pinot Noir, and Traminette, respectively, compared to fully irrigated vines. The inhibition of gs and shoot growth that occurred independently of changes in leaf water status could be due to enhanced accumulation of ABA in roots and shoots, which probably maintained a high water status by reducing water loss under PRD conditions.

Disruption of mycorrhizal extraradical mycelium and changes in leaf water status and soil aggregate stability in rootbox-grown trifoliate orange.

Arbuscular mycorrhizas possess well developed extraradical mycelium (ERM) network that enlarge the surrounding soil for better acquisition of water and nutrients, besides soil aggregation. Distinction in ERM functioning was studied under a rootbox system, which consisted of root+hyphae and root-free hyphae compartments separated by 37-μm nylon mesh with an air gap. Trifoliate orange (Poncirus trifoliata) seedlings were inoculated with Funneliformis mosseae in root+hyphae compartment, and the ERM network was established between the two compartments. The ERM network of air gap was disrupted before 8 h of the harvest (one time disruption) or multiple disruptions during seedlings acclimation. Our results showed that mycorrhizal inoculation induced a significant increase in growth (plant height, stem diameter, and leaf, stem, and root biomass) and physiological characters (leaf relative water content, leaf water potential, and transpiration rate), irrespective of ERM status. Easily-extractable glomalin-related soil protein (EE-GRSP) and total GRSP (T-GRSP) concentration and mean weight diameter (MWD, an indicator of soil aggregate stability) were significantly higher in mycorrhizosphere of root+hyphae and root-free hyphae compartments than non-mycorrhizosphere. One time disruption of ERM network did not influence plant growth and soil properties but only notably decreased leaf water. Periodical disruption of ERM network at weekly interval markedly inhibited the mycorrhizal roles on plant growth, leaf water, GRSP production, and MWD in root+hyphae and hyphae chambers. EE-GRSP was the most responsive GRSP fraction to changes in leaf water and MWD under root+hyphae and hyphae conditions. It suggests that effect of peridical disruption of ERM network was more impactful than one-time disruption of ERM network with regard to leaf water, plant growth, and aggregate stability responses, thereby, implying ERM network aided in developing the host plant metabolically more active.

The evolution of mechanisms driving the stomatal response to vapor pressure deficit.

Stomatal responses to vapor pressure deficit (VPD) are a principal means by which vascular land plants regulate daytime transpiration. While much work has focused on characterizing and modeling this response, there remains no consensus as to the mechanism that drives it. Explanations range from passive regulation by leaf hydration to biochemical regulation by the phytohormone abscisic acid (ABA). We monitored ABA levels, leaf gas exchange, and water status in a diversity of vascular land plants exposed to a symmetrical, mild transition in VPD. The stomata in basal lineages of vascular plants, including gymnosperms, appeared to respond passively to changes in leaf water status induced by VPD perturbation, with minimal changes in foliar ABA levels and no hysteresis in stomatal action. In contrast, foliar ABA appeared to drive the stomatal response to VPD in our angiosperm samples. Increased foliar ABA level at high VPD in angiosperm species resulted in hysteresis in the recovery of stomatal conductance; this was most pronounced in herbaceous species. Increased levels of ABA in the leaf epidermis were found to originate from sites of synthesis in other parts of the leaf rather than from the guard cells themselves. The transition from a passive regulation to ABA regulation of the stomatal response to VPD in the earliest angiosperms is likely to have had critical implications for the ecological success of this lineage.

Effect of rain shelters and drought on leaf water status and photosynthetic parameters in tomato

The present study explored the effect of rain shelter and drought on photosynthetic activity and changes in leaf water status. Tomatoes were grown in the trial plot located at Hohai University, China, in 2011 and 2012, and allotted to five treatments [80% field capacity under open field (T1, control) and rain shelter (T2), 70%, 60%, and 50% of T2 (T3, T4, and T5)]. The lowest sap flow rate and relative water content and the highest values for specific leaf area were obtained from plants in T5. T2 decreased the average net photosynthetic rate (PN) by 5.35% compared to the control, although there was no reduction in intercellular CO2 concentration and stomatal conductance. The average reduction of transpiration rate registered under rain shelters was only around 10.2% in both the years. The PN, maximum quantum yield of PSII photochemistry (Fv/Fm) and activity of the water-splitting complex on the donor side of the PSII (Fv/Fo) decreased with irrigation volume. Quenching analyses showed the development of a lower photochemical quenching (qP) in plants under rain shelters, accompanied by the development of a higher nonphotochemical quenching (qN). Drought-stressed tomato exhibited a decrease in qP parallel to an increase in qN.

Monitoring Plant Drought Stress Response Using Terahertz Time-Domain Spectroscopy

We present a novel measurement setup for monitoring changes in leaf water status using nondestructive terahertz time-domain spectroscopy (THz-TDS). Previous studies on a variety of plants showed the principal applicability of THz-TDS. In such setups, decreasing leaf water content directly correlates with increasing THz transmission. Our new system allows for continuous, nondestructive monitoring of the water status of multiple individual plants each at the same constant leaf position. It overcomes previous drawbacks, which were mainly due to the necessity of relocating the plants. Using needles of silver fir (Abies alba) seedlings as test subjects, we show that the transmission varies along the main axis of a single needle due to a variation in thickness. Therefore, the relocation of plants during the measuring period, which was necessary in the previous THz-TDS setups, should be avoided. Furthermore, we show a highly significant correlation between gravimetric water content and respective THz transmission. By monitoring the relative change in transmission, we were able to narrow down the permanent wilting point of the seedlings. Thus, we established groups of plants with well-defined levels of water stress that could not be detected visually. This opens up the possibility for a broad range of genetic and physiological experiments.

Physiological Responses of Jatropha to Drought Stress in Coastal Sandy Land Conditions

Normal 0 false false false IN X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Jatropha curcas L ., an important tropical biofuel crop, is reputed for its drought resistance, however, its ability to perform in dry conditions has still hardly been investigated. Changes in leaf water status, chlorophyll content, leaf surface temperature, stomatal conductance, proline and abcisic acid (ABA) content, transpiration and photosynthetic rate were studied in four Jatropha genotypes (IP-1A, IP-2M, Local superior and Yellow leaf) and subjected to drought stress in coastal sandy land conditions in Central Java, Indonesia. Drought stress significantly decreased the leaf water status, leaf chlorophyll content, stomatal conductance, transpiration and photosynthetic rate, and increased leaf temperature, proline and ABA content. Resistant genotypes (IP-1A and IP-2M) had significantly higher leaf water status, chlorophyll content and photosynthetic rate than susceptible genotypes (Local superior and Yellow leaf). There were no differences between the Jatropha genotypes on leaf temperature, stomatal conductance and transpiration rate. Normal 0 false false false IN X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Keywords: ABA, biofuel , photosynthetic rate, proline, stomata, water status

Photosynthetic response of Tempranillo grapevine to climate change scenarios

AbstractPhotosynthesis in C3 plants is CO2 limited and therefore any increase in Rubisco carboxylation substrate may increase net CO2 fixation, unless plants experience acclimation or other limitations. These aspects are largely unexplored in grapevine. Photosynthesis analysis was used to assess the stomatal, mesophyll, photochemical and biochemical contributions to the decreasing photosynthesis observed in Tempranillo grapevines (Vitis vinifera) from veraison to ripeness, modulated by CO2, temperature and water availability. Photosynthesis and photosystem II photochemistry decreased from veraison to ripeness. The elevated CO2 and temperature increased photosynthesis, but transiently, in both well irrigated (WI) and water‐stressed plants. Photosynthetic rates were maxima 1 week after the start of elevated CO2 and temperature treatments, but differences with treatments of ambient conditions disappeared with time. There were not marked changes in leaf water status, leaf chlorophyll or leaf protein that could limit photosynthesis at ripeness. Leaf total soluble sugars remained at ripeness as high as 2 weeks after the start of treatments. On the other hand, and as expected, CO2 diffusional limitations impaired photosynthesis in grapevine plants grown under water scarcity, stomatal and mesophyll conductances to CO2 decreased and in turn low chloroplastic CO2 concentrations limited photosynthetic CO2 fixation. In summary, photochemistry and photosynthesis from veraison to ripeness in Tempranillo grapevine were dominated by a developmental‐related decreasing trend that was only transiently influenced by elevated CO2 concentrations.

Changes in root system structure, leaf water potential and gas exchange of maize and triticale seedlings affected by soil compaction

The physiological reasons associated with differential sensitivity of C3 and C4 plant species to soil compaction stress are not well explained and understood. The responses of growth characteristics, changes in leaf water potential and gas exchange in maize and triticale to a different soil compaction were investigated. In the present study seedlings of triticale and maize, representative of C3 and C4 plants were subjected to low (L – 1.10gcm−3), moderate (M – 1.34gcm−3) and severe (S – 1.58gcm−3) soil compaction level. Distinct differences in distribution of roots in the soil profile were observed. Plants of treatments M or S in comparison to treatment L, showed a decrease in leaf number, dry mass of stem, leaves and roots, and an increase in the shoot to root ratio. A drastic decrease in root biomass in M and S treatments in the soil profile on depth from 15 to 40cm was observed. Any level of soil compaction did not influence the number of seminal and seminal-adventitious roots but decreased their length. The number and total length of nodal roots decreased with compaction. Changes of growth traits in M and S treatments in comparison to the L were greater for maize than for triticale and were accompanied by daily changes in water potential (ψ) and gas exchange parameters (PN, E, gs). Differences between M and S treatments in daily changes in ψ for maize were in most cases statistically insignificant, whereas for triticale, they were statistically significant. Differences in the responses of maize and triticale to soil compaction were found in PN, E and gs in particular for the measurements taken at 12:00 and 16:00. The highest correlation coefficients were obtained for the relationship between leaf water potential and stomatal conductance, both for maize and triticale, which indicates the close association between stomata behavior and changes in leaf water status.