Nutritional management and physiological responses of Atriplex nummularia Lindl. on the improvement of phytoextraction in salt-affected soil.

Soil salinity is a significant abiotic stress and poses risks to environmental sustainability. Thus, the improvement of the time for recovering the salt-affect soil is crucial for the phytoextraction process using halophytes plants, especially regarding on nutritional management. We evaluated the responses of Atriplex nummularia Lindl. to nitrogen (N) and phosphorus (P) under different salinity levels. The treatments comprised doses of N (N1 = 80 kg ha-1) and P (P1 = 60 kg ha-1): (1) without N and P (N0P0) (control); (2) with N and without P (N1P0); (3) without N and with P (N0P1); and (4) with N and P (N1P1) and five levels of electrical conductivity from irrigation water: 0.08, 1.7, 4.8, 8.6, and 12.5 dS m-1. The. We evaluated dry biomass of leaves, stems, and roots 93 days after transplantation. We also assessed the leaf and osmotic water potential, the osmotic adjustment, and the nutrient contents (N, P, Na, and K). N application increased 22.3, 17.8, and 32.8% the leaf biomass, stem biomass, and osmotic adjustment, respectively; and consequently, boosts Na extraction in 27.8%. Thus, the time of the phytoextraction process can be improved with N fertilizer at a rate of 80 kg ha-1.

Very few studies have investigated the nutrient dynamics responses in Atriplex species in salt-affected soils; thus, this study represents a novelty. We tested the management of nitrogen (N) and phosphate (P) fertilizers to increase crop yield and optimize the phytoextraction process in salt-affected soils. We believe our results contribute to the improvement of the knowledge of this relevant topic, mainly in terms of the recovery of areas degraded by salinity. There is a paucity of studies associating salinity and nutritional management of soils worldwide.

Sweet Cherry Plants Prioritize Their Response to Cope with Summer Drought, Overshadowing the Defense Response to Pseudomonas syringae pv. syringae.

Disease severity and drought due to climate change present significant challenges to orchard productivity. This study examines the effects of spring inoculation with Pseudomonas syringae pv. syringae (Pss) on sweet cherry plants, cvs. Bing and Santina with varying defense responses, assessing plant growth, physiological variables (water potential, gas exchange, and plant hydraulic conductance), and the levels of abscisic acid (ABA) and salicylic acid (SA) under two summer irrigation levels. Pss inoculation elicited a more pronounced response in 'Santina' compared to 'Bing' at 14 days post-inoculation (dpi), and those plants inoculated with Pss exhibited a slower leaf growth and reduced transpiration compared to control plants during 60 dpi. During differential irrigations, leaf area was reduced 14% and 44% in Pss inoculated plants of 'Bing' and 'Santina' respectively, under well-watered (WW) conditions, without changes in plant water status or gas exchange. Conversely, water-deficit (WD) conditions led to gas exchange limitations and a 43% decrease in plant biomass compared to that under WW conditions, with no differences between inoculation treatments. ABA levels were lower under WW than under WD at 90 dpi, while SA levels were significantly higher in Pss-inoculated plants under WW conditions. These findings underscore the influence on plant growth during summer in sweet cherry cultivars that showed a differential response to Pss inoculations and how the relationship between ABA and SA changes in plant drought level responses.

Brief windows with more favorable atmospheric conditions explain patterns of Polylepis reticulata tree water use in a high-altitude Andean forest.

Polylepis trees occur throughout the Andean mountain region, and it is the tree genus that grows at the highest elevation worldwide. In the humid Andes where moisture is rarely limiting, Polylepis trees must adapt to extreme environmental conditions, especially rapid fluctuations in temperature, ultraviolet radiation and vapor pressure deficit (VPD). However, Polylepis' water-use patterns remain largely unknown despite the importance of understanding their response to microclimate variation to determine their capacity to maintain resilience under future environmental change. We conducted a study in a Polylepis reticulata Kunth forest in the Ecuadorian Andes to evaluate its tree water-use dynamics and to identify the main environmental drivers of transpiration. Tree sap flow was monitored simultaneously with soil volumetric water content (VWC) and microclimate during 2 years for trees growing in forest edge and interior locations. We found that sap flow was primarily controlled by VPD and that VWC exerted a secondary role in driving sap flow dynamics. The highest values for sap flow rates were found when VPD > 0.15 kPa and VCW < 0.73 cm3 cm-3, but these threshold conditions only occurred during brief periods of time and were only found in 11% of our measurements. Moreover, these brief windows of more favorable conditions occurred more frequently in forest edge compared with forest interior locations, resulting in edge trees maintaining 46% higher sap flow compared with interior trees. Our results also suggest that P. reticulata has a low stomatal control of transpiration, as the sap flow did not decline with increasing VPD. This research provides valuable information about the potential impacts of projected future increases in VPD due to climate change on P. reticulata water-use dynamics, which include higher sap flow rates leading to greater transpirational water loss due to this species' poor stomatal control.

Irrigation Strategies with Controlled Water Deficit in Two Production Cycles of Cotton.

Water scarcity is one of the main abiotic factors that limit agricultural production. In this sense, the identification of genotypes tolerant to water deficit associated with irrigation management strategies is extremely important. In this context, the objective of this study was to evaluate the morphology, production, water consumption, and water use efficiency of colored fiber cotton genotypes submitted to irrigation strategies with a water deficit in the phenological phases. Two experiments were conducted in succession. In the first experiment, a randomized block design was used in a 3 × 7 factorial scheme, corresponding to three colored cotton genotypes (BRS Rubi, BRS Jade, and BRS Safira) in seven irrigation management strategies with 40% of the real evapotranspiration (ETr) varying the phenological stages. In the second experiment, the same design was used in a 3 × 10 factorial arrangement (genotypes × irrigation management strategies). The water deficit in the vegetative phase can be used in the first year of cotton cultivation. Among the genotypes, 'BRS Jade' is the most tolerant to water deficit in terms of phytomass accumulation and fiber production.

Monitoring Energy Balance, Turbulent Flux Partitioning, Evapotranspiration and Biophysical Parameters of Nopalea cochenillifera (Cactaceae) in the Brazilian Semi-Arid Environment.

The in-situ quantification of turbulent flux and evapotranspiration (ET) is necessary to monitor crop performance in stressful environments. Although cacti can withstand stressful conditions, plant responses and plant-environment interactions remain unclear. Hence, the objective of our study was to investigate the interannual and seasonal behaviour of components of the surface energy balance, environmental conditions, morphophysiological parameters, biomass yield and water relations in a crop of Nopalea cochenillifera in the semi-arid region of Brazil. The data were collected from a micrometeorological tower between 2015 and 2017. The results demonstrate that net radiation was significantly higher during the wet season. Latent heat flux was not significant between the wet season and dry season. During the dry-wet transition season in particular, sensible heat flux was higher than during the other seasons. We observed a large decline in soil heat flux during the wet season. There was no difference in ET during the wet or dry seasons; however, there was a 40% reduction during the dry-wet transition. The wet seasons and wet-dry transition showed the lowest Evaporative Stress Index. The plants showed high cladode water content and biomass during the evaluation period. In conclusion, these findings indicate high rates of growth, high biomass and a high cladode water content and explain the response of the cactus regarding energy partitioning and ET.

Contrasting leaf intercellular space development in sorghum and maize modulates different tolerance capacity to water limitation.

The objective of this study was to evaluate the relationship between intercellular spaces and leaf gas exchange and the effect of total intercellular space on the growth of maize and sorghum under water restriction. The experiments were conducted in a greenhouse in a 2 × 3 factorial arrangement (two plant types and three water conditions: field capacity (FC = 100%), 75%FC, and 50%FC) with 10 replicates. The lack of water was a limiting factor for maize because it showed reductions in leaf area, leaf thickness, biomass, and gas exchange parameters, while sorghum remained unchanged, maintaining its water-use efficiency. This maintenance was correlated with the growth of intercellular spaces in sorghum leaves because the increased internal volume led to better CO2 control and prevented excessive water loss under drought stress. In addition, sorghum had more stomata than maize. These characteristics contributed to the drought tolerance of sorghum, while maize could not make the same adjustments. Therefore, changes in intercellular spaces promoted adjustments to avoid water loss and may have improved CO2 diffusion, characteristics that are important for drought-tolerant plants.

Do photosynthetic metabolism and habitat influence foliar water uptake in orchids?

Epiphytic and rupicolous plants inhabit environments with limited water resources. Such plants commonly use Crassulacean Acid Metabolism (CAM), a photosynthetic pathway that accumulates organic acids in cell vacuoles at night, so reducing their leaf water potential and favouring water absorption. Foliar water uptake (FWU) aids plant survival during drought events in environments with high water deficits. We hypothesized that FWU represents a strategy employed by epiphytic and rupicolous orchids for water acquisition and that CAM will favour increased water absorption. We examined 6 epiphyte, 4 terrestrial and 6 rupicolous orchids that use C3 (n = 9) or CAM (n = 7) pathways. Five individuals per species were used to evaluate FWU, structural characteristics and leaf water balance. Rupicolous species with C3 metabolism had higher FWU than other species. FWU (Cmax and k) could be related to succulence, SLM and leaf RWC. The results indicated that high orchid leaf densities favoured FWU, as area available for water storage increases with leaf density. Structural characteristics linked to water storage (e.g. high RWC, succulence), on the other hand, could limit leaf water absorption by favouring high internal leaf water potentials. Epiphytic, rupicolous and terrestrial orchids showed FWU. Rupicolous species had high levels of FWU, probably through absorption from mist. However, succulence in plants with CAM appears to mitigate FWU.

Vascular traits of stem galls: Cell increment versus morphogenetic constraints in wood anatomy.

Eremanthus erythropappus hosts globoid stem galls induced by Neolasioptera sp. (Diptera: Cecidomyiidae) close to the stem apex, which do not compromise the shoot apical meristem (SAM). We hypothesize that maintenance of the SAM, as well as the increasing number of leaves per branch and of galled stem lengths and diameters, are a consequence of alterations in vascular cells and, consequently, in the priority for water flow from non-galled stems to the stem galls. Our study focuses on the globoid stem galls to evaluate if gall induction and development promote changes in structure and function of secondary xylem cells. Anatomical, cytological, histometric and physiological methods were used to analyse non-galled stem branches (NGS), mature globoid stem galls and stem portions below and above the galls. These analyses revealed that vessel elements are larger in stem galls and in stem portions above the galls. Under Neolasioptera sp. induction activity, the vascular cambium of E. erythropappus produces less numerous but larger vessel elements and overproduces parenchyma cells. Contrary to the vascular constriction hypothesis proposed for bacterial galls, the vascular traits of the Neolasioptera sp. stem galls on E. erythropappus result in priority for water flow to galls and the non-galled portions above the galls, allowing the maintenance of galled stem growth and development.

Xylem embolism spread is largely prevented by interconduit pit membranes until the majority of conduits are gas-filled.

Xylem embolism resistance varies across species influencing drought tolerance, yet little is known about the determinants of the embolism resistance of an individual conduit. Here we conducted an experiment using the optical vulnerability method to test whether individual conduits have a specific water potential threshold for embolism formation and whether pre-existing embolism in neighbouring conduits alters this threshold. Observations were made on a diverse sample of angiosperm and conifer species through a cycle of dehydration, rehydration and subsequent dehydration to death. Upon rehydration after the formation of embolism, no refilling was observed. When little pre-existing embolism was present, xylem conduits had a conserved, individual embolism-resistance threshold that varied across the population of conduits. The consequence of a variable conduit-specific embolism threshold is that a small degree of pre-existing embolism in the xylem results in apparently more resistant xylem in subsequent dehydrations, particularly in angiosperms with vessels. While our results suggest that pit membranes separating xylem conduits are critical for maintaining a conserved individual conduit threshold for embolism when little pre-existing embolism is present, as the percentage of embolized conduits increases, gas movement, local pressure differences and connectivity between conduits increasingly contribute to embolism spread.

Hydrogen peroxide is involved in drought stress long-distance signaling controlling early stomatal closure in tomato plants / O peróxido de hidrogênio está envolvido na sinalização de longa distância do déficit hídrico controlando o fechamento estomático precoce em plantas de tomate

It has long been hypothesized that hydrogen peroxide (H2O2) may play an essential role in root-to-shoot long-distance signaling during drought conditions. Thus, to better understand the involvement of H2O2 in drought signaling, two experiments were carried out using tomato plants. In the first experiment, a split-root scheme was used, while in the second experiment, the tomato plants were grown in a single pot and subjected to drought stress. In both experiments, H2O2 and catalase were applied together with irrigation. Control plants continued to be irrigated according to the water loss. In the split-root experiment, it was verified that the application of H2O2 to roots induced a clear reduction in plant transpiration compared to untreated or catalase-treated plants. In the second experiment, we observed that H2O2-treated plants exhibited similar transpiration when compared to untreated and catalase-treated plants under drought stress. Similarly, no difference in water use efficiency was observed. Thus, we conclude that the increase in H2O2 in the root system can act as a long-distance signal leading to reduced transpiration even when there is no water limitation in the shoot. But it has little effect when there is a reduction in the shoot water potential.

Tem sido hipotetizado que o peróxido de hidrogênio (H2O2) pode desempenhar um papel essencial na sinalização de longa distância entre a raiz e a parte aérea sob condições de seca. Assim, para melhor entender o envolvimento do H2O2 na sinalização da seca, dois experimentos foram realizados com plantas de tomate. No primeiro, foi utilizado o esquema de raízes divididas, enquanto no segundo, os tomateiros foram cultivados em um único vaso e submetidos ao déficit hídrico. Em ambos os experimentos, o H2O2 e a catalase foram aplicados juntamente com a irrigação. As plantas do grupo controle continuaram a ser irrigadas de acordo com a perda de água. No experimento de raiz dividida, verificou-se que a aplicação de H2O2 nas raízes induziu uma clara redução na transpiração da planta em comparação com plantas não tratadas ou tratadas com catalase. No segundo experimento, observamos que plantas tratadas com H2O2 apresentaram transpiração semelhante quando comparadas com plantas não tratadas e tratadas com catalase sob seca. Da mesma forma, não foi observada diferença na eficiência do uso da água. Assim, concluímos que o aumento do H2O2 no sistema radicular pode atuar como um sinal de longa distância levando à redução da transpiração mesmo quando não há limitação hídrica na parte aérea. Mas tem pouco efeito quando há redução do potencial hídrico da parte aérea.

Ecophysiological responses and self-protective canopy effects of surfgrass (Phyllospadix torreyi) in the intertidal.

Intertidal seagrasses are subjected to desiccation and direct solar radiation during low tides. It is assumed that the canopy structure can self-protect the underlying shoots during these events, although there is no evidence on a physiological basis. The physiological responses of the surfgrass Phyllospadix torreyi were examined when emerged during low tide, on i) shoots overlaying the canopy, and ii) shoots sheltered within the canopy. Leaf water potential and water content decreased in external leaves after emersion, and the higher concentration of organic osmolytes reflected osmoregulation. Additionally, these shoots also exhibited a drastic reduction in carbohydrates after re-immersion, likely from cellular damage. Lipid peroxidation and antioxidant activity increments were also detected, while photosynthetic efficiency strongly diminished from direct exposure to solar radiation. Conversely, the sheltered shoots did not dehydrate and solely accumulated some oxidative stress, likely resulting from the warming of the canopy. In conclusion, the leaf canopy structure buffers physiological stress in the sheltered shoots, thus acting as a self-protective mechanism to cope with emersion.

Photosynthetic heat tolerance in plants with different foliar water -uptake strategies.

PREMISE: The distribution and even the survival of plant species are influenced by temperature. In an old climatically buffered infertile landscape (OCBIL) in Brazil, we previously characterized different strategies for foliar water uptake (FWU). It is possible that photosystem II tolerance to heat and excessive light intensity varies among species with different FWU capacities. METHODS: The relationship between FWU, photoinhibition, and thermotolerance was investigated in seven species from this ecosystem. RESULTS: The species with slow water absorption and high water absorption are those that presented less photoinhibition. Contrastingly, the species that have fast and low water absorption presented greater thermotolerance when their leaves are totally hydrated. However, when there is greater leaf dehydration, the most thermotolerant species were those with slow but high water absorption. CONCLUSIONS: Foliar water uptake is an important trait for plants to tolerate excessive light intensity and higher temperatures. Plants in this OCBIL may be differentially affected by future global warming, and the best strategy to deal with this expected climate change is with slow and high absorption of water.

Root hydraulics adjustment is governed by a dominant cell-to-cell pathway in Beta vulgaris seedlings exposed to salt stress.

Soil salinity reduces root hydraulic conductivity (Lpr) of several plant species. However, how cellular signaling and root hydraulic properties are linked in plants that can cope with water restriction remains unclear. In this work, we exposed the halotolerant species red beet (Beta vulgaris) to increasing concentrations of NaCl to determine the components that might be critical to sustaining the capacity to adjust root hydraulics. Our strategy was to use both hydraulic and cellular approaches in hydroponically grown seedlings during the first osmotic phase of salt stress. Interestingly, Lpr presented a bimodal profile response apart from the magnitude of the imposed salt stress. As well as Lpr, the PIP2-aquaporin profile follows an unphosphorylated/phosphorylated pattern when increasing NaCl concentration while PIP1 aquaporins remain constant. Lpr also shows high sensitivity to cycloheximide. In low NaCl concentrations, Lpr was high and 70 % of its capacity could be attributed to the CHX-inhibited cell-to-cell pathway. More interestingly, roots can maintain a constant spontaneous exudated flow that is independent of the applied NaCl concentration. In conclusion, Beta vulgaris root hydraulic adjustment completely lies in a dominant cell-to-cell pathway that contributes to satisfying plant water demands.

Hourly Relationship between Reference Evapotranspiration and Shoot Shrinkage in Walnut Trees and Pomegranate under Deficit Irrigation.

Diameter fluctuations of branches, shoots, or fruits are related to plant transpiration and water potential. In the past, several models have related dendrometric variables and evapotranspiration on a daily scale. However, trunk-branch shrinkage occurs only between dawn and midday, while evapotranspiration occurs most of the day from sunrise to sunset. Previous models have failed to incorporate this key fact. The objective of the present study was to assess the relationship of hourly daily shrinkage (HDS) between dawn and the next 4 h to the hourly reference evapotranspiration (EToh) of the same period in walnut trees and pomegranate plants under different irrigation regimes. Our data show that the relationship between EToh and HDS is much better than several previous models that included maximum daily shrinkage (MDS) and reference evapotranspiration (ETo). The novel slope analysis of the relationship between HDS versus time used here corresponds to the velocity at which the HDS occurs, which depends on the ETo intensity at that moment. This new method of analyzing this type of data calls for a revision of these models and sets a new baseline for future analysis.

Performance Assessment of Thermal Infrared Cameras of Different Resolutions to Estimate Tree Water Status from Two Cherry Cultivars: An Alternative to Midday Stem Water Potential and Stomatal Conductance.

The midday stem water potential (Ψs) and stomatal conductance (gs) have been traditionally used to monitor the water status of cherry trees (Prunus avium L.). Due to the complexity of direct measurement, the use of infrared thermography has been proposed as an alternative. This study compares Ψs and gs against crop water stress indexes (CWSI) calculated from thermal infrared (TIR) data from high-resolution (HR) and low-resolution (LR) cameras for two cherry tree cultivars: 'Regina' and 'Sweetheart'. For this purpose, a water stress-recovery cycle experiment was carried out at the post-harvest period in a commercial drip-irrigated cherry tree orchard under three irrigation treatments based on Ψs levels. The water status of trees was measured weekly using Ψs, gs, and compared to CWSIs, computed from both thermal cameras. Results showed that the accuracy in the estimation of CWSIs was not statistically significant when comparing both cameras for the representation of Ψs and gs in both cultivars. The performance of all evaluated physiological indicators presented similar trends for both cultivars, and the averaged differences between CWSI's from both cameras were 11 ± 0.27%. However, these CWSI's were not able to detect differences among irrigation treatments as compared to Ψs and gs.

Extremely low frequency non-uniform magnetic fields induce changes in water relations, photosynthesis and tomato plant growth.

Purpose: To elucidate the effects during the vegetative growth of pre-sowing magnetic treatments on water relations, photosynthesis and plant growth in tomato (Vyta) plants under greenhouse conditions.Materials and methods: Tomato seeds were exposed to full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 120 mT (rms) for 10 min and at 80 mT (rms) for 5 min. Non-treated seeds were used as controls. Plants were grown in polystyrene trays and water relations, photosynthesis and plant growth were measured.Results: Plants from magnetically treated seeds maintained better leaf water status in terms of increases in leaf water potential, leaf osmotic potential, leaf turgor potential and relative water content, and decreases in stomatal conductance and transpiration rate. Net photosynthesis rate, chlorophyll a, chlorophyll b, carotenoids and total chlorophyll contents increase in plants from magnetically exposed seeds compared to controls. The MF treatments lead to a notable increase in root length, plant height, root and shoot dry mass, leaf area per plant, and root and shoot relative growth rates.Conclusions: Application of full-wave rectified sinusoidal non-uniform MF as a pre-sowing treatment has the potential to improve tomato plant vegetative growth through the enhancement of water relations and photosynthesis.

Eco-Physiological Traits Related to Recovery from Complete Submergence in the Model Legume Lotus japonicus.

Submergence is a severe form of stress for most plants. Lotus japonicus is a model legume with potential use in assisting breeding programs of closely related forage Lotus species. Twelve L. japonicus genotypes (10 recombinant inbred lines (RILs) and 2 parental accessions) with different constitutive shoot to root dry mass ratios (S:R) were subjected to 7 days of submergence in clear water and allowed to recover for two weeks post-submergence; a set of non-submerged plants served as controls. Relative growth rate (RGR) was used to indicate the recovery ability of the plants. Leaf relative water content (RWC), stomatal conductance (gs), greenness of basal and apical leaves, and chlorophyll fluorescence (Fv/Fm, as a measure of photoinhibition) were monitored during recovery, and relationships among these variables and RGR were explored across genotypes. The main results showed (i) variation in recovery ability (RGR) from short-term complete submergence among genotypes, (ii) a trade-off between growth during vs. after the stress indicated by a negative correlation between RGR during submergence and RGR post-submergence, (iii) an inverse relationship between RGR during recovery and S:R upon de-submergence, (iv) positive relationships between RGR at early recovery and RWC and gs, which were negatively related to S:R, suggesting this parameter as a good estimator of plant water balance post-submergence, (v) chlorophyll retention allowed fast recovery as revealed by the positive relationship between greenness of basal and apical leaves and RGR during the first recovery week, and (vi) full repair of the submergence-damaged photosynthetic apparatus occurred more slowly (second recovery week) than full recovery of plant water relations. The inclusion of these traits contributing to submergence recovery in L. japonicus should be considered to speed up the breeding process of the closely related forage Lotus spp. used in current agriculture.

Growing broccoli under salinity: the influence of cultivar and season on glucosinolates content

The evaluation of factors that affect glucosinolates (GLS) concentrations in the roots, leaves, and inflorescence of broccoli plants is important in the improvement of the concentration of bioactive compounds and thus in the enhancement of the nutritional properties. In this work, the yield and the concentration of GLS of seven broccoli cultivars (Brassica oleracea var. italica) grown under salinity in field conditions were studied during three different seasons (autumn, winter, and spring). The results show that, generally, salinity did not alter significantly the inflorescence yield during any of the seasons, indicating a high tolerance of the cultivars tested. Yield was reduced only in cultivar Gea in autumn and in cultivar Parthenon in spring. The distribution of the GLS showed that their accumulation was greater in inflorescences and leaves, with higher concentrations in autumn and spring. The activation of GLS synthesis by salinity was restricted to several cultivars and depended on the season, with no reductions compared to control plants. In this study, we discuss the appearance of a Cinnamoyl-indol-GLS derivative in some of the cultivars and seasons with higher incidence in NaCl-treated plants.

Growing broccoli under salinity: the influence of cultivar and season on glucosinolates content

The evaluation of factors that affect glucosinolates (GLS) concentrations in the roots, leaves, and inflorescence of broccoli plants is important in the improvement of the concentration of bioactive compounds and thus in the enhancement of the nutritional properties. In this work, the yield and the concentration of GLS of seven broccoli cultivars (Brassica oleracea var. italica) grown under salinity in field conditions were studied during three different seasons (autumn, winter, and spring). The results show that, generally, salinity did not alter significantly the inflorescence yield during any of the seasons, indicating a high tolerance of the cultivars tested. Yield was reduced only in cultivar Gea in autumn and in cultivar Parthenon in spring. The distribution of the GLS showed that their accumulation was greater in inflorescences and leaves, with higher concentrations in autumn and spring. The activation of GLS synthesis by salinity was restricted to several cultivars and depended on the season, with no reductions compared to control plants. In this study, we discuss the appearance of a Cinnamoyl-indol-GLS derivative in some of the cultivars and seasons with higher incidence in NaCl-treated plants.(AU)

Controversies in Midday Water Potential Regulation and Stomatal Behavior Might Result From the Environment, Genotype, and/or Rootstock: Evidence From Carménère and Syrah Grapevine Varieties.

Controversies exist regarding the iso/anisohydric continuum for classifying plant water-use strategies. Isohydricity has been argued to result from plant-environment interaction rather than it being an intrinsic property of the plant itself. Discrepancies remain regarding the degree of isohydricity (σ) of plants and their threshold for physiological responses and resistance to drought. Thus, the aim of this study was to evaluate the isohydricity of the grapevine varieties Syrah and Carménère under a non-lethal water deficit progression from veraison from two different locations, the Cachapoal Valley (CV) and Maipo Valley (MV), in central Chile and with different rootstock only in Syrah. For this purpose, the midday stem water potential (Ψmds) regulation and stomatal responses to drought, leaf traits related to pressure-volume curves, stomatal sensitivity to ABA, cavitation threshold, and photosynthetic responses were assessed. A higher atmospheric water demand was observed in the CV compared to the MV, with lower Ψmds values in the former for both varieties. Also, the σ values in Carménère were 1.11 ± 0.14 MPa MPa-1 and 0.68 ± 0.18 MPa MPa-1 in the CV and MV, respectively, and in Syrah they were 1.10 ± 0.07 MPa MPa-1 in the CV and 0.60 ± 0.10 MPa MPa-1 in the MV. Even though similar variations in σ between locations in both varieties were evident, Carménère plants showed a conserved stomatal response to Ψmds in both study sites, while those of Syrah resulted in a higher stomatal sensitivity to Ψmds in the site of lower σ. Besides the differences in seasonal weather conditions, it is likely that the different rootstock and clonal variability of each season in Syrah were able to induce coordinated changes in σ, Ψgs12, and osmotic potential at full turgor (π0). On the other hand, irrespective of the σ, and given the similarity between the π0 and Ψgs12 in leaves before drought, it seems that π0 could be a convenient tool for assessing the Ψmds threshold values posing a risk to the plants in order to aid the irrigation decision making in grapevines under controlled water deficit. Finally, water deficits in vineyards might irreversibly compromise the photosynthetic capacity of leaves.