Effects Of Water Deficit Research Articles

Evidence of the very early effects of water deficit on cell division and expansion processes in tomato ovaries

Water deficit (WD) is known to reduce the final mass of tomato fruit. Despite the recorded positive relationship between final fruit mass and cell number, the latter being determined in the pre-anthesis period of ovary development, very few studies have investigated the effects of WD on ovary growth before anthesis. In this study, cell division and expansion in tomato ovaries (cv. H1311) were studied under two irrigation regimes: a control regime that maintained soil water content at field capacity and a WD regime with a 50% reduction in water supply compared to the control. The ovaries were sampled at 6 and 2 days before anthesis, at anthesis, at 2 and 5 days after anthesis, and at breaker stage. Effects of WD were already significant in the pre-anthesis period and the mesophyll layers contributed 96% of the final loss of fruit mass under WD. Overall, the results suggest that cell expansion was the predominant contributor to the loss of fruit mass, although cell number decreased at fruit scale. This was due to the relative contributions of the different layers to fruit cell number and mean cell volume, and to the specific patterns of development and response to WD occurring in each layer. This study provides important information on the regulation of fruit growth processes under WD and will help better predict the impact of it on fruit yield.

Delayed grape ripening by intermittent shading to counter global warming depends on carry-over effects and water deficit conditions

Grapevine phenology is continuously advancing due to global warming, exposing berry ripening to increasingly drier and hotter episodes that can dramatically affect yield and berry quality. This study aimed to analyse whether intermittent shading produced by panels placed over the plants can delay berry ripening to counter the impact of global warning on phenology. A two-year outdoor trial repeated on two batches of young potted grapevine (cv. Syrah) was conducted in Montpellier (South of France). Shading was created in a row using 2 m-wide horizontal panels placed 2.4 m above the ground. A moderate water deficit was also applied at the start of veraison to half the plants in both full sun (without panels) and shaded conditions to mimic usual field conditions. Variables related to budburst, flowering, veraison and sugar at harvest were analysed in all treatments. Although intermittent shading did not significantly modify air temperature within the canopy when cumulated over the growing season, the panels substantially delayed veraison by up to more than 30 days under well-watered conditions. The most marked phenological shifts were noted in the second year of treatment between flowering and veraison when carbon demand sharply increased during berry formation, suggesting there was a carry-over effect likely due to limited carbon assimilation. This was accompanied by sharp decreases in berry diameter and sugar content per berry at harvest. Higher berry growth and sugar loading were maintained when shading was combined with water deficit. However, the trigger effect of water deficit on veraison almost halved the phenological delay caused by the panels. Overall, a cooler period for ripening could be achieved with panels over the vines but at the expense of berry size and sugar amount in berries. It can be concluded that shading intensity and duration should be adapted to evaporative and soil water conditions to benefit from the phenological delay caused by panels, without altering production in the long term.

Foliar Applications of ZnO and Its Nanoparticles Increase Safflower (Carthamus tinctorius L.) Growth and Yield under Water Stress

Foliar application or minerals is a methodology to promote growth and/or yield and to protect plants against different kinds of stresses. Currently there is a great interest in evaluating the effect of nanoparticles for enhancing the effect of these treatments. This study was performed to evaluate and compare the effect of foliar application of zinc oxide (ZnO) and zinc oxide nanoparticles (ZnO-NPs) on the growth and yield of safflower under different irrigation regimes. Foliar applications of ZnO in all concentrations (4, 6, 8, 10, 12, and 14 g L−1) led to an increase in biomass yield, number of capitula per plant, number of seeds per capitulum, and grain yield of plants compared with control plants. The maximum increase in the studied traits was obtained with a ZnO concentration of 6, 8, and 10 g L−1. In a second round of experiments, we observed the effect of nanoparticles and found that spraying with ZnO and ZnO-NPs at a concentration of 10 g L−1 may ameliorate the deleterious effects of water deficit. The results of the present study support the idea that foliar application of ZnO improves safflower yield, especially under drought stress, and showed that using of nanoparticles increases the efficiency of the application.

Effect of Water Stress Induced by Polyethylene Glycol on Growth, Proline Accumulation in Agave americana L.

The effect of water deficit was determined on both in vitro and soil seedling as well as in cells in suspension of Agave americana L. In order to do the establishment of cells, the formation of callus was induced; for it two auxins were evaluated: 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-mino-3,5,6-trichloropicolinic acid (picloram) at three concentrations (0.25, 0.5 and 0.75 mg L−1) in three explants (leaf, root and meristems) cultured in MS semisolid medium. The callogenesis response was related to the type and section of the explant, as well as the regulator used, and a cell suspension was established using 0.5 mg L−1 naphthaleneacetic acid (NAA) + 0.5 mg L−1 Benzylaminopurine (BAP). Seedlings were exposed to polyethyleneglycol (15% and 30% w/v) with a water potential of −0.87 and −2.67 MPa, respectively, under soil conditions. Water stress was applied through restricted irrigation. Fresh weight, root system growth, and chlorophyll concentration were some of the parameters that were affected by the effect of water deficit on A. americana L. Chlorophyll concentration values were significantly decreased by 15 at 30% PEG (19.6 SPAD units) compared to the control treatment. In in vitro plants, the highest concentration of proline was found in the roots, being the treatment with 30% polyethylene glycol where the highest concentration of this osmoregulator was obtained (62.5 mg g−1 DW). Under restricted irrigation conditions, an increase in proline concentration was observed both in the aerial part (2.2 µg 100 g−1 DW) and in the root system (1.8 µg 100 g−1 DW). However, the concentrations found were approximately ten times greater, less than those found under in vitro conditions. Therefore, the accumulation of proline can be considered an indicator of stress in Agave Americana L. growth in vitro.

Effect of Water Deficit on the Productivity of Four Bread Wheat Cultivars under Calcareous Soil Conditions in Egypt

Effect of Water Deficit on the Productivity of Four Bread Wheat Cultivars under Calcareous Soil Conditions in Egypt

O CO2 elevado induz a regulação negativa da fotossíntese e alivia o efeito do déficit hídrico em Ceiba pentandra (Malvaceae)

ABSTRACT The simultaneous effect of elevated CO2 concentration and drought on trees is still under investigation in the Amazon. We evaluated the effect of CO2 levels (400 and 800 ppm) and water regimes (50% and 100% soil field capacity) on photosynthetic traits, chlorophyll fluorescence, and total biomass accumulation in Ceiba pentandra. In well-watered plants, light-saturated photosynthesis (PN-sat) increased in plants exposed to elevated CO2, but both PN-sat and stomatal conductance decreased in response to water deficit. The maximum carboxylation rate of Rubisco declined under elevated CO2, which indicates down-regulation of photosynthesis at elevated CO2. The Fv/Fm ratio was not affected by treatments. Notwithstanding, total plant biomass and leaf area were reduced by 34-37% under water deficit, but they were not affected by CO2 levels. The PN-sat values measured in well-irrigated plants at ambient CO2 were similar to those observed in plants subjected to elevated CO2 and water deficit (p = 0.26). We concluded that the effect of water deficit on PN-sat was mitigated by elevated CO2. These results suggest that the increase of atmospheric CO2 concentrations associated to climate changes can at least partly offset the negative effect of drought in this multiuse and widely distributed species.

Yield response factor (Ky) and initial growth in black pepper in a tropical environment

Black pepper is widely produced in Brazil, though there are few studies related to its water requirements and the effects of water deficit (WD) applied under tropical conditions. The growth, sensitivity to WD, and first-year productivity of irrigated plants from the Bragantina cultivar were evaluated, employing an irrigation system with automatic management. The plants were cultivated in plastic pots installed in the field for 391 days using emitters with different flow rates (2.2 [T1], 3.3 [T2], 4.3 [T3], and 5.3 L h–1 [T4 – control]). Fresh weight of the leaves, stems, and shoots, and dry weight of the leaves, stem, roots, and shoots as well as the total dry weight of the plant, were evaluated. Productivity was determined by evaluating the grains and spikes from a single harvest. Yield results and the actual versus maximum evapotranspiration rate for the entire growing season was used for calculating the Ky coefficient. Despite 1,346 mm of rainfall, the irrigation system was activated 165 times, distributing a mean volume of 19.0 (T1), 28.5 (T2), 37.1 (T3), and 45.8 L per plant (control). All traits were negatively affected by the WD, and the Ky values obtained (from 1.72 to 2.96) indicate the high sensitivity of black pepper to WD. In general, the spikes produced with at least 81 % of the crop water demand were larger and more numerous than those subjected to inferior treatments. WD occurring during the flowering stage severely hampers the size, weight, and quality of the spikes and grains of black pepper.

Effect of water deficit on water status and growth of five tropical species used in urban forestry

Due to the urban environment urban trees must deal with drier and hotter than in rural areas. Knowing the water consumption of each species and the indicators of water deficit is useful to decide the frequency and volume of irrigation and to select species according to the microclimate of the location. To determine approximately the irrigation frequency and to identify physiological variables that indicate water stress, it was carried out an experiment in which five tropical species (Citharexylum montanum M., Citharexylum sulcatum M., Caesalpinia spinosa K., Inga edulis M. and Retrophyllum rospigliosii P.) were subjected to water deficit. After a month of planting, eight trees per species were subjected to four treatments: control treatment (volumetric water content higher than 45% (TC)), the volumetric water content of 20% (VM20), fifteen and thirty days after the soil had reached VM20 (T15 and T30, respectively). In trees with similar height, it was found that the descending order of water consumption was I. edulis, C. montanum, C. spinosa, C. sulcatum, R. rospigliosii and that the best indicator of water deficit was the stem water potential. In general, volumetric moisture of soil of 20% was a suitable threshold to decide when irrigating regardless of the species. Deeming the effect of the treatments on the growth of the assessed species, T30 diminished severely the growth by 50% in comparison to the control, except for C. sulcatum in which there were no significant differences.

Calcium pyruvate in the attenuation of the water deficit on the agro-industrial quality of ratoon sugarcane.

Sugarcane is one of the largest agricultural commodities when considering the export volume and the number of jobs generated. Sugarcane production in the Brazilian Northeast region is generally low due to several factors, including the irregular rainfall distribution, which highlights the importance of studies aimed at mitigating the deleterious effects of water stress. In this scenario, this study aimed to evaluate calcium pyruvate as a water deficit attenuator on the agro-industrial quality of sugarcane in the second cycle of cultivation. The experiment was conducted out under greenhouse conditions of the Federal University of Campina Grande, where five sugarcane commercial genotypes tested (G1- RB863129, G2- RB92579, G3- RB962962, G4- RB021754, and G5- RB041443) and three irrigation management strategies (E1- full irrigation, E2- water deficit with application of 30 mM of calcium pyruvate, and E3- water deficit without calcium pyruvate application), distributed in randomized blocks in 5 × 3 factorial arrangement with three replications. The RB021754 genotype under water deficit and without foliar application of calcium pyruvate increased the fiber content (13.2%) and the sugarcane moist cake weight (143.5 g). The effects of water deficit in sugarcane genotypes are attenuated by the exogenous application of 30 mM of calcium pyruvate, with benefits on the polarized sucrose content, apparent sucrose content of the juice, soluble solids content, purity, corrected cane POL, total recoverable sugars, and stem mass in relation to plants under water deficit without calcium pyruvate application.

Heat tolerance changes of an intact semi-desert cryptobiotic crust during desiccation dominated by Didymodon species

The thermal stability of photosysthetic apparatus was examined under different (light and desiccation) treatments in the mosses (Didymodon luridus Hornsch, Didymodon nicholsonii Culm) dominated intact semi-desert cryptobiotic crusts. The relatively low temperature tolerance measured in default state (non energised thylakoids at full turgor) in the samples was inadequate to survive the thermal conditions of the original habitat. This was also manifested in the temperature sensitivity of optimal quantum yield (Fv/Fm) measured in dark-adapted state. The temperature dependence of the steady-state level of fluorescence, measured in light-adapted state, indicated a moderate decrease in heat sensitivity of PS II which was further enhanced by moderate water deficit. Moreover, a considerable water loss extremely increased the thermal stability of PS II in both dark and light-adapted states. Temperature dependence of the different quenching parameters suggests that in light-adapted state, the secondary effects of low lumen pH may protect against both temperature stress and water loss: i.e., it is likely that protection against the effects of light, temperature, and water deficit can be partly based on common bases. At very high temperatures the thermal damage of the oxygen-evolving complex is unlikely to be avoided, however, under continuous actinic light, the variable fluorescence (Fm’-Fs=AF) was partially recovered even above the critical temperature values of the Fs-T curves. This indicates the partial restoration of the electron donation of the PS II reaction centres by alternative electron donors. These changes in heat tolerance play a significant role to tolerate the effects of daily changing of the ecological factors in the habitat and it has a pronounced ecological significance and partly explains the survival of the examined crusts even under extreme semi-desert conditions.

Shading minimizes the effects of water deficit in Campomanesia xanthocarpa (Mart.) O. Berg seedlings.

The objective of this study was to evaluate the activity of antioxidant enzymes, the functioning of the photosystem II and quality of C. xanthocarpa seedlings cultivated under intermittent water deficit and shading levels and the influence of shading on recovery potential after suspension of the stress conditions. The seedlings were subjected to three levels of shading (0, 30, and 70%), six periods of evaluation (start: 0 days; 1st and 2nd photosynthesis zero: 1st and 2nd P0; 1st and 2nd recovery: 1stand 2nd REC; and END), and two forms of irrigation (control: periodically irrigated to maintain 70% substrate water retention capacity, and intermittent irrigation: suspension of irrigation). The plants subjected to intermittent irrigation conditions at 0% shading showed a reduction in water potential (Ψw) and potential quantum efficiency of photosystem II (Fv/Fm) and maximum efficiency of the photochemical process (Fv/F0) and an increase in basal quantum production of the non-photochemical processes (F0/Fm). Superoxide dismutase (SOD) activity was higher in the leaves than in the roots. The C. xanthocarpa is a species sensitive to water deficit but presents strategies to adapt to an environment under temporary water restriction, which are more temporary are most efficient under shading. The seedlings with water deficit at all levels of shading exhibited higher protective antioxidant activity and lower quality at 0% shading. The shading minimizes prevents permanent damage to the photosystem II and after the re-irrigation, the evaluated characteristics showed recovery with respect to the control group, except POD and SOD activities in the leaves.

Physiological and transcriptome analyses of the effects of excessive water deficit on malic acid accumulation in apple.

Acidity is a determinant of the organoleptic quality of apple, whereas its regulatory mechanism under water stress remains obscure. Fruit from apple 'Yanfu 3' of Fuji trees grown under normal water irrigation (CK), excessive water deficit treatment (DRT) and excessive water irrigation treatment (WAT) were sampled at 85, 100, 115, 130, 145, 160 and 175days after full bloom designated stages S1, S2, S3, S4, S5, S6 and S7, respectively. DRT treatment reduced the individual fruit weight and fruit moisture content, and increased fruit firmness. The malate content of DRT treatment was higher than that of CK and WAT from stages S1 to S7. RNA sequencing (RNA-seq) analysis of the transcriptome at stages S4, S6 and S7 indicated that malate anabolism was associated with cysteine and methionine, auxin signaling, glyoxylate and dicarboxylate and pyruvate metabolism. Overexpression of MdPEPC4 increased the malate content in apple calli induced by 4% PEG. Our study provides novel insights into the effects of water stress on the molecular mechanism underlying apple fruit acidity.

Chitosan Induces Sorghum Tolerance to Water Deficits by Positively Regulating Photosynthesis and the Production of Primary Metabolites, Osmoregulators, and Antioxidants

Current climate change scenarios require strategies that mitigate the effects of water deficits. Given that chitosan stimulates induced resistance responses, we tested the hypothesis that foliar application of this polysaccharide can have positive effects on the primary metabolite, antioxidant, and osmoregulatory metabolisms of sorghum, mitigating the effects of water deficit on grain yield. Sorghum plants were cultivated under either irrigated or water-deficit conditions and were either treated or untreated with chitosan, and we assessed the following responses: water potential, gas exchange, nutritional status, biosynthesis of primary and osmoregulatory metabolites, the activity of the antioxidant system constituents, and hydrogen peroxide and malondialdehyde contents. An active methodology was used to impose water stress on plants grown in pots with 20 kg of soil, 06 replications per treatment. Sorghum plants subjected to water deficit that were treated with chitosan exhibited higher stomatal conductance and transpiration than the untreated plants. Water restriction reduced the nutrient contents of leaves, but in the irrigated plants, chitosan treatment increased the tissue contents of certain nutrients and leaf concentrations of total proteins and total amino acids. In the plants under water-deficit conditions that were treated with chitosan, an elevated photosynthetic rate contributed to an increase in carbohydrate accumulation and a higher production of panicle and grain dry biomass compared with the untreated plants. The activity of catalase and ascorbate peroxidase also increased in response to chitosan. Overall, chitosan was effective in enhancing the water deficit tolerance of sorghum plants cultivated under water-deficit conditions by 57%. With this work, we generate perspectives for studies focusing on the development of water-deficit-resistant sorghum lineages, by means of chitosan elicitation.

Effect of water deficit of Ultisols, Entisols, Spodosols, and Histosols on oil palm productivity in Central Kalimantan

The same rainfall can cause different degrees of water stress depending on soil type, so the production response shown by plants can be different. This study is essential for growers, especially in predicting oil palm production based on water deficit for each soil type. The study was conducted on oil palm plantations in Central Kalimantan, Indonesia, with four soil types in 1,446.15 ha (40 blocks). The source of data collected from oil palm plantations included bunch number, average bunch weight, rainfall, and soil physical and chemical properties for the last 15 years (2007 - 2021). This experimental study used a two-stage cluster sampling method. The results showed that the best productivity, bunch number, and average bunch weight were found on Ultisols. The four soil types tested showed the same annual production distribution dynamic, but the response rate from each soil type showed differences. Entisols and Spodosols were more prone to drought stress due to water deficit than Ultisols and Histosols because of the differences in soil texture. Water deficit causes a decrease in oil palm productivity by 5 - 22% in the first year (Ultisols 12 - 22%; Entisols 12 - 22%; Spodosols 7 - 19%; Histosols 5 - 15%) and 1 - 8% in the second year (Ultisols 3 - 7%; Entisols 2 - 4%; Spodosols 5 - 8%; Histosols 1 - 5%) compared to previous years production. A decrease in oil palm productivity occurs at 3 - 5 months (bunch failure phase), 1 year (abortion sensitive phase), and 2 - 2.5 years (sex differentiation phase) after a water deficit appears.

Effects of Moderate Water Deficit on the Accumulation and Translocation of Stem Non-Structural Carbohydrates, Yield and Yield Components in a Sink-Limited Rice Variety Under Elevated CO2 Concentration

Effects of Moderate Water Deficit on the Accumulation and Translocation of Stem Non-Structural Carbohydrates, Yield and Yield Components in a Sink-Limited Rice Variety Under Elevated CO2 Concentration

Responses of grapevines to planting density and training systems in semiarid environments

Aim. To investigate the physiological and agrobiological responses of grapevines on different systems of training systems in row plantations depending on the planting density and the possibility of adjusting plants for non-irri- gated crop cultivation under cold semiarid climate. Methods. The field two-way experiment of 2 × 4 was applied to study the effect of two planting density variants (3 × 1.5 m; 3 × 1 m) and four vine training systems (when the horizontal cordon is located at the height of 0.4 m, 0.8 m, 1.2 m, 1.6 m) on the parameters of the leaf area, leaf index, water loss through transpiration, activity of the photosynthetic apparatus of leaves and the yield of Zahrei wine grape cultivar (Vitis vinifera L.). The experiment data were processed using the analysis of variance. Results. The increase in the density of vine row plantations per area units from 3 × 1.5 m to 3 × 1 m enlarges the total leaf area, the exposed leaf area, water loss through transpiration, and yield weight, but these indices decrease in the evaluations per plant. The responses of grapevine to the training systems are similar and independent from the ex- perimental variants of planting density. At the height of the cordon of 0.4 and 0.8 m, the vertical shoot positioning enhances the potential of the photosynthetic capacity of the plantations, but this potential is realized only during the years with lower water deficit for plants. Free-growing shootings on the cordons, located at the height of 1.2 m, form the canopy architecture with relatively low water loss through transpiration which has a positive effect on the activity of the photosynthetic apparatus and yield, especially in dry years. The downward shoot positioning on the cordons of 1.6 m decreases the leaf area of the vines and creates the canopy architecture with increased transpiration which enhances the effect of the water deficit and has a negative effect on the productivity of plants. Conclusions. The agronomic methods of planting and training systems for grapevines ensure the management of the character of spatial shoot location, the formation of certain canopy architecture, and setting the parameters of the leaf area; their optimization mitigates the negative effect of water deficit and provides for adapting the plants for non-irrigated crops under semiarid climate. The positive effect of compacting plantations on crop yield was determined without irrigation in semiarid environments. The variant of planting density of 3 × 1 m decreases the yield on the vines on average by 12.1–31.0 %, as compared to the variant of 3 × 1.5 m. Yet, more dense plantations are remarkable for their yield, which is 18.5–61.3 % higher depending on the training system for vines. Under dry conditions, the most efficient system is the training system with the formation of the horizontal cordon at the height of 1.2 m and free-growing shoots. The system optimizes the leaf area density, and forms the canopy architecture with rather low water loss through transpiration which has a positive effect on the activity of the photosynthetic apparatus of leaves during droughts. Under free growth, the yield of the plantations increases by 4.3–12.3 % on average as compared to the vertical shoot positioning and by 21.3 % – under their downward positioning.

Diaspore dispersal season influences root growth and seed traits, but not germination responses, of sympatric Piper species in a seasonal forest.

Seeds may differ in terms of dormancy, longevity, sensitivity to desiccation and dry mass, according to the timing (dry season/rainy season) of diaspore dispersal. In addition, seasonal variations in temperature and water availability can act as signals of the season during seed development, influencing germination responses and root growth. We evaluated the effects of temperature variations and water availability on germination parameters, root growth and seed traits of four coexisting Piper species in seasonal vegetation that differed in diaspore dispersal timing. Eight temperature treatments (15, 20, 23, 25, 28, 30, 35 °C, and alternate 30 °C-20 °C) and four induced water potentials (0, -0.3, -0.6 and -1.2 MPa) were used. The parameters germination onset, germination percentage (G%), mean germination time (MGT), root elongation, seed longevity during ex situ storage and dry mass of seeds were evaluated. Germination responses observed were independent of the diaspore dispersal timing, such as variations in germination onset, G% and MGT, both in temperature and water availability treatments. In contrast, root elongation, longevity and dry mass of seeds varied according to the time of diaspore dispersal. Our results corroborate the hypothesis that the timing of diaspore dispersal is an important factor in controlling the initial development of seedlings in seasonal vegetation, but not in germination responses. The predominance of negative effects of temperature increases and water deficit on root growth shows that the initial stages of plant development can be strongly impacted by these environmental factors.

Simultaneous effect of water deficit and mating systems in fennel (Foeniculum vulgare mill.): Genetics of phytochemical compositions and drought tolerance

Limited information is available on the impact of deliberate selfing compared with open-pollination and its interaction with water deficit on productivity and phytochemical constituents of essential oil in fennel (Foeniculum vulgare Mill.) and also the genetic analysis of traits. During this research, 21 selfed (S1) and 42 open-pollinated (OP) progenies of fennel developed in 2017–18 were evaluated in the field under well-watered and water deficit conditions in two years (2019 and 2020) for phytochemical and productivity traits. GC–MS analysis revealed that among the eight different compounds in the essential oil, trans-anethole, fenchone, estragole, and limonene were found to be the main constituents. Water deficit greatly decreased grain yield and essential oil content, α-pinene, trans-anethole, and anisaldehyde; while significantly increased β-myrcene, limonene, γ-terpinene, fenchone, and estragole, in both populations. Compared with open-pollination, selfing reduced the mean performance of seed and essential oil yield, β-myrcene, and limonene under normal and water deficit conditions, and α-pinene under normal condition, demonstrating the effects of inbreeding on these traits. The relationship between γ-terpinene and anisaldehyde was positive in the S1 population; while in the OP population, there was significant and negative association between these two constituents. The genetic analysis of traits indicated that additive gene action played an important role in controlling most of the traits, but that both additive and non-additive gene effects played a role in the genetic control of grain yield; indicating that selection based on an index may be more useful for improvement of grain yield in recurrent selection programs.

Salicylic acid and thiourea mitigate salinity and drought stress in wheat (Triticum aestivum)

Water and salinity stresses are the major environmental concerns limiting crop production, particularly in arid and semi-arid ecologies. Focused research is required to develop mitigating strategies to manage such stresses. Application of plant-bioregulators (PBRs) may be an effective option to manage water and salinity stresses. Therefore, a field experiment was conducted during 2016–17 and 2017–18 at semi-arid saline site of NW (north-western) India to assess the effectiveness of salicylic acid and thiourea in easing out the adverse effect of variable water deficit and irrigation water salinity regimes. Increasing water deficit and its salinity significantly (P<0.001) reduced all the studied growth parameters, viz. plant height, crop stand, no. of tillers, leaf area index and relative growth rate; and yield attributes like no. of effective tillers, spike length, grains/spike, grain weight/spike, 1000-grain weight, specific weight. Application of either salicylic acid or thiourea significantly improved growth parameters in comparison to control and thiourea proved more effective. Thiourea application improved grain yield by 3.96 and 17.36%, biological yield by 4.21 and 14.82%, effective no. of tillers by 3.77 and 11.91%, weight/spike by 2.83 and 15.17%, 1000-grain weight by 3.72 and 12.66% and specific weight by 2.04 and 8.84% compared to salicylic acid and control, respectively. This might be due to better nutrient uptake, water relations, enhanced CO2 fixation and effective partitioning of assimilates. Thus, thiourea and salicylic acid application in wheat found better as compared to control under saline water stress.

A root functional-structural model allows assessment of the effects of water deficit on water and solute transport parameters.

Root water uptake is driven by a combination of hydrostatic and osmotic forces. Water transport was characterized in primary roots of maize seedlings grown hydroponically under standard and water deficit (WD) conditions, as induced by addition of 150 g l-1 polyethylene glycol 8000 (water potential= -0.336 MPa). Flow measurements were performed using the pressure chamber technique in intact roots or on progressively cut root system architectures. To account for the concomitant transport of water and solutes in roots under WD, we developed within realistic root system architectures a hydraulic tree model integrating both solute pumping and leak. This model explains the high spontaneous sap exudation of roots grown in standard conditions, the non-linearity of pressure-flow relationships, and negative fluxes observed under WD conditions at low external hydrostatic pressure. The model also reveals the heterogeneity of driving forces and elementary radial flows throughout the root system architecture, and how this heterogeneity depends on both plant treatment and water transport mode. The full set of flow measurement data obtained from individual roots grown under standard or WD conditions was used in an inverse modeling approach to determine their respective radial and axial hydraulic conductivities. This approach allows resolution of the dramatic effects of WD on these two components.