Tolerance To Water Deficit Research Articles

Foliar application of potassium nitrate induces tolerance to water deficit in pre-flowering sorghum plants

The objective of this study was to evaluate the the ability of foliar application of potassium nitrate (KNO3) to induce water deficit tolerance in sorghum plants (Sorghum bicolor cv. P898012) subjected to water deficit at pre-flowering. The experiment was conducted under greenhouse conditions with 4 treatments: field capacity (FC), water deficit (WD), field capacity + KNO3 (FC + KNO3), and water deficit + KNO3 (WD + KNO3). Two foliar applications of 3% (m/v) KNO3 were made, the first on day zero of stress and the second on the fifth day. All analyses were performed after 12 days of stress (end of stress). Foliar application of KNO3 to irrigated plants led to increases in relative chlorophyll content, photosynthetic rate, stomatal conductance, transpiration, and carboxylation efficiency. It also induced increases in leaf concentrations of P, Mg, S, Cu, and Fe, in addition to height growth. Under water deficit conditions, plants treated with KNO3 presented higher relative chlorophyll content, leaf area, photosynthetic rate, stomatal conductance, transpiration, carboxylation efficiency, and higher levels of P, K, Mg, S, Cu, and Fe than those not treated with KNO3. The morphometry of the root system was not altered by the treatments. In addition, plants treated with KNO3 under water deficit conditions showed higher growth and a grain yield 32.2% higher than those that did not receive KNO3. These results demonstrated that KNO3 applied to the leaves induced water deficit tolerance in sorghum plants subjected to severe water stress at pre-flowering.

Evaluation of the Morpho-Physiological, Biochemical and Molecular Responses of Contrasting Medicago truncatula Lines under Water Deficit Stress.

Medicago truncatula is a forage crop of choice for farmers, and it is a model species for molecular research. The growth and development and subsequent yields are limited by water availability mainly in arid and semi-arid regions. Our study aims to evaluate the morpho-physiological, biochemical and molecular responses to water deficit stress in four lines (TN6.18, JA17, TN1.11 and A10) of M. truncatula. The results showed that the treatment factor explained the majority of the variation for the measured traits. It appeared that the line A10 was the most sensitive and therefore adversely affected by water deficit stress, which reduced its growth and yield parameters, whereas the tolerant line TN6.18 exhibited the highest root biomass production, a significantly higher increase in its total protein and soluble sugar contents, and lower levels of lipid peroxidation with greater cell membrane integrity. The expression analysis of the DREB1B gene using RT-qPCR revealed a tissue-differential expression in the four lines under osmotic stress, with a higher induction rate in roots of TN6.18 and JA17 than in A10 roots, suggesting a key role for DREB1B in water deficit tolerance in M. truncatula.

Water deficit induced physiological and amino acid responses in some rice varieties using NMR‐metabolic analysis

AbstractDeficit irrigation (DI) is a choice made by producers to improve water productivity and might be highly preferred in future production programs in arid regions. Identifying DI‐tolerant cultivars will be critical to improve rice (Oryza sativa L.) productivity under the future climate change conditions. Nuclear magnetic resonance (NMR)‐based metabolomics is a recent technique that has received less attention so far and can be used to compare genetic differences in DI tolerance. For this purpose, field experiments were carried out during two successive summer seasons in Egypt to compare genetic differences for water deficit tolerance in seven rice genotypes using NMR technique. The genotypes Azucena and IRAT 170 achieved the best values of water productivity (WP) under DI, recording 1.79 and 0.99 kg m–3 respectively, confirming their suitability in the water deficit breeding program to produce new promising lines and to keep yield potential stable under climate change conditions. The PLS‐DA of 1H‐NMR spectra showed a clear separation between genotypes under both full irrigation (FI) and DI conditions. Quantitative analysis showed that sucrose, threonine, glutamate, and allantoin were accumulated at DI when compared to FI conditions, and these metabolite compounds may be closely related to DI conditions. Tryptophan, as an aromatic amino acid, has increased across cultivars, most dramatically in Azucena and IRAT 170. Tyrosine and phenylalanine also increased in Azucena and IRAT 170, but not as dramatically as tryptophan. The rice genotypes Azucena and IRAT 170 could be successfully recommended for higher yields and quality under DI conditions.

Transcriptional profiling and physiological responses reveal new insights into drought tolerance in a semiarid adapted species, Anacardium occidentale.

Water stress affects plant performance at various organisational levels, from morphological to molecular, with a drastic drop in crop yield. Integrative studies involving transcriptomics and physiological data in recognized tolerant species are appropriate strategies to identify and understand molecular and functional processes related to water deficit tolerance. The cashew tree (Anacardium occidentale) is a species naturally adapted to environments with low water availability associated with adverse conditions such as heat, high radiation and salinity. We used an integrative strategy, combining classical physiological measurements with high throughput RNA-seq to understand the main adaptive mechanisms of cashew to water deficit followed by recovery. Physiological analyses indicate that young cashew plants display typical isohydric behaviour. They first exhibit rapid stomatal closure, followed by CO2 assimilation, thus preserving the relative water content, membrane integrity and photosystem II activity. Differential expression was observed in 1733 genes from plant leaves exposed to water deficit stress for 26days. Among them, 705 were upregulated and 1028 were downregulated. After rewatering, 1330 (76.7%) genes returned to their basal expression level. Transcriptional, combined with physiological data, reveal that cashew plants display high phenotypic plasticity and resilience to acute water deficit, and do not activate senescence pathways. A series of genes/pathways and processes involved with drought tolerance in cashew are evidenced, particularly in carbon metabolism, photosynthesis and chloroplast homeostasis.

Characterization of Dynamic Regulatory Gene and Protein Networks in Wheat Roots Upon Perceiving Water Deficit Through Comparative Transcriptomics Survey.

A well-developed root system benefits host plants by optimizing water absorption and nutrient uptake and thereby increases plant productivity. In this study we have characterized the root transcriptome using RNA-seq and subsequential functional analysis in a set of drought tolerant and susceptible genotypes. The goal of the study was to elucidate and characterize water deficit-responsive genes in wheat landraces that had been through long-term field and biochemical screening for drought tolerance. The results confirm genotype differences in water-deficit tolerance in line with earlier results from field trials. The transcriptomics survey highlighted a total of 14,187 differentially expressed genes (DEGs) that responded to water deficit. The characterization of these genes shows that all chromosomes contribute to water-deficit tolerance, but to different degrees, and the B genome showed higher involvement than the A and D genomes. The DEGs were mainly mapped to flavonoid, phenylpropanoid, and diterpenoid biosynthesis pathways, as well as glutathione metabolism and hormone signaling. Furthermore, extracellular region, apoplast, cell periphery, and external encapsulating structure were the main water deficit-responsive cellular components in roots. A total of 1,377 DEGs were also predicted to function as transcription factors (TFs) from different families regulating downstream cascades. TFs from the AP2/ERF-ERF, MYB-related, B3, WRKY, Tify, and NAC families were the main genotype-specific regulatory factors. To further characterize the dynamic biosynthetic pathways, protein-protein interaction (PPI) networks were constructed using significant KEGG proteins and putative TFs. In PPIs, enzymes from the CYP450, TaABA8OH2, PAL, and GST families play important roles in water-deficit tolerance in connection with MYB13-1, MADS-box, and NAC transcription factors.

Evaluation of Calcium Application Methods on Delaying Plant Wilting under Water Deficit in Bedding Plants

Floriculture crops can lose their aesthetic quality due to water deficit during postproduction. Calcium is a secondary messenger in plant stress signaling, and the treatment of calcium has been proposed to alleviate damage by various abiotic stresses. The objective of this research was to evaluate application methods of calcium to delay plant wilting under water deficiency in three species of bedding plants: viola (Viola cornuta), impatiens (Impatiens walleriana), and petunia (Petunia grandiflora). Three application methods were compared including spray, drench, and pre-drench. Calcium was applied as CaCl2 and Ca(NO3)2 at three concentrations ranging from 50 to 300 mM. The effect of calcium on shelf life was species-dependent, increasing shelf life in viola and impatiens, but not in petunia. Viola showed increased shelf life up to 154% and 400% in drench and pre-drench applications, respectively, compared to the control. In impatiens, spray and pre-drench applications delayed wilting symptoms by 53% and 200%, respectively. Comparing calcium sources, CaCl2 was the most effective as a drench, while Ca(NO3)2 pre-drench application effectively delayed wilting. There was no difference between CaCl2 and Ca(NO3)2 in spray application. These results provided the optimum application methods to delay plant witling and the potential of calcium application on enhancing water deficit tolerance in floriculture crops.

Chitosan and salicylic acid regulate morpho-physiological and phytochemical parameters and improve water-deficit tolerance in milk thistle (Silybum marianum L.)

Chitosan and salicylic acid regulate morpho-physiological and phytochemical parameters and improve water-deficit tolerance in milk thistle (Silybum marianum L.)

Ectopic expression of GmNHX3 and GmNHX1, encoding two Glycine max Na<sup>+</sup>/H<sup>+</sup> vacuolar antiporters, improves water deficit tolerance in Arabidopsis thaliana

The importance of Na+/H+ antiporters in salt tolerance in plants has been demonstrated in many studies, but much less is known about their protective role during drought stress. To study their possible contribution to water deficit tolerance, two closely related soybean Na+/H+ antiporters belonging to the intracellular NHX exchanger protein family, GmNHX3 and GmNHX1, were evaluated in transgenic Arabidopsis thaliana. A. thaliana plants ectopically expressing GmNHX3 or GmNHX1 displayed a more drought-tolerant phenotype compared to wild-type plants, which was accompanied by an increase in relative water content and chlorophyll content during stress conditions. Both GmHNX1 and GmHNX3 transgenic lines accumulated higher amounts of Na+ and K+ cations, showed increased antioxidant enzyme activities and less membrane damage due to lipid peroxidation under water deficit, as compared to non-transformed plants. Furthermore, plants expressing GmNHX3 showed an increased sensitivity to abscisic acid as deduced from stomatal closure and seed germination inhibition studies. Finally, a significant up-regulation of abiotic stress-related genes was observed in both transgenic lines compared to wild-type plants in response to abscisic acid and mannitol treatments. These results demonstrate that GmNHX3 and GmNHX1 antiporters confer protection during drought stress in A. thaliana and hence are potential genetic targets to improve drought tolerance in soybean and other crops.

Different strategies lead to a common outcome: different water-deficit scenarios highlight physiological and biochemical strategies of water-deficit tolerance in diploid versus tetraploid Volkamer lemon.

Water scarcity restricts citrus growth and productivity worldwide. In pot conditions, tetraploid plants tolerate water deficit more than their corresponding diploids. However, their tolerance mechanisms remain elusive. In this study, we focused on which mechanisms (i.e., hydraulic, osmotic or antioxidative) confer water-deficit tolerance to tetraploids. We exposed diploid and tetraploid Volkamer lemon rootstock (Citrus volkameriana Tan. and Pasq.) to quickly (fast) and slowly (slow) developing water-deficit conditions. We evaluated their physiological, antioxidative defense and osmotic adjustment responses, and mineral distribution to leaves and roots. Water-deficit conditions decreased the photosynthetic variables of both diploid and tetraploid plants. Moreover, the corresponding decrease was greater in diploids than tetraploids. Higher concentrations of antioxidant enzymes, osmoprotectants and antioxidant capacity were found in the leaves and roots of tetraploids than diploids under water deficit. Diploid plants showed fast response in slow water-deficit condition, but that response did not persist as the deficit intensified. Meanwhile, tetraploids had lower water loss, which slowed the onset of slow water deficit relative to diploids. This response allowed stronger photosynthesis, while antioxidant and osmoprotectant production allowed for further tolerance once desiccation began. Overall, our results concluded that Volkamer lemon tetraploid plants tolerate rapid and slow water deficit by maintaining their photosynthesis due to low conductance (stem or roots), which helps to avoid desiccation, and stronger biochemical defense machinery than their corresponding diploids.

Overexpression of the CaHB12 transcription factor in cotton (Gossypium hirsutum) improves drought tolerance

The Coffea arabica HB12 gene (CaHB12), which encodes a transcription factor belonging to the HD-Zip I subfamily, is upregulated under drought, and its constitutive overexpression (35S:CaHB12OX) improves the Arabidopsis thaliana tolerance to drought and salinity stresses. Herein, we generated transgenic cotton events constitutively overexpressing the CaHB12 gene, characterized these events based on their increased tolerance to water deficit, and exploited the gene expression level from the CaHB12 network. The segregating events Ev8.29.1, Ev8.90.1, and Ev23.36.1 showed higher photosynthetic yield and higher water use efficiency under severe water deficit and permanent wilting point conditions compared to wild-type plants. Under well-irrigated conditions, these three promising transformed events showed an equivalent level of Abscisic acid (ABA) and decreased Indole-3-acetic acid (IAA) accumulation, and a higher putrescine/(spermidine + spermine) ratio in leaf tissues was found in the progenies of at least two transgenic cotton events compared to non-transgenic plants. In addition, genes that are considered as modulated in the A. thaliana 35S:CaHB12OX line were also shown to be modulated in several transgenic cotton events maintained under field capacity conditions. The upregulation of GhPP2C and GhSnRK2 in transgenic cotton events maintained under permanent wilting point conditions suggested that CaHB12 might act enhancing the ABA-dependent pathway. All these data confirmed that CaHB12 overexpression improved the tolerance to water deficit, and the transcriptional modulation of genes related to the ABA signaling pathway or downstream genes might enhance the defense responses to drought. The observed decrease in IAA levels indicates that CaHB12 overexpression can prevent leaf abscission in plants under or after stress. Thus, our findings provide new insights on CaHB12 gene and identify several promising cotton events for conducting field trials on water deficit tolerance and agronomic performance.

Physiological and biochemical responses of Kinnow mandarin grafted on diploid and tetraploid Volkamer lemon rootstocks under different water-deficit regimes.

Water shortage is among the major abiotic stresses that restrict growth and productivity of citrus. The existing literature indicates that tetraploid rootstocks had better water-deficit tolerance than corresponding diploids. However, the associated tolerance mechanisms such as antioxidant defence and nutrient uptake are less explored. Therefore, we evaluated physiological and biochemical responses (antioxidant defence, osmotic adjustments and nutrient uptake) of diploid (2x) and tetraploid (4x) volkamer lemon (VM) rootstocks grafted with kinnow mandarin (KM) under two water-deficit regimes. The KM/4xVM (VM4) and KM/2xVM (VM2) observed decrease in photosynthetic variables, i.e., photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (E), leaf greenness (SPAD), dark adopted chlorophyll fluorescence (Fv/Fm), dark adopted chlorophyll fluorescence (Fv´/Fm´), relative water contents (RWC) and leaf surface area (LSA), and increase in non-photochemical quenching (NPQ) under both water-deficit regimes. Moreover, oxidative stress indicators, i.e., malondialdehyde (MDA) and hydrogen peroxide, and activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APx), glutathione reductase (GR) were increased under both water-deficit regimes. Nonetheless, increase was noted in osmoprotectants such as proline (PRO) and glycine betaine (GB) and other biochemical compounds, including antioxidant capacity (AC), total phenolic content (TPC) and total soluble protein (TSP) in VM2 and VM4 under both water-deficit regimes. Dry biomass (DB) of both rootstocks was decreased under each water-deficit condition. Interestingly, VM4 showed higher and significant increase in antioxidant enzymes, osmoprotectants and other biochemical compounds, while VM2 exhibited higher values for oxidative stress indicators. Overall, results indicated that VM4 better tolerated water-deficit stress by maintaining photosynthetic variables associated with strong antioxidant defence machinery as compared to VM2. However, nutrient uptake was not differed among tested water-deficit conditions and rootstocks. The results conclude that VM4 can better tolerate water-deficit than VM2. Therefore, VM4 can be used as rootstock in areas of high-water deficiency for better citrus productivity.

Evaluation of Water Deficit Tolerance Indices in New Hybrids of Maize (Zea mays L.) with SIMMYT Origin

Evaluation of Water Deficit Tolerance Indices in New Hybrids of Maize (Zea mays L.) with SIMMYT Origin

Physiological, Biochemical and Yield-Component Responses of Solanum tuberosum L. Group Phureja Genotypes to a Water Deficit.

Water deficits are the major constraint in some potato-growing areas of the world. The effect is most severe at the tuberization stage, resulting in lower yield. Therefore, an assessment of genetic and phenotypic variations resulting from water deficits in Colombia germplasm is required to accelerate breeding efforts. Phenotypic variations in response to a water deficit were studied in a collection of Solanum tuberosum Group Phureja. A progressive water deficit experiment on the tuberization stage was undertaken using 104 genotypes belonging to the Working Collection of the Potato Breeding Program at the Universidad Nacional de Colombia. The response to water deficit conditions was assessed with the relative chlorophyll content (CC), maximum quantum efficiency of PSII (Fv/Fm), relative water content (RWC), leaf sugar content, tuber number per plant (TN) and tuber fresh weight per plant (TW). Principal Component Analysis (PCA) and cluster analysis were used, and the Drought Tolerance Index (DTI) was calculated for the variables and genotypes. The soluble sugar contents increased significantly under the deficit conditions in the leaves, with a weak correlation with yield under both water treatments. The PCA results revealed that the physiological, biochemical and yield-component variables had broad variation, while the yield-component variables more powerfully distinguished between the tolerant and susceptible genotypes than the physiological and biochemical variables. The PCA and cluster analysis based on the DTI revealed different levels of water deficit tolerance for the 104 genotypes. These results provide a foundation for future research directed at understanding the molecular mechanisms underlying potato tolerance to water deficits.

PdGNC confers drought tolerance by mediating stomatal closure resulting from NO and H2 O2 production via the direct regulation of PdHXK1 expression in Populus.

Drought is one of the primary abiotic stresses, seriously implicating plant growth and productivity. Stomata play a crucial role in regulating drought tolerance. However, the molecular mechanism on stomatal movement-mediated drought tolerance remains unclear. Using genetic, molecular and biochemical techniques, we identified that the PdGNC directly activating the promoter of PdHXK1 by binding the GATC element, a hexokinase (HXK) synthesis key gene. Here, PdGNC, a member of the GATA transcription factor family, was greatly induced by abscisic acid and dehydration. Overexpressing PdGNC in poplar (Populus clone 717) resulted in reduced stomatal aperture with greater water-use efficiency and increased water deficit tolerance. By contrast, CRISPR/Cas9-mediated poplar mutant gnc exhibited increased stomatal aperture and water loss with reducing drought resistance. PdGNC activates PdHXK1 (a hexokinase synthesis key gene), resulting in a remarkable increase in hexokinase activity in poplars subjected to water deficit. Furthermore, hexokinase promoted nitric oxide (NO) and hydrogen peroxide (H2 O2 ) production in guard cells, which ultimately reduced stomatal aperture and increased drought resistance. Together, PdGNC confers drought stress tolerance by reducing stomatal aperture caused by NO and H2 O2 production via the direct regulation of PdHXK1 expression in poplars.

Exogenous application of paclobutrazol promotes water-deficit tolerance in pepper (Capsicum annuum)

Abstract. Slichatun, Khasanah FU, Pitoyo A, Etikawati N, Mudyantini W. 2021. Exogenous application of paclobutrazol promotes water-deficit tolerance in pepper (Capsicum annuum). Cell Biol Dev 5: 1-6. Pepper (Capsicum annuum L.) is a vegetable commodity with high economic value. However, pepper cultivation in Indonesia is still hampered by pests and drought, reducing its growth and production. The efforts to increase pepper productivity and its resistance to drought stress can be conducted by applying growth regulators (ZPT), one of which is paclobutrazol (PBZ). This study aims to determine the effect of PBZ on the growth and accumulation of proline, a plant osmoprotectant, in pepper seedlings grown in water-deficit soil. This study used a completely randomized design (CRD) with two factors, i.e., a variation of PBZ and soil water capacity. PBZ concentration was made in four levels, namely 0 ppm, 25 ppm, and 50 ppm. The variation of the water-capacity level was made in three levels, namely 100% FC (field capacity as well-watered treatment), 75% FC (mild water deficit), and 50% FC (severe water deficit). The treatment was given for three weeks. The quantitative data obtained were analyzed by ANOVA, and if there was a significant difference, a further test was carried out with DMRT at the 95% confidence level. In addition, qualitative data were analyzed descriptively. The results showed that applying PBZ to pepper (Capsicum annuum L.) seedlings that grew under water-deficit stress significantly affected proline levels, total chlorophyll content, and carotenoid levels; meanwhile, the parameters of plant dry weight and root shoot ratio had no significant effect. Furthermore, this indicates that PBZ is quite capable of inducing resistance to pepper seedlings in drought conditions.

Silicon-Mediated Priming Induces Acclimation to Mild Water-Deficit Stress by Altering Physio-Biochemical Attributes in Wheat Plants.

Water-deficit stress negatively affects seed germination, seedling development, and plant growth by disrupting cellular and metabolic functions, reducing the productivity and yield of field crops. In this study, sodium silicate (SS) has been employed as a seed priming agent for acclimation to mild water-deficit stress by invoking priming memory in wheat plants. In pot experiments, the SS-primed (20, 40, and 60 mM) and non-primed control seeds were allowed to grow under normal and mild water-deficit conditions. Subsequently, known methods were followed for physiological and biochemical studies using flag leaves of 98-day mature wheat plants. The antioxidant and hydrolytic enzymes were upregulated, while proteins, reducing sugars, total sugars, and glycine betaine increased significantly in the flag leaves of wheat plants originated from SS-treated seeds compared to the control under mild water-deficit stress. Significant decreases in the malondialdehyde (MDA) and proline contents suggested a controlled production of reactive oxygen species, which resulted in enhanced cell membrane stability. The SS priming induced a significant enhancement in yield, plant biomass, and 100-grain weight of wheat plants under water-deficit stress. The improvement in the yield parameters indicated the induction of Si-mediated stress acclimation in SS-primed seeds that elicited water-deficit tolerance until the maturity of plants, ensuring sustainable productivity of climate-smart plants.

Elevated Nitrogen Priming Induced Oxinitro-Responses and Water Deficit Tolerance in Rice.

Under water deficit conditions, the essential macronutrient nitrogen becomes limited as a result of reduced dissolved nitrogen and root nitrogen uptake. An elevated nitrogen level might be able to mitigate these effects, integrated with the idea of using nitric oxide as abiotic stress tolerant inducers. In this study, we evaluated the potential of using elevated nitrogen priming prior to water shortage to mitigate plant stress through nitric oxide accumulation. We grew rice plants in 300 mg L−1 nitrogen for 10 weeks, then we primed plants with four different nitrogen concentrations: 100, 300 (control), 500 and 1000 mg L−1 nitrogen prior to inducing water deficit conditions. Plants primed with 500 mg L−1 nitrogen possessed a higher photosynthetic rate, relative water content, electrolyte leakage and lipid peroxidation under water deficit conditions, compared to control plants. The induction of water deficit tolerance was supported with the activation of antioxidant defense system, induced by the accumulation of nitric oxide in leaves and roots of rice plants. We originally demonstrated the accumulation of nitric oxide in leaves of rice plants. The elevated nitrogen priming can be used to enhance water deficit tolerance in irrigated paddy fields, instead of nitric oxide donors.

Sodium nitroprusside mediated priming memory invokes water-deficit stress acclimation in wheat plants through physio-biochemical alterations

AimWater-deficit stress is the most devastating environmental factor that adversely affects plant growth causing yield losses and low crop productivity. In this study, we employed sodium nitroprusside (SNP) as a seed priming agent for the acclimation of water-deficit stress in wheat plants by invoking priming memory. MethodsThe SNP-primed (75, 100, and 125 μM) and non-primed controls were allowed to grow in pots under water deficit and normal conditions. The flag leaves of 98-days mature plants were used for biochemical and physiological studies by following the well-established methods. ResultsThe antioxidant and hydrolytic enzymes were upregulated while reducing sugars, total sugars, and glycine betaine increased significantly in flag leaves of wheat plants originated from SNP-treated seeds compared to control under water deficit stress. However, a significant reduction in MDA and proline contents represented a lesser ROS production which resulted in enhanced cell membrane stability. Consequently, there was a significant enhancement in yield, plant biomass and 100 grains weight of wheat plants under water deficit stress. ConclusionThe improvement in yield parameters indicates the induction of priming memory in SNP-primed seeds which elicit water deficit tolerance till the maturity of plants thus ensures sustainable productivity of wheat.

Physiological traits coupled with water deficit tolerance by using multivariate analysis in cotton genotypes.

The water shortage is a serious hazard for food security in the world. It is the alarming situation for the plant breeders to recognize and build up drought tolerant field crops germplasm. The water deficit tolerance magnitude rely on various soil and plant associated factors such as capacity of soil to accumulate moisture, rainfall distribution, rate of evapo-transpiration and root uniqueness. The present study was done at Central Cotton Research Institute, Multan to screen cotton germplasm against water deficit by irrigating the plants at three moisture levels at seedling stage i.e., 40, 70, and 100% of the pot capacity. The data on root length, fresh root weight, shoot length, fresh shoot weight, dry root weight, dry shoot weight and ratio of root and shoot were collected of 45 days plants after exposing to water deficit. Mean values of seedling parameters revealed differences for water deficit tolerance. Cluster analysis was performed by using Ward's method (1963). Five clusters (I, II, III, IV and V) comprised of various genotypes of cotton were observed at three moisture levels. Cluster I showed the genotypes having almost maximum values of root shoot parameters while cluster V with minimum values at all the moisture levels. These results showed the presence of drought tolerance genotypes in cluster I and susceptible genotypes in cluster V. In Biplot analysis, variables and genotypes are super imposed on the plot as vectors. The genetic variation in genotypes in different cluster showed the existence of water deficit tolerance which could be applied for the evolution of drought tolerant genotypes.

Effect of Drought on Various Agro-physical Parameters of Chickpea (<i>Cicer arietinum</i> L.) Genotypes in a Field Experiment

Drought stress is one of the major factors limiting the growth and development of legumes. In order to improve water deficit tolerance of this crop, several techniques have been put into practice such as seed priming or the selection of tolerant genotypes to water stress. In 2020, field experiment was conducted to assess the drought tolerance of thirty-six chickpea genotypes (<i>C. arietinum</i>) by analyzing the behaviour of certain physiological and biochemical parameters of plants harvested in a randomized field experiment. The genotypes analysed presented a diversity of behavior concerning the accumulation of mineral elements under drought. The results showed an accumulation of inorganic ions, especially calcium and potassium (1.8 and 2 mg.g^-1, respectively) and increased proline and protein content (3.4 and 1.7 mg.g^-1, respectively) has been observed in drought tolerant chickpea genotypes. Also, the results obtained showed that the P contents in the aerial parts are generally higher for plants with a high biomass, such as the case of genotypes V36 and V32. This tends to prove the positive effect of P on plant growth. After analysis of the various parameters, the results obtained allowed us to classify the tolerant genotypes:, V36, V38 andV41, intermediates: V40 and V4 and sensitive: V17 and V28.