Severe Water Deficit Research Articles

Rubber Genotypes with Contrasting Drought Factor Index Revealed Different Mechanisms for Drought Resistance in Hevea brasiliensis.

It is predicted that drought will be more frequent and sustained in the future, which may affect the decline of rubber tree production. Therefore, it is critical to research some of the variables related to the drought-resistance mechanism of the rubber tree. As a result, it can be used to guide the selection of new rubber drought-resistance clones. The goal of this study was to identify drought-resistance mechanisms in rubber clones from the high drought factor index (DFI) group using ecophysiological and biochemical variables. The treatments consist of two factors, namely water deficit and contrasting clones based on the DFI variable. The first factor consisted of three levels, namely normal (fraction of transpirable soil water (FTSW) > 0.75), severe water deficit (0.1 < FTSW < 0.20), and recovery condition (FTSW > 0.75 after rewatering). The second factor consisted of seven clones, namely clones G239, GT1 (low DFI), G127, SP 217, PB 260 (moderate DFI), as well as G206 and RRIM 600 (high DFI). RRIM 600 had the highest DFI among the other clones as a drought-tolerance mechanism characteristic. Furthermore, clones RRIM 600, GT1, and G127 had lower stomatal conductance and transpiration rate than drought-sensitive clone PB 260. As a result, as drought avoidance mechanisms, clones RRIM 600, GT1, and G127 consume less water than clone PB 260. These findings indicated that clone RRIM 600 was a drought-resistant clone with drought tolerance and avoidance mechanisms.

Concurrent time course of xylem hydraulic dysfunction and non-structural carbohydrates under contrasting water deficits and nitrogen supplies in poplar

We compared the temporal dynamics of growth, leaf gas exchange, xylem hydraulic dysfunction and non-structural carbohydrates (NSC) of two poplar hybrid genotypes subjected to a differential nitrogen (N) supply under contrasting water deficits. Moderate water deficit generated intermediate embolism rates (45–70%) but had marginal effects on NSC. Severe water deficit generated progressive hydraulic failure and NSC reduction, leading to tree death within 90 days. At death, NSC in perennial tissues were not entirely depleted because of remaining soluble sugars. Higher N availability primarily affected growth and NSC dynamics (mainly starch), not embolism dynamics. The faster growing genotype benefiting most from N addition ceased growth and photosynthesis almost simultaneously, with no effect of N addition on process cessation, leading to progressive starch depletion during severe drought. In contrast, the slower growing genotype ceased growth before photosynthesis, leading to a transient increase in starch concentration during early drought stages, but this tended to be suppressed by higher N availability. Altogether, our findings indicate that carbon starvation alone is unlikely in hydraulically vulnerable species such as poplar even under prolonged moderate water deficit, but starch relative depletion covaries in time with progressive hydraulic failure under lethal water deficit. Nutritional status has the potential to shape drought responses, primarily through adjustments in carbon source-sink relations rather than in intrinsic xylem hydraulics, in a genotype-dependent manner. Exploring how hydraulic and carbon safety margins can be coordinated within species would be valuable in understanding how variation in drought response strategies can be exploited in breeding/selection.

Adaptabilities of Water Production Function Models for Rice in Cold and Black Soil Region of China

Crop water production function models (WPFMs) are required methods to study the relationships between yield and water consumption under regulated deficit irrigation (RDI). In this study, a pot experiment was established to study the effect of water deficit during both individual growth stages and across two consecutive growth stages of rice on yield, water consumption, and water use efficiency (WUE) in 2017 and 2018. Light, medium, and severe water deficits were set as 80~90%, 70~80%, and 60~70% of saturated soil moisture content, respectively. The accuracies of five WPFMs were tested based on the experimental results. The results showed that yields and WUE of a light water deficit were higher than those of medium and severe water deficits at each growth stage. The yields and WUE of light drought stress treatments in the flowering and milky stages were higher than the saturated soil moisture control by 4~7.4% and 5.3~20.6%, respectively. Water consumption decreased with increasing water deficit across two consecutive growth stages. The Minhas model had the highest simulation accuracy of the five WPFMs, with relatively lower AE, RMSE, Cv, CRM, and higher R2, which were 0.0002, 0.0634, 6.9965, 0.0002, and 0.9951 in 2017 and 0.0110, 0.0760, 8.9882, 0.0131, and 0.9923 in 2018, respectively. The sensitivity indices for the Minhas model more accurately reflected the sensitivity of rice yield to water deficit at different growth stages in 2017 and 2018, compared with the Jensen model, Stewart model, Blank model, and Singh model. Rice yield was most sensitive to water deficit at the jointing and booting stage. The results indicate that the Minhas model is the most suitable WPFM for guiding rice irrigation practices in cold and black soil regions of China.

Deficit irrigation scheduling with mulching and yield prediction of guava (Psidium guajava L.) in a subtropical humid region

Drip irrigation and mulching are often used to alleviate the problem of poor water management in many crops; however, these technologies have not yet been tested for applying water at critical stages of guava orchard growth in subtropical humid Tarai regions of India to improve the yield and quality. A field experiment was conducted over 2020 and 2021 which included three irrigation strategies: severe deficit irrigation (DI50), moderate deficit irrigation (DI75), and full irrigation (FI100), as well as four mulching methods: silver-black mulch (MSB), black mulch (MB), organic mulch (MOM), and a control without mulch (MWM). The results showed that both the relative leaf water content (RLWC) and the proline content exhibited an increasing trend with a decrease in the irrigation regime, resulting in a 123% increase in the proline content under DI50 conditions compared with FI100, while greater plant growth was recorded in fully irrigated plants and using silver-black mulch. Leaf nutrient analysis showed that FI100 and MOM produced significantly higher concentrations of all nutrients. However, moderate deficit irrigation (DI75) along with silver-black mulch (MSB) produced higher numbers of fruits per plant, higher average fruit weights, higher fruit yields, and maximum ascorbic acid contents. The irrigation water productivity (IWP) decreased with an increase in the irrigation regime; from severe water deficit to full irrigation, resulting in a 33.79% improvement in IWP under DI50 conditions as compared with FI100. Regression analysis outperforms principal component regression analysis for fruit yield prediction, with adjusted R2 = 89.80%, RMSE = 1.91, MAE = 1.52, and MAPE = 3.83. The most important traits affecting the fruit yield of guava, based on stepwise regression, were leaf proline, leaf Cu, fruit weight, and IWP.

Relative Water Content, Proline, and Antioxidant Enzymes in Leaves of Long Shelf-Life Tomatoes under Drought Stress and Rewatering.

Some physiological, oxidative, and antioxidant enzymatic patterns were assessed in plants of three local Sicilian landraces of long shelf-life tomatoes ('Custonaci', 'Salina', and 'Vulcano'), as compared to the commercial tomato hybrid 'Faino' (control). Three water treatments were considered in open-field: DRY (no irrigation); IRR (long-season full irrigation); REW (drought/rewatering cycles). During the growing season, soil water deficit (SWD) was estimated, and relative water content (RWC), specific leaf area (SLA), proline and malondialdehyde (MDA) content, and glutathione peroxidase (GPX), catalase (CAT), and superoxide dismutase (SOD) activities were measured in leaves. Differently from control, RWC in local landraces exhibited a similar pattern in REW and DRY, indicating a low capacity to re-hydrate after rewatering. Positive correlation of proline content vs. SWD in all local landraces highlights an osmotic adjustment occurring in these tomatoes in response to limited soil water content. Long shelf-life tomatoes suffered minor oxidative stress due to severe soil water deficit, as revealed by the lower levels of MDA with respect to the control. Significant correlation of CAT vs. SWD for all tomatoes indicates that this antioxidant enzyme, among those analyzed, may be considered as a biomarker for a water stress condition more than for oxidative stress due to water deficit.

Abscisic acid metabolism pathways differ between grapevine species, leaves, and roots during water deficit

Abscisic acid (ABA) metabolism is complex involving biosynthesis, conjugation, and catabolism. Differences in ABA metabolism (ABA, ABA-related metabolites, and transcripts) in response to water deficit (WD) were detected in leaves and roots of four Vitis species differing in drought tolerance: Vitis vinifera (Cabernet Sauvignon), Vitis champinii (Ramsey), Vitis riparia (Riparia Gloire), and Vitis vinifera x girdiana (SC2). Concentrations of ABA and ABA-related metabolites increased after moderate or severe WD depending on species, organ, and time. Differences in ABA, glycosylated-ABA, and ABA catabolite concentrations, as well as previously investigated related transcript abundances, revealed differences in ABA metabolism pathways among the species and organs. NCED3 was a key gene in the WD response of leaves and roots of all species. NCED3 transcript abundance and ABA concentration in drought-tolerant Ramsey increased earlier and to a greater extent than other species. These species provide informative genetic resources to study ABA metabolism and drought tolerance further.

Dissection of Genetic Effects, Heterosis, and Inbreeding Depression for Phytochemical Traits in Coriander.

Increasing seed yield, fatty acids, and essential oil content are the main objectives in breeding coriander. However, in order to achieve this, there is a need to understand the nature of gene action and quantify the heterosis and inbreeding depression. Towards this, six genetically diverse parents, their 15 F1 one-way hybrids, and 15 F2 populations were evaluated under different water treatments. The genetic effects of general (GCA) and specific combining ability (SCA) and their interactions with water treatment were significant for five traits. Water deficit stress decreased all traits in both F1 and F2 generations except for the essential oil content, which was significantly increased due to water deficit stress. Under water deficit stress, a non-additive gene action was predominant in the F1 generation, while an additive gene action was predominant in the F2 generation for all the traits except seed yield under severe water deficit stress. There was a positive high heterosis for the traits examined in some hybrids. Furthermore, in the F2 generation, even after inbreeding depression, some promising populations displayed appropriate mean performance. The results show that the parents used for crossing had a rich, diverse gene pool for the traits studied. Therefore, selection between the individuals of relevant F2 populations could be used to develop high yielding hybrids or superior lines.

Berry flavonoids are differently modulated by timing and intensities of water deficit in Vitis vinifera L. cv. Sangiovese.

In this work, we tested the effect of different regulated deficit irrigation (RDI) regimes on berry flavonoid content and its relative biosynthetic pathways. Vines were subjected to six irrigation regimes over two consecutive years: a) full irrigation during the entire irrigation period (FI); b) moderate (RDI-1M) or c) severe (RDI-1S) water deficit between berry pea-size and veraison; d) severe water deficit during the lag-phase (RDI-LS); and e) moderate (RDI-2M) or f) severe (RDI-2S) water deficit from veraison through harvest. Berries from both RDI-1 treatments showed the highest accumulation of anthocyanins, upregulating the expression of many genes of the flavonoid pathway since the beginning of veraison until harvest, far after the water deficit was released. Although to a lesser degree than RDI-1, both post-veraison water deficit treatments increased anthocyanin concentration, particularly those of the tri-substituted forms, overexpressing the F3'5'H hydroxylases. The moderate deficit irrigation treatments enhanced anthocyanin accumulation with respect to the severe ones regardless of the period when they were applied (pre- or post-veraison). The water deficit imposed during the lag-phase downregulated many genes throughout the flavonoid pathway, showing a slight reduction in anthocyanin accumulation. The measurements of cluster temperature and light exposure highlighted that under deficit irrigation conditions, the effects induced by water stress prevailed over that of light and temperature in regulating anthocyanin biosynthesis. Flavonol concentration was higher in RDI-1S berries due to the upregulation of the flavonol synthases and the flavonol-3-O-glycosyltransferases. In this case, the higher cluster light exposure induced by water deficit in RDI-1S berries had a major role in flavonol accumulation. We conclude that the timing and intensity of water stress strongly regulate the berry flavonoid accumulation and that proper management of deficit irrigation can modulate the phenylpropanoid and flavonoid pathways.

Short-term severe drought influences root volatile biosynthesis in eastern white pine (Pinus strobus L).

Climate change-related drought stress is expected to shift carbon partitioning toward volatile organic compound (VOC) biosynthesis. The effect of drought stress on VOC synthesis remains unknown in several tree species. Therefore, we exposed eastern white pine (Pinus strobus) plants to severe drought for 32 days and performed physiological analysis (chlorophyll content, leaf water content, and root/shoot index), biochemical analysis (non-structural carbohydrates, proline, lipid peroxidation, and antioxidant assay), and total root VOC analysis. Drought stress decreased the relative water and soil moisture contents. Root proline accumulation and antioxidant activity increased significantly, whereas leaf chlorophyll synthesis and fresh weight decreased significantly in drought-treated plants. A non-significant increase in sugar accumulation (leaves and roots), proline accumulation (leaves), antioxidant activity (leaves), and lipid peroxidation (leaves and roots) was observed in drought-treated plants. Drought stress caused a non-significant decline in root/shoot ratio and starch accumulation (leaves and roots) and caused a significant increase in root abscisic acid content. Drought-treated plants showed an increase in overall monoterpene synthesis (16%) and decline in total sesquiterpene synthesis (3%). Our findings provide an overall assessment of the different responses of VOC synthesis to severe water deficit that may help unravel the molecular mechanisms underlying drought tolerance in P. strobus.

Action of silicon on the activity of antioxidant enzymes and on physiological mechanisms mitigates water deficit in sugarcane and energy cane plants

Production of sugarcane and more recently of energy cane strengthen renewable bioenergy production capacity. However, droughts resulting from climate change have limited the production of these crops. One of the strategies to attenuate water deficit damage in these crops is the use of silicate, which contributes to plant physiology. This strategy is likely to increase water use efficiency, thus promoting crop sustainability. Notwithstanding, studies on this issue are still incipient. This study assesses whether Si applied via fertigation and foliar spraying in the seedling production phase and as a complement after seedling transplanting to the soil is efficient in attenuating water deficit in sugarcane and energy cane. The study further elucidates physiological and biochemical mechanisms involved in this process. For this, the authors conducted two experiments: one with sugarcane and the other with energy cane. Treatments were arranged in randomized blocks with 5 replications, in a 2 × 2 factorial scheme. Factors consisted of the absence (-Si) and presence of Si (+ Si) applied via fertigation and foliar spraying; and two water regimes: 70% (without water deficit) and 30% (severe water deficit) of the soil water retention capacity. Silicon was supplied during the formation phase of presprouted seedlings and during the transplanting of seedlings to pots filled with samples of Entisol (Quartzipsamment). In these pots, water regimes were induced from 7 to 160 days after transplanting. Severe water deficit reduced the water content and water potential of plants. This situation induced oxidative stress and impaired gas exchange and photosynthetic water use efficiency, reducing plant growth. Silicon supply via fertigation in association with foliar spraying in the seedling formation phase with complementation after transplanting was efficient in increasing Si accumulation in the plants. Silicon was effective in attenuating severe water deficit damage up to initial culm formation through mechanisms that maintain water and physiological balance by favoring the antioxidant defense system in sugarcane and energy cane plants.

Arbuscular Mycorrhizal Fungi Promote Physiological and Biochemical Advantages in Handroanthus serratifolius Seedlings Submitted to Different Water Deficits.

Climate change causes increasingly longer periods of drought, often causing the death of plants, especially when they are in the early stages of development. Studying the benefits provided by arbuscular mycorrhizal (AM) fungi to plants in different water regimes is an efficient and sustainable strategy to face climate change. Thus, this study investigated the influence of AM fungi on Handroanthus serratifolius seedlings under different water regimes, based on biochemical, and nutritional growth parameters. The experiment was carried out in H. serratifolius seedlings cultivated with mycorrhizas (+AMF) and without mycorrhizas (-AMF) in three water regimes; a severe water deficit (SD), a moderate water deficit (MD), and a well-watered (WW) condition. AM fungi provided greater osmoregulation under water deficit conditions through the accumulation of soluble sugars, total free amino acids, and proline, as well as by reducing sugar. The increase in the absorption of phosphorus and nitrate was observed only in the presence of fungi in the well-watered regimen. A higher percentage of colonization was found in plants submitted to the well-watered regimen. Ultimately, AM fungi promoted biochemical, nutritional, and growth benefits for H. serratifolius seedlings under the water deficit and well-hydrated conditions, proving that AMF can be used to increase the tolerance of H. serratifolius plants, and help them to survive climate change.

Effects of Different Irrigation and Drainage Modes on Lodging Resistance of Super Rice Japonica 9108

In order to determine the optimal irrigation and drainage mode for the anti-lodging cultivation of Super Rice Japonica 9108, barrel loading tests of different irrigation and drainage modes were carried out in the Water-Saving Park of Hohai University in Nanjing from June to October in 2019 and 2020. Three treatments were set up: Frequent and Shallow Irrigation (FSI), Rain-catching and Controlled Irrigation (RC-CI) and Drought Planting with Straw mulching (DPS). In each mode, the growth index, stem morphology index, material production index and stem mechanical index of rice at yellow maturity period were measured, and their relationship with the lodging index was analyzed. The results showed that compared with FSI, the lodging index of RC-CI was reduced by an average of 24.0%. RC-CI can promote the lateral development of the base internodes, increase the accumulation of stem sheath dry matter and the internode fullness and enhance mechanical strength and anti-lodging ability of the stem. Meanwhile, RC-CI can appropriately reduce the plant height, so as to reduce the bending moment of the base internodes. As a consequence, the lodging risk was effectively reduced. The lodging index of DPS was reduced by an average of 16.0% compared with FSI. Because DPS was subject to severe water deficit, its internodes thickness and stem wall thickness were inferior to that of FSI, leading to the weakening of the mechanical strength of stem, and the morphological characteristics and mechanical characteristics of the stem were not improved. Despite this, DPS still had a strong resistance to lodging. The output rate and conversion rate of the stem sheath were reduced, and while the plant height and center of gravity height were significantly reduced, the bending moment remained low. Thus, DPS can still reduce the lodging risk of rice. Compared with FSI, the average yield of RC-CI increased by 5.8% in two years, and the average yield of DPS was reduced by 4.4% in two years. DPS under severe water deficit reduced the accumulation of dry matter in the panicle and the yield index of rice, which was not conducive to a high yield. Considering the yield and lodging resistance of the super rice “Japonica 9108”, RC-CI is the best irrigation and drainage mode, followed by DPS. This study can provide data support and theoretical support for regulating the lodging resistance of super rice through irrigation measures.

Deficit mulched drip irrigation improved yield and quality while reduced water consumption of isatis indigotica in a cold and arid environment.

Deficit irrigation is an effective alternative to traditional irrigation, as it improves crop productivity and conserves water. However, crops may be sensitive to deficit irrigation-induced water stress at different periods. To access the effect of deficit irrigation on the growth, water consumption characteristics, yield, and quality of Isatis indigotica (woad), we performed a three-year (2017-2019) mulched drip irrigation field experiment. Woad plants were provided adequate water supply at the seedling stage but were subjected to mild (65–75% field water capacity FC), moderate (55–65% FC), and severe (45–55% FC) water deficit at the vegetative growth, fleshy root growth and fleshy root maturity stages, respectively; plants supplied with adequate water throughout the growth period served as a control (CK, 75–85% FC). The water consumption characteristics, agronomic traits, dry matter content and distribution, yield, and quality of these plants were measured at various growth stages. The results showed that the total water consumption in water deficit was significantly less than that in CK by 4.44–10.21% (P< 0.05). The dry matter content of plants treated with moderate (WT2 and WT5) and severe (WT3) water deficit was reduced by 12.83–28.75%. The economic yield of mild water deficit-treated plants was higher during vegetative growth (WT1) and fleshy root growth (WT4), while the water use efficiency of these plants was significantly increased by 7.84% and 6.92% at the two growth stages, respectively. Continuous mild water deficit (WT4) enhanced the contents of indigo, indirubin, (R,S)-goitrin, polysaccharides, and soluble proteins during vegetative growth and fleshy root growth, while moderate and severe water deficit were detrimental to the quality of woad plants. Thus, continuous mild water deficit during vegetative and fleshy root growth periods (WT4) is optimal for the cultivation of woad in the cold and cool irrigation district of the Hexi Oasis region.

Causes and course of climate change and its hydrological consequences in the Greater Poland region in 1951-2020

The paper presents effects of changes in climatic elements in the Greater Poland region (Poland), their causes and consequences for shaping the water balance of this area, copying with the most severe water deficit in Poland. The study period covers 70 years (1951–2020). The research identified an abrupt and significant change in the climate of Greater Poland, which started between 1987 and 1989, concerning not only air temperature but also a wider spectrum of climatic elements. The change in the state of the climate, which covers the entire Atlantic-Eurasian circulation sector, re-sults from a sudden change in the macro-circulation conditions in the middle troposphere (500 hPa). The reason for the change in the mid-tropospheric circulation is an equally abrupt and simultaneous change in the intensity of the ocean heat transport by the North Atlantic thermohaline circulation (NA THC). Climate change observed in Greater Poland is manifested in an increase in sunshine duration (SD) and air temperature, a decrease in relative humidity, a change in the cloud structure, and an increase in the degree of sky coverage. The main, physical reason for an increase in air tempera-ture is a rapid and strong increase in SD in the warm half-years, which began after 1988, and a significant increase in the frequency of positive North Atlantic Oscillation (NAO) phases in winters. The ongoing climate change entails various effects, among which the most important is considered to be hydrological consequences. The water balance of Greater Poland is becoming increasingly unfavourable, mainly as a result of a rapid increase in field evaporation.

Plant growth promoting microorganisms (PGPM) as an eco-friendly option to mitigate water deficit in soybean (Glycine max L.): Growth, physio-biochemical properties and oil content

Drought, as an important challenge in Iran, affects all growth indicators for plants. Application of plant growth promoting microorganisms (PGPM) can reduce the detrimental effects of water deficit on plants. Two separate field experiments were conducted at the Tehran and Hashtrood sites, Iran in 2019 to study the influences of Azotobacter chroococcum (Az) and Piriformospora indica (Pi) or Az + Pi on growth, physio-biochemical properties and oil content of soybean (Glycine max L.) under water deficit conditions. Although water deficit dramatically reduced the plant height, percent vegetation cover and relative water content (RWC), plots treated with Az and Pi exhibited higher performance mentioned traits at both sites. Besides, co-inoculation of Az and Pi increased proline in Tehran (48.85 and 29.24% in leaf and root, respectively) and Hashtrood (46.91 and 48.91% in leaf and root, respectively) under severe water deficit. Accumulation of glycine betaine, soluble sugars and proteins increased for plots which received Az and Pi. Under severe water deficit conditions, the co-inoculation with Az and Pi enhanced the oil content of soybean by 12.87 and 9.37% at Tehran and Hashtrood sites respectively. Application of Az and Pi resulted in reducing the adverse effects of water deficit on oil quality of soybean by increasing the linoleic and linolenic acid in oil. Moreover, inoculation of soybean with Az and Pi can provide drought tolerance by improving ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD) and peroxidase (POX) activity. However, co-inoculation with Az and Pi was generally more effective in the alleviation of water deficit detrimental effects than sole inoculation with Az and Pi. Consequently, it can be a good approach for improving tolerance, growth and oil production of soybean under water deficit conditions.

Age- and Drought-Related Variation in Plant-Available Water of Rain-Fed Jujube Orchards on the Loess Plateau of China

As an important part of the large-scale ecological restoration project of “Grain for Green”, the planting area of jujube (Ziziphus jujuba) trees has increased significantly in the hilly region on the Loess Plateau of China, which aims to improve water and soil conservation and develop economic prospects of the region. Understanding the long-term effects of expanding orchards and the responses of soil water dynamics to drought are important for orchard management. Therefore, we use a space-for-time substitution to investigate the variations of plant-available water storage in returning cropland to orchards with different stand ages (2, 6, 10, and 15 years) in a normal year (NY2014, 442.1 mm rainfall) and the next year with low annual precipitation (DY2015, 388 mm rainfall). The results showed that the plant-available water storage in jujube orchards decreased with increasing stand age, and the trend was most obvious in the 60–180 cm layer. The mature stands (10 and 15 years) primarily absorbed soil water from the deep layer (180–300 cm) in DY2015, leading to negative values of plant-available water storage. The whole soil profiles were all subjected to severe water deficits in our study. The findings will help guide rain-fed orchard management in the loess hilly region of China and similar dryland regions.

Water Availability Affects the Capability of Reflectance Indices to Estimate Berry Yield and Quality Attributes in Rain-Fed Vineyards

Remote sensing methods are known to provide estimates of berry quality. However, previous studies have shown that the Normalized Difference Vegetation Index (NDVI) failed to predict berry quality attributes in rain-fed vineyards. This study explores the association of several reflectance indices with vine biophysical characteristics and berry yield and quality attributes and their temporal stability. The study was conducted in rain-fed Chardonnay vineyards located around Masquefa (Penedès region, Catalonia, Spain) over four years. Canopy reflectance, fractional Intercepted Photosynthetic Active Radiation, predawn water potential and canopy temperature at midday were measured at veraison whereas berry yield and quality attributes were determined at harvest. Water availability and vine biophysical attributes showed large temporal stability whereas berry quality attributes were not temporally stable. The capability of reflectance indices to estimate berry quality attributes was subject to the timing and extent of water deficits. The Photochemical Reflectance Index (PRI), the NDVI and the Water Index (WI) provided estimates of berry quality attributes under mild, moderate and severe water deficits, respectively. These results might have potential applications in precision viticulture activities such as selective harvesting according to grape quality attributes and the assessment of ripening.

Comparative Analysis of Tolerance to Salt Stress and Water Deficit in Two Invasive Weeds of the Genus Erigeron (Asteraceae).

Erigeron bonariensis and E. sumatrensis are two noxious weeds present in many parts of the world. Their tolerance to salinity and water deficit was analysed at the seed germination stage and during vegetative development. Seed germination was tested in solutions with different concentrations of NaCl and polyethylene glycol (PEG). Growth parameters, photosynthetic pigments, ion accumulation, and antioxidant mechanisms were analysed in plants that were subjected to increasing NaCl solutions, or severe water deficit by completely restricting irrigation. Seed germination was mostly affected by NaCl, but less by PEG in both species. E. bonariensis had a faster germination in all treatments and maintained a higher percentage of germination under the highest concentration of salt applied. Growth responses were similar in the two species, both being more affected by higher salt concentrations than by water deficit. The main differences in the responses of the two species to stress regard K+ and proline concentration. K+ in roots decreased under salt stress in E. sumatrensis, but remained constant in leaves, whereas in E. bonariensis increased in roots and leaves in salt-stressed plants. Proline concentration increased in all E. bonariensis plants under salt stress, but only in those under the highest salt concentration in E. sumatrensis. The results obtained indicate that the two species are relatively tolerant to water deficit and medium salinity but are susceptible to high NaCl concentrations.

TIP1;1 expression could modulate the recovery of stomatal opening during rehydration in Sorghum bicolor

Stomatal conductance (gs) takes longer to recover after drought when compared to leaf water potential or leaf water content (RWC). Aquaporins, known for transporting water through membranes, could modulate gs recovery. Using Sorghum bicolor, we tested whether members of the plasma membrane (PIP) and tonoplast (TIP) intrinsic aquaporin subfamilies could influence gs after a 20-day drought. Potted plants under soil field capacity (control), severe water deficit (SWD; 30% (m/m) soil water content), and progressive severe water deficit (PSWD; water withheld until maximum stress) were used. Soil (Ψsoil), predawn (ΨPD), and midday (ΨMD) leaf water potentials, photochemical, and gas exchange parameters were measured during drought and 12 days of recovery. After 17 days of drought, gs of SWD and PSWD was 4-times lower than control, and it took 6 days to recover. ΨPD, ΨMD, and RWC, however, recovered after 24 h. SbPIP1;2, SbPIP2;5, and SbTIP1;1 were all down-regulated on the day of maximum stress, but only SbTIP1;1 showed consistent alleviation of its down-regulation as gs recovered. SbTIP1;1 expression was positively correlated with gs, leaf transpiration, and hydraulic conductivity (KL), but only in SWD plants. The slow gs recovery seems to be associated with the alleviation of SbTIP1;1 down-regulation as rehydration progresses.

Drought specifically downregulates mineral nutrition: Plant ionomic content and associated gene expression.

One of the main limiting factors of plant yield is drought, and while the physiological responses to this environmental stress have been broadly described, research addressing its impact on mineral nutrition is scarce. Brassica napus and Triticum aestivum were subjected to moderate or severe water deficit, and their responses to drought were assessed by functional ionomic analysis, and derived calculation of the net uptake of 20 nutrients. While the uptake of most mineral nutrients decreased, Fe, Zn, Mn, and Mo uptake were impacted earlier and at a larger scale than most physiological parameters assessed (growth, ABA concentration, gas exchanges and photosynthetic activity). Additionally, in B. napus , the patterns of 183 differentially expressed genes in leaves related to the ionome (known ionomic genes, KIGs) or assumed to be involved in transport of a given nutrient were analyzed. This revealed three patterns of gene expression under drought consisting of up (transport of Cl and Co), down (transport of N, P, B, Mo, and Ni), or mixed levels (transport of S, Mg, K, Zn, Fe, Cu, or Mn) of regulation. The three patterns of gene regulations are discussed in relation to specific gene functions, changes of leaf ionomic composition and with consideration of the crosstalks that have been established between elements. It is suggested that the observed reduction in Fe uptake occurred via a specific response to drought, leading indirectly to reduced uptake of Zn and Mn, and these may be taken up by common transporters encoded by genes that were downregulated.