Water Relations Parameters Research Articles

Silicon Mitigates the Adverse Effect of Drought in Canola (Brassica napus l.) Through Promoting the Physiological and Antioxidants Activity

Drought is the major limiting factor for crops which reduces the growth and ultimately yield. However, silicon (Si) is considered one of the important elements for ameliorating adverse effect of abiotic stresses including drought also. To re-establish the previous evidence of Si, an experiment was carried out in a wire-house under pot-culture, where canola plants were grown under normal conditions (100% field capacity) and water deficit condition (40% field capacity). To know the ameliorative effect of silicon on drought-induced canola plants through promoting the physiological, growth, biochemical, and yield attributes of canola (Brassica napus L.); exogenous application of Si was done by two different methods i.e., through seed treatment (priming) before sowing and foliar spray at vegetative stage. For priming, seeds of canola were dipped for six hours in a 5 mM Si solution, whereas for foliar spray, three different levels of Si i.e., 2, 4 and 6 mM Si solution were applied at vegetative stage (after 40 days of seed emergence). Drought stress caused a substantial decrease in the parameters of water relations, and the uptake of various nutrients in canola plants. However, the application of Si significantly improved plants’ ability to withstand the drought stress through enhancing the uptake of Si in plants and also enhanced the activity of ascorbate peroxidase (APX), peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT). Data on, water potential, leaf water contents ratio and leaf pigments, (for example, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids), was positively influenced by applying Si under water deficit stress. Similarly, agronomic parameters such as seeds pod−1, seed weight and seed yield were also enhanced as a result of the Si application under drought condition. Among these application methods of Si, the foliar spray has been found more effective for alleviating the adverse effects of water deficit stress on canola plants. Therefore, the results of the present study revealed that foliar application of Si at the vegetative stage may be useful for ameliorating the adverse effect of drought; since Si promoted to maintain turgor pressure, antioxidants activity in plants and also improved the nutrient accumulation both under water stress and control condition.

Estrategias de tres especies arbustivas del Monte frente al estrés hídrico y su relevancia para la restauración

Knowing the different strategies of shrub species in arid zones allows selecting them to restore a specific site. According to Grime’s strategy scheme, plants of arid zones diverge into two main types: stress-tolerant, on the one hand, and ruderal, on the other. The objective of this study was to evaluate the adaptations to water stress of three shrub species (Atriplex lampa, Larrea cuneifolia and Senecio subulatus) widely distributed along the Monte region, as to be able to select them properly in future restoration projects. Three levels of water stress (watered when soil water content decreased by 50, 70 and 85%, control, moderate and severe water stress, respectively) were applied to 60 seedlings per species in a glasshouse study; pressure-volume curves were obtained and then, dry weight, tissue water relations parameters and ecophysiological indices associated with drought tolerance were measured. The strategies according to Grime were obtained using the StrateFy tool. Under severe water stress, the three species accumulated less dry matter and decreased their leaf area, and the growth of S. subulatus was the most affected. A. lampa and L. cuneifolia showed low leaf dry matter content, and A. lampa had the lowest specific leaf area. Through these foliar characters, the three species were classified as stress-tolerant according to Grime. Besides, A. lampa and L. cuneifolia perform osmotic adjustment under water stress conditions, while S. subulatus maintains high water potentials and does not modify its hydric parameters under these conditions. Therefore, S. subulatus has few mechanisms to cope with water stress and could be used to restore microsites where water accumulates, while A. lampa and L. cuneifolia, due to their stress-tolerant characteristics, are recommended for wide use to restore degraded areas of the Monte region.

Differences in Metabolic and Physiological Responses between Local and Widespread Grapevine Cultivars under Water Deficit Stress

Climate change forecasts suggest temperature increases and lower rainfall rates, both of which challenge viticulture, particularly in semi-arid areas where water availability is critical. In this scenario, the use of the genetic variability in grapevine varieties reported around the world represents an important strategy for the selection of climate-resilient cultivars. In this work, physiological and metabolomics analyses were conducted to compare the water deficit stress (WDS) responses of red and white, local and widespread grapevines cultivars. Leaf gas exchange, water use efficiency (WUE) and water relation parameters were determined in plants under well-watered and WDS conditions alongside assessment of the levels of foliar primary metabolites using gas-chromatography coupled to mass-spectrometry. Results denote that red and white local cultivars displayed more adapted physiological performance under WDS as compared to the widely-distributed ones. Multivariate analyses and specific changes in leaf primary metabolites indicate genotype-specific responses of local cultivars as compared to widespread ones. Differences in ascorbate-related and shikimate/phenylpropanoid metabolism could explain the better physiological performance under WDS in red local as compared to widespread cultivars. On the other hand, coordinated changes in respiratory- and stress-related sugars and amino acids could underlie the better WUE under WDS in the white local cultivar. All these results suggest several metabolic targets that could be useful as metabolic markers or for metabolic engineering in grapevine breeding programs to improve drought tolerance.

Salicylic acid-induced nitric oxide enhances arsenic toxicity tolerance in maize plants by upregulating the ascorbate-glutathione cycle and glyoxalase system

The role of nitric oxide (NO) in salicylic acid (SA)-induced tolerance to arsenic (As) stress in maize plants is not reported in the literature. Before starting As stress (AsS) treatments, SA (0.5 mM) was sprayed to the foliage of maize plants. Thereafter, AsV (0.1 mM as sodium hydrogen arsenate heptahydrate) stress (AsS) was initiated and during the stress period, sodium nitroprusside (SNP 0.1 mM), a NO donor, was sprayed individually or in combination with SA. Furthermore, cPTIO (0.1 mM) was also applied as a NO scavenger during the stress period. Arsenic stress led to significant reductions in plant growth, photosynthesis, water relation parameters and endogenous NO content, but it increased hydrogen peroxide, malondialdehyde, electrolyte leakage, methylglyoxal, proline, the activities of major antioxidant enzymes, and leaf and root As content. The combined treatment of SA+SNP was more effective to reverse oxidative stress related parameters and reduce the As content in both leaves and roots, with a concomitant increase in antioxidant defense system, the ascorbate-glutathione (AsA-GSH) cycle-related enzymes, glyoxalase system enzymes, plant growth, and photosynthetic traits. The beneficial effects of SA were completely abolished with cPTIO supply by blocking the NO synthesis in AsS-maize plants, indicating that NO effectively participated in SA-improved tolerance to AsS in maize plants.

GABA-Alleviated Oxidative Injury Induced by Salinity, Osmotic Stress and their Combination by Regulating Cellular and Molecular Signals in Rice.

This study was conducted in order to determine the effect of priming with γ-aminobutyric acid (GABA) at 0.5 mM on rice (Oryza sativa L.) seed germination under osmotic stress (OS) induced by polyethylene glycol (30 g/L PEG 6000); and salinity stress (S, 150 mM NaCl) and their combination (OS+S). Priming with GABA significantly alleviated the detrimental effects of OS, S and OS+S on seed germination and seedling growth. The photosynthetic system and water relation parameters were improved by GABA under stress. Priming treatment significantly increased the GABA content, sugars, protein, starch and glutathione reductase. GABA priming significantly reduced Na+ concentrations, proline, free radical and malonaldehyde and also significantly increased K+ concentration under the stress condition. Additionally, the activities of antioxidant enzymes, phenolic metabolism-related enzymes, detoxification-related enzymes and their transcription levels were improved by GABA priming under stress. In the GABA primed-plants, salinity stress alone resulted in an obvious increase in the expression level of Calcineurin B-like Protein-interacting protein Kinases (CIPKs) genes such as OsCIPK01, OsCIPK03, OsCIPK08 and OsCIPK15, and osmotic stress alone resulted in obvious increase in the expression of OsCIPK02, OsCIPK07 and OsCIPK09; and OS+S resulted in a significant up-regulation of OsCIPK12 and OsCIPK17. The results showed that salinity, osmotic stresses and their combination induced changes in cell ultra-morphology and cell cycle progression resulting in prolonged cell cycle development duration and inhibitory effects on rice seedlings growth. Hence, our findings suggested that the high tolerance to OS+S is closely associated with the capability of GABA priming to control the reactive oxygen species (ROS) level by inducing antioxidant enzymes, secondary metabolism and their transcription level. This knowledge provides new evidence for better understanding molecular mechanisms of GABA-regulating salinity and osmotic-combined stress tolerance during rice seed germination and development.

Characterization of the ecophysiological responses of three pomegranate cultivars to salinity

In order to understand photosynthetic responses of pomegranate plants (Punica granatum L.) to salinity, an experiment was conducted with three varieties, 'Mollar de Elche', 'Valenciana', and 'Wonderful', irrigated with seven salt concentrations (0, 40, 60, 80, 100, 120, and 140 mM NaCl). At the end of the experiment, parameters of gas exchange, chlorophyll fluorescence, water relations, and sugar and chloride concentrations were measured in leaves. As the concentration of NaCl increased, the concentration of Cl- in leaves was elevated, and the CO2 assimilation rate, stomatal conductance, variable fluorescence/maximum fluorescence ratio, PSII quantum yield, and total soluble sugars decreased. In 'Valenciana', the decrease of the net assimilation of CO2 could occur due to the closure of stomata, while in 'Mollar' and 'Wonderful', this was due to damage caused by Cl- toxicity. The study of carbohydrates also suggests a different behavior of carbon metabolism in the three varieties.

Physiological and biochemical attributes of bread wheat (Triticum aestivum L.) seedlings are influenced by foliar application of silicon and selenium under water deficit

In climate change scenario, drought is one of the serious environmental stress that limits agricultural productivity throughout the world. Silicon (Si) and selenium (Se) are known to effect physiological and biochemical processes under environmental stress. Therefore, this study was carried out to investigate the effects of Si and Se in alleviating the adversities of drought stress on physiological and biochemical processes in bread wheat seedlings. Treatments comprised of control (CK) (no drought stress nor Si and Se added), only drought [40% water holding capacity (WHC)], drought + Si (40% WHC with 40 mM Si), drought + Se (40% WHC with 40 mM Se), and drought + Si + Se (40% WHC + 40 mM Si + 40 mM Si). Plant material consisted of one bread wheat cultivar, Faislabad-2008. Data were collected for root shoot traits, physiological traits, and antioxidant enzymatic activities of shoot. Data analyses revealed that deficit irrigation inhibited the morphological attributes (root and shoot dry weight, root, and shoot length), water relation parameters, chlorophyll contents, net photosynthetic rate, transpiration rate, stomatal conductance, and CO2 concentration of wheat seedlings. On contrary, the foliage applied Si alone and in combination with Se under water deficit conditions stimulated plant growth and photosynthetic attributes, water relations, transpiration rate, and chlorophyll contents. In addition, an increase in antioxidants enzymatic activity was recorded under water deficit conditions, which was higher in wheat seedlings treated with combined application of Si and Se. Correlation analyses revealed strong association of antioxidant enzymatic activities with osmotic potential and turgor pressure. It is concluded from the study that foliage applied Si alone alleviates the negative impact of water deficit condition, while in combination with Se, both collectively found more effective in mitigating adverse effects of drought stress.

ElevatedCO2modulates the effects of drought and heat stress on plant water relations and grain yield in wheat

AbstractTo investigate the interactive effects of drought, heat and elevated atmosphericCO2concentration ([CO2]) on plant water relations and grain yield in wheat, two wheat cultivars with different drought tolerance (Gladius and Paragon) were grown under ambient and elevated [CO2], and were exposed to post‐anthesis drought and heat stress. The stomatal conductance, plant water relation parameters, abscisic acid concentration in leaf and spike, and grain yield components were examined. Both stress treatments and elevated [CO2] reduced the stomatal conductance, which resulted in lower leaf relative water content and leaf water potential. Drought induced a significant increase in leaf and spike abscisic acid concentrations, while elevated [CO2] showed no effect. At maturity, post‐anthesis drought and heat stress significantly decreased the grain yield by 21.3%–65.2%, while elevated [CO2] increased the grain yield by 20.8% in wheat, which was due to the changes of grain number per spike and thousand grain weight. This study suggested that the responses of plant water status and grain yield to extreme climatic events (heat and drought) can be influenced by the atmosphericCO2concentration.

Impact of drought stress on photosynthetic response, leaf water potential, and stem sap flow in two cultivars of bi-leader apple trees (Malus × domestica Borkh.)

ABSTRACT Photosynthetic responses and water relation of two apple cultivars, Hongro (medium-maturing) and Fuji (late-maturing), grafted on a single M.9 rootstock, were examined under drought stress conditions. Experimental bi-leader trees were grown in the field and were either well-irrigated or subjected to drought stress for 60 d. The photosynthetic responses and water relation parameters differed between the two cultivars. The net photosynthetic rate (Pn) in Hongro began to decrease at 15 d of drought treatment, while in Fuji this reduction occurred approximately 5 d later. Similarly, the Hongro cultivar in drought treatment showed a higher reduction in midday leaf water potential (ΨMD), stem sap flow, and hydraulic conductance (Ks) because of greater reduction of xylem vessel area, vessel density, and vessel diameter as compared to those in Fuji. As the ΨMD and stem sap flow decreased in drought stress treatment, the abscisic acid concentration in xylem sap increased; the increase was higher in Hongro than in Fuji. The changes in leaf morphological traits and reduction in total chlorophyll content were lower in Fuji than in Hongro. These results demonstrated that Fuji exhibited greater tolerance to water stress compared with Hongro.

The Effect of Different Mulch Types on Some Photosynthesis and Water Relation Parameters of Olive Cultivar ‘Manzanilla’ Under Water Stress Conditions

The Effect of Different Mulch Types on Some Photosynthesis and Water Relation Parameters of Olive Cultivar ‘Manzanilla’ Under Water Stress Conditions

Water relations and yield of wheat (Triticum aestivum L.) exposed to interactions of drought and fungal root diseases (Rhizoctonia and Pythium)

ABSTRACTA pot experiment investigated the effects of root diseases (Pythium and Rhizoctonia) under drought conditions at either tillering or anthesis stages on the water-use efficiency (WUE), water relations, and yield components of wheat cultivars Janz and Mulgara. The pathogens reduced transpiration in Janz during drought at tillering and in both cultivars during the period of recovery after drought at anthesis. However, the pathogens did not affect WUE. WUE did not differ between well-watered plants and those droughted at tillering but it was reduced by 80% by drought at anthesis. Un-infected plants of cultivar Janz subjected to drought at tillering had a higher total water potential (Ψw) and osmotic potential (Ψs) than diseased plants. However, Ψs of un-inoculated plants that were droughted at anthesis was lower than diseased plants in the period following anthesis. Yield components were significantly higher in well-watered than droughted plants and higher in cv. Mulgara than cv. Janz. The pathogens affected transpiration during tillering, but not at later stages, when roots developed beyond the inoculation point. Although the pathogens caused damage to the roots, the effects on water relations parameters were minor. This suggests that wheat can tolerate moderate levels of these root diseases under drought.

Evaluation of water relation parameters in vitis rootstocks with different drought tolerance and their effects on growth of a grafted cultivar

Knowledge of root hydraulic resistance will allow us to better understand water relations arising in the soil-plant-atmosphere continuum. These are the basis for better control of plant behaviour in the current environmental context that is more and more affected by global warming and problems related to increased drought frequency and duration. The objectives of this study were to determine how the growth of a cultivar changes in response to the drought tolerance of the rootstock used in Vitis grown in a semi-arid area and how the root hydraulic resistivity and root hydraulic conductivity change with increased transpiration when adopting a rootstock with a different drought tolerance.These experiments were carried out on intact plants of Gaglioppo grapevines grafted onto rootstocks of 779 P, a drought-tolerant American hybrid, and 420 A, a drought-susceptible American hybrid.Root hydraulic conductivity was significantly higher in the roots of 779 P than in the roots of 420 A. Stomatal conductance, net assimilation of CO2, leaf water potential, and relative water content were also higher in Gaglioppo grafted onto 779 P than that grafted onto 420 A. Leaf area, leaf dry weight, and specific leaf weight of Gaglioppo were also higher when grafted onto 779 P. Gaglioppo grapevine grafted onto 779 P showed superior growth and physiological performance.

Silicon influences growth and mycorrhizal responsiveness in strawberry plants.

Effect of silicon (Si) on the response of strawberry (Fragaria × ananassa var. Parus) plants to arbuscular mycorrhizal fungus (AMF) was studied under growth chamber conditions. Plants were grown in perlite irrigated with nutrient solution without (- Si) or with (+ Si) 3mmolL-1 Si (~ 84mg L-1 Si as Na2SiO3) in the absence (- AMF) or presence (+ AMF) of fungus. Dry matter production, root colonization rate, photosynthesis rate and water relation parameters were all improved by both Si and AMF, and the highest amounts were achieved by + Si + AMF treatment. Mycorrhizal effectiveness increased by Si treatment associated with higher Si concentration in the + AMF plants. Leaf concentrations of total soluble and cell wall-bound phenolics were increased by Si accompanied by the enhanced activity of phenylalanine ammonia lyase, but not polyphenol oxidase. Profile of phenolics compound revealed that gallic acid, caffeic acid, epicatechin, chlorogenic acid, ellagic acid and kaempferol increased by both Si and AMF treatments, while p-coumaric acid decreased. In addition to vegetative growth, both treatments improved fruit yield and its quality parameters. Our results showed that Si and AMF acted in a synergistic manner and improved growth and biochemical parameters in strawberry plants. However, the mechanism for Si-mediated increase of mycorrhizal effectiveness is not known, thereby needing further elucidation.

Influence of rootstock on pistachio (Pistacia vera L. cv Kerman) water relations

Selecting the rootstock in pistachio orchards is one of the most critical decisions, mainly in conditions of water scarcity. However, there are a few works that report the response of pistachio to water stress according to rootstock. Nowadays, UCB-I is one of the most important rootstock around the world. However, its commercial availability and high prices favour the selection of Pistacia terebinthus L. or Pistacia atlantica Desf. in some regions. The aim of this work is to study the water relations of these three rootstocks using cv Kerman as scion. Thirty pots, in the second year after budding, were subjected to a 28-days water stress period in outdoor conditions. Irrigation was stopped in the water stress treatments during all the 28 days period. The vegetative response was characterised at the end of the experiment. The diameter of the rootstock and scion, number of leaves and the percentage of leaves, trunk and root were measured. Along the experiment water relations parameters such as midday water potential and midday leaf conductance was measured. In order to compare the effect of rootstock and water stress pressure-volume curves were measured before and after the water stress period. Data of vegetative growth suggest that UCB-I was the rootstock less affected for water stress, because these data were not clearly affected. However, water relations parameters suggest that P. atlantica was the most resistant to water stress conditions, according to the results derivate from the pressure-volume curves. Possible mechanisms of response to water stress are discussed.

Relationships between water status and photosystem functionality in a chlorolichen and its isolated photobiont.

Drought tolerance was greater in the whole lichen than in its isolated photobiont. Cell turgor state has an influence on the functionality of photosynthetic process in lichens. Irreversible thermodynamics is widely used to describe the water relations of vascular plants. However, poikilohydrous organisms like lichens and aeroterrestrial microalgae have seldom been studied using this approach. Water relations of lichens are generally addressed without separate analysis of the mycobiont and photobiont, and only few studies have correlated changes in photosynthetic efficiency of dehydrating lichens to accurate measurements of their water potential components. We measured water potential isotherms and chlorophyll a fluorescence in the lichen Flavoparmelia caperata harvested in different seasons, as well as in its isolated photobiont, the green alga Trebouxia gelatinosa, either exposed to water stress cycles or fully hydrated. No significant seasonal trends were observed in lichen water relations parameters. Turgor loss point and osmotic potential of the whole thallus were significantly lower than those measured in the photobiont, while differences between the water stressed photobiont and controls were not significant. Dehydration-induced drop of F v/F m was correlated with turgor loss, revealing that the photosynthetic activity of lichens partly depends on their turgor level. We provided one of the first quantitative evidences of the influence that turgor status could exert on the functionality of photosynthetic processes in lichens.

Short-term physiological plasticity: Trade-off between drought and recovery responses in three Mediterranean Cistus species.

Short‐term physiological plasticity allows plants to thrive in highly variable environments such as the Mediterranean ecosystems. In such context, plants that maximize physiological performance under favorable conditions, such as Cistus spp., are generally reported to have a great cost in terms of plasticity (i.e., a high short‐term physiological plasticity) due to the severe reduction of physiological performance when stress factors occur. However, Cistus spp. also show a noticeable resilience ability in response to stress factors. We hypothesized that in Cistus species the short‐term physiological response to stress and that to subsequent recovery can show a positive trade‐off to offset the costs of the photosynthetic decline under drought. Gas exchange, chlorophyll fluorescence, and water relations were measured in C. salvifolius, C. monspeliensis, and C. creticus subsp. eriocephalus during an imposed experimental drought and subsequent recovery. Plants were grown outdoor in common garden conditions from seeds of different provenances. The short‐term physiological response to stress and that to recovery were quantified via phenotypic plasticity index (PIstress and PIrecovery, respectively). A linear regression analysis was used to identify the hypothesized trade‐off PIstress–PIrecovery. Accordingly, we found a positive trade‐off between PIstress and PIrecovery, which was consistent across species and provenances. This result contributes in explaining the profit, more than the cost, of a higher physiological plasticity in response to short‐term stress imposition for Cistus spp because the costs of a higher PIstress are payed back by an as much higher PIrecovery. The absence of leaf shedding during short‐term drought supports this view. The trade‐off well described the relative variations of gas exchange and water relation parameters. Moreover, the results were in accordance with the ecology of this species and provide the first evidence of a consistent trade‐off between the short‐term physiological responses to drought and recovery phases in Mediterranean species.

The Effect of Huanglongbing on Young Citrus Tree Water Use

Understanding the role of Huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus on citrus (Citrus sp.) water use is critical for determining if changes in water management of commercial citrus orchards affected by this disease is necessary. Reference evapotranspiration (ETo) is the most used methodology for irrigation scheduling, particularly in light of reports that indicate the lack of water for irrigation will become a major problem in many places around the world including Florida. The objectives of this study were to determine citrus tree water relationship [water use, sap flow, and stem water potential (Ψ)] as affected by ETo and HLB. The study was initiated on Jan. 2014 on two sweet orange (Citrus sinensis) cultivars included Hamlin and Valencia grown in a fine sandy soil texture (sandy, siliceous, and hyberthermic Arenic Alaquods) in a greenhouse. Twelve weighing lysimeters of each cultivar (six HLB-affected and six nonaffected trees) were used to determine selected water relation parameters. Results indicated a significant reduction in water use, Ψ, and sap flow for affected trees when compared with nonaffected trees. Citrus water use of healthy trees during the 2-year study was 31% and 27% greater than HLB-affected trees for ‘Hamlin’ and ‘Valencia’, respectively. Lower water use of HLB-affected trees resulted in 10% and 15% greater available soil water content than healthy ‘Hamlin’ and ‘Valencia’ trees, respectively. Therefore, reducing the water supply for HLB-affected trees than healthy trees may be a desirable practice that would lead to significant water savings.

Effect of potassium application in drought-stressed tobacco (Nicotiana rustica L.) plants: Comparison of root with foliar application

Effect of potassium (K) application through leaves (LA) or roots (RA) was studied in tobacco plants grown under K deficiency and drought stress conditions. Application of K was effective in improving the shoot growth only under drought conditions, whereas root biomass and length responded under both watering regimes. Under drought conditions, photosynthesis and transpiration activities increased upon K application leading to a reduced water use efficiency. Both RA and LA increased the leaf water potential, relative water content and turgor under both well-watered and drought conditions; RA was more effective than LA in the recovery of leaf turgor. Analyses of water relation parameters in different aged leaves showed lower susceptibility of the middle-aged leaves to both K deficiency and drought stresses than the upper and lower leaves; this phenomenon was accompanied by a more conservative control of water loss in the middle-aged leaves. In contrast, proline was accumulated in the young leaves, and K application increased it further. Although various organic osmolytes were accumulated under the combinative effect of K deficiency and drought stress, they did not exceed the amounts found in the control (well-watered +K) plants and were merely a result of the concentration effect. Collectively, our results revealed that the majority of leaf biochemical responses to drought stress are developmentally regulated processes. In addition, the alleviating effect of both RA and LA despite higher water loss indicated that an improved stomatal function upon K application allowed carbohydrates synthesis, thus, enhancing plant growth under water stress.

Improvement of broccoli sprouts ( Brassica oleracea L. var. italica) growth and quality by KCl seed priming and methyl jasmonate under salinity stress

Abstract Changes in the physiological and biochemical metabolism in broccoli sprouts treated with an elicitor (MeJA) and seed priming (KCl) under saline conditions were investigated in this study. Sprout germination, length, water relations, and root hydraulic conductivity, as well as glucosinolates and phenolic compounds, were determined in 10-d-old sprouts. The results show that salinity affected negatively all the parameters studied. Growth was only stimulated by seed priming under control and saline conditions. However, MeJA provided a positive response of the water relations parameters (osmotic and water potentials, and root hydraulic conductivity), and of the glucosinolate contents. Therefore, a possible complementarity with the treatments seed priming and MeJA that increased both growth and glucosinolate metabolism of the broccoli sprouts could provide the best sprouts management under salinity conditions.

Proliferating effect of radiolytically depolymerized carrageenan on physiological attributes, plant water relation parameters, essential oil production and active constituents of Cymbopogon flexuosus Steud. under drought stress.

Carrageenan has been proved as potent growth promoting substance in its depolymerized form. However, relatively little is known about its role in counteracting the adverse effects of drought stress on plants. In a pot experiment, lemongrass (Cymbopogon flexuosus Steud.), grown under different water stress regimes [(100% field capacity (FC), 80% FC and 60% FC)], was sprayed with 40, 80 and 120 mg L-1 of gamma irradiated carrageenan (ICA). Foliar application of ICA mitigated the harmful effects of drought stress to various extents and improved the biochemical characteristics, quality attributes and active constituents (citral and geraniol) of lemongrass significantly. Among the applied treatments, ICA-80 mg L-1 proved the best in alleviating detrimental effects of drought. However, drought stress (80 and 60% FC), irrespective of the growth stages, had an adverse impact on most of the studied attributes. Generally, 60% FC proved more deleterious than 80% FC. At 80% FC, application of ICA-80 mg L-1 elevated the essential oil (EO) content by 18.9 and 25%, citral content by 7.33 and 8.19% and geraniol content by 9.2 and 8.9% at 90 and 120 days after planting (DAP), respectively, as compared to the deionized-water (DW) spray treatment (80% FC+ DW). Whereas, at 60% FC, foliar application of 80 mg L-1 ICA significantly augmented the EO content by 15.4 and 17.8% and active constituents viz. citral and geraniol, by 5.01 and 5.62% and by 6.06 and 5.61% at 90 and 120 DAP, respectively, as compared to the control (water-spray treatment).