Greater Accumulation Of Proline Research Articles

Co-Expression of JcNAC1- and JcZFP8-Improved Agronomic Traits of Tobacco and Enhanced Drought Resistance through NbbHLH1 and NbbHLH2.

Previous studies have identified numerous transcription factors involved in drought response, each of which play different roles in plants. The objective of the present study was to evaluate the effectiveness of two transcription factors on drought response in Jatropha curcas L., JcNAC1 and JcZFP8. The overexpression of these transcription factors in tobacco (Nicotiana benthamiana L.) improved drought resistance, but JcZFP8 delayed germination and JcNAC1 reduced biomass and yield. By constitutively co-expressing these two genes in tobacco, drought resistance was improved, and the negative effects of each of them were overcome. The transgenic plants with double-gene co-expression showed stronger drought tolerance with 1.76-fold greater accumulation of proline and lower H2O2 and malondialdehyde (MDA) content to 43 and 65% of wildtype (WT) levels, respectively. The expression levels of NbbHLH1 and NbbHLH2 genes upregulated linearly with the increased drought tolerance of double genes co-expression plants. In drought conditions, the leaf water contents of bhlh1, bhlh2, and bhlh1bhlh2 deletion mutants obtained by CRISPR-CAS9 knockout technique were maintained at 99%, 97%, and 97% of WT. The bhlh1bhlh2 was found with lower germination rate but with higher reactive oxygen levels (1.64-fold H2O2 and 1.41-fold MDA levels). Thus, the co-expression of two transcription factors with different functions overcame the adverse traits brought by a single gene and enhanced the shared drought-tolerant traits, which can provide guidance on theory and selection of gene combinations for the application of multi-gene co-expression in agriculture in the future.

Genotype- and tissue-specific physiological and biochemical changes of two chickpea (Cicer arietinum) varieties following a rapid dehydration.

In nature, plants may suffer rapid dehydration (RD), which causes significant loss of the annual global chickpea production. Thus, ascertaining more knowledge concerning the RD-tolerance mechanisms in chickpea is crucial for developing high drought-tolerant varieties to assure sustainable chickpea production under sudden water deficit. Here, we focused on genotype-driven variation in leaf relative water content (RWC) and associated differences in RD-responsive physiological and biochemical attributes in roots and leaves of two chickpea varieties, FLIP00-21C and FLIP02-89C, subjected to well-watered and RD conditions. FLIP00-21C showed higher RD-tolerance than FLIP02-89C, evident by its higher leaf RWC during RD. Consistently, FLIP00-21C exhibited lower membrane injury due to lower hydrogen peroxide (H2 O2 ) accumulation than FLIP02-89C during RD, indicating reduced RD-induced oxidative damage. Under RD conditions, total phenolics in roots and flavonoids in roots and leaves increased more in FLIP02-89C compared to FLIP00-21C; however, the increased activities of superoxide dismutase and H2 O2 -scavenging enzymes were more properly coordinated in FLIP00-21C than in FLIP02-89C, which might contribute to more efficient antioxidant defense in FLIP00-21C than in FLIP02-89C. The higher leaf RWC of FLIP00-21C versus FLIP02-89C under RD might be associated with greater increases in the levels of the osmo-regulators proline and total free amino acids (TFAAs) in FLIP00-21C than in FLIP02-89C. Collectively, the higher RD-tolerance of FLIP00-21C is mainly associated with the maintenance of higher RWC, stronger antioxidant defense, and greater accumulation of proline and TFAAs. These traits could be useful for evaluating the drought-tolerance of chickpea varieties and further marker-assisted breeding approaches for improvement of chickpea productivity.

Proteomic responses to progressive dehydration stress in leaves of chickpea seedlings

BackgroundChickpea is an important food legume crop with high protein levels that is widely grown in rainfed areas prone to drought stress. Using an integrated approach, we describe the relative changes in some physiological parameters and the proteome of a drought-tolerant (MCC537, T) and drought-sensitive (MCC806, S) chickpea genotype.ResultsUnder progressive dehydration stress, the T genotype relied on a higher relative leaf water content after 3 and 5 d (69.7 and 49.3%) than the S genotype (59.7 and 40.3%) to maintain photosynthetic activities and improve endurance under stress. This may have been facilitated by greater proline accumulation in the T genotype than the S genotype (14.3 and 11.1 μmol g− 1 FW at 5 d, respectively). Moreover, the T genotype had less electrolyte leakage and lower malondialdehyde contents than the S genotype under dehydration stress, indicating greater membrane stability and thus greater dehydration tolerance. The proteomic analysis further confirmed that, in response to dehydration, the T genotype activated more proteins related to photosynthesis, stress response, protein synthesis and degradation, and gene transcription and signaling than the S genotype. Of the time-point dependent proteins, the largest difference in protein abundance occurred at 5 d, with 29 spots increasing in the T genotype and 30 spots decreasing in the S genotype. Some of the identified proteins—including RuBisCo, ATP synthase, carbonic anhydrase, psbP domain-containing protein, L-ascorbate peroxidase, 6-phosphogluconate dehydrogenase, elongation factor Tu, zinc metalloprotease FTSH 2, ribonucleoproteins and auxin-binding protein—may play a functional role in drought tolerance in chickpea.ConclusionsThis study highlights the significance of genotype- and time-specific proteins associated with dehydration stress and identifies potential resources for molecular drought tolerance improvement in chickpea.

Drought-induced stress in leaves of Coix lacryma-jobi L. under exogenous application of proline and GABA amino acids

Coix lacryma-jobi L. is an Asian plant widely used in traditional medicine. Drought conditions can lead to an impairment of photosynthesis which can be softened by the exogenous application of proline and γ-aminobutyric acid (GABA) to maintain the electron transport chain (ETC) and avoid reactive oxygen species-induced oxidative damage by inducing antioxidative enzymes. The aim of this study was to evaluate the effects of water deficit on C. lacryma-jobi leaves under the application of proline and GABA. Chlorophyll (Chl) a fluorescence emission, antioxidative enzyme activity (catalase, superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase) and proline and GABA contents in leaf tissues were performed in plants subjected to 12 days of drought. Chl a fluorescence indicated impairments on photosynthetic apparatus due to water deficit that resulted into increased activity of antioxidant enzymes. The application of proline but not GABA was more efficient in alleviating the effects of water deficit, as evidenced by the maintenance of the dynamic dissipation of the photosynthetic energy, besides the greater accumulation of proline under these conditions. Water deficit induces alterations in the ETC, which is softened by the application of proline to cope with the deleterious effects of drought in C. lacryma-jobi plant leaves.

Ectopic overexpression of cytosolic ascorbate peroxidase gene (Apx1) improves salinity stress tolerance in Brassica juncea by strengthening antioxidative defense mechanism

Salinity stress is considered to be a key constrain that reduces the crop productivity by impairing plant growth and development. During salt stress condition, an underlying mechanism for reduction in crop yield is increase in ROS level that can potentially harm cellular macromolecules, leading to disruption of essential physiological and biochemical processes. Plants possess a complex antioxidative defense machinery for scavenging these ROS. Ascorbate peroxidase (APX, E.C. 1.11.1.11), is a crucial antioxidant enzyme involved in Ascorbate–Glutathione pathway that primarily detoxifies the negative impact of H2O2 in cell. The efficient scavenging of H2O2 is a prerequisite for enhanced tolerance to salinity stress. Here, we have inspected whether over-expression of APX could provide protection against salinity stress. Cytosolic ascorbate peroxidase (Apx1) gene, isolated from Arabidopsis thaliana, was chosen as the candidate gene for strengthening the antioxidative defense system of Brassica juncea. Physiological parameters were employed to analyze the growth status of transgenic plants. Leaf disc assay was done to evaluate the salinity stress tolerance potential of transgenic plants, using several physiological and biochemical parameters. Under salinity stress, the transgenic plants performed well as compared to their non-transgenic counterparts; as revealed through greater proline accumulation, increased chlorophyll stability index, lower chlorophyll a/b ratio, and higher antioxidative enzyme activities. Further, the lower H2O2 levels were well correlated with lesser membrane damage as measured through MDA content. Collectively, our results clearly depicted that ectopic overexpression of AtApx1 gene was able to confer salinity stress tolerance by strengthening the antioxidative defense system in B. juncea.

Seedling, early vegetative, and adult plant growth of oilseed rapes (Brassica napus L.) under saline stress

Salinity is a major limiting factor for early crop establishment and yield. In this study, 131 Brassica napus genotypes were evaluated for germination and early seedling growth in Murashige & Skoog medium supplemented with NaCl. Selected genotypes were then evaluated for tolerance to salinity at the vegetative and reproductive stages in greenhouse and semi-hydroponic systems using 1.4, 5, 10, 15, 20, and 28 dS m−1 salt stress. Relative salt tolerance (RST) was calculated and compared with genotype performance under no salt stress (control). The area under the germination progress curve (AUGPC) varied from 53 to 90 in the control and from 6 to 89 under 200 mmol L−1 NaCl stress. The seedling vigor index (SVI) ranged from 200 to 1606 and 10 to 736 in the control and 200 mmol L−1 salt stress treatments, respectively. The RST for germination, root length, shoot length, and SVI ranged from 8% to 97.7%, 2% to 98.3%, 6.5% to 70.8%, and 1.9% to 83%, respectively. Root length was most severely affected by saline conditions, followed by shoot length and AUGPC, when RST percentages of these traits were compared among responses of the 131 genotypes. Genotypes showed varying levels of proline and glucosinolate accumulation under different levels of saline stress. Greater accumulation of proline and glucosinolates was recorded with increased salinity level. This study indicates that variation exists in seedling and adult plant responses to saline stress in B. napus genotypes and that improvement for salinity tolerance requires selection at the seedling, vegetative, and reproductive plant stages.

Traditional Varieties of Caupi Submitted to Water Deficit: Physiological and Biochemical Aspects

The cowpea (Vigna unguiculata (L.) Walp) it is a leguminous widely cultivated in Northeast of Brazil. In the state of Ceara, its cultivation is performed mainly by family farms who make use of traditional varieties of good adaptation to the growing region. Thus, characterizing traditional varieties with characteristics of adaptation to regions with water shortage is essential for the production of food in the world, especially in semi-arid regions. In this sense, the objective was to evaluate the physiological and biochemical responses in three genotypes of cowpea, being two traditional varieties grown in Ceara (Sempre-Verde and Cabeça-de-Gato) and a genotype characterized as a standard of drought tolerance (Pingo-de-Ouro-1,2) under three water regimes: irrigated, moderate deficit and severe water deficit. The parameters evaluated were: gas exchange, chlorophyll a fluorescence, photosynthetic pigments, organic solutes (proline, total carbohydrates, reducing and non-reducing carbohydrates), starch and enzyme activity (APX, G-POD, CAT and SOD). The genotype Pingo-de-Ouro-1,2 confirmed its tolerance pattern in a water deficit condition, presenting greater water potential, higher photosynthetic rate, high levels of total carbohydrates and high accumulation of proline. Among the traditional varieties, the Cabeça-de-Gato presented superior photosynthesis to Sempre-Verde higher Electron Transport Rate (ETR), reflecting in a greater photochemical quenching (qP) and a greater accumulation of proline, indicating that this variety presents more pronounced adaptive characteristics for water restriction conditions, which is a common condition to the Brazilian semiarid.

Adaptation of sugarcane plants to saline soil

Sugarcane is an important crop in tropical regions of the world, often being exposed to environments with high salinity, but little is known of genetic variation in salt tolerance. The aim of this work was to compare the performance of two genetically diverse cultivars of sugarcane under different concentrations of salinity (0, 40, 80 and 160 mM NaCl) over a period of 30 days. SP 81–3250 was more salt-tolerant and maintained its rate of biomass production, photosynthesis and leaf area up to 160 mM NaCl, whereas IAC 87–3396 was sensitive to 80 mM NaCl. SP 81–3250 maintained very low concentrations of Na+ in both leaves and roots with increasing time and salinity, whereas in IAC 87–3396 the Na+ concentrations were 2–5 times higher. SP 81–3250 ha d a greater accumulation of proline, and lower lipid peroxidation, whereas glycine betaine and sucrose concentrations were similar in the two cultivars. This suggests that the tolerance of SP 81–3250 to high salinity was due to its ability to exclude Na+ while taking up water from the soil, and that measurements of Na+ concentration in leaves could be used to select salt-tolerant genotypes for saline areas.

Afectaciones fisiológicas y bioquímicas en vitroplantas de caña de azúcar en respuesta al estrés hídrico y salino

La producción agrícola es afectada negativamente por estrés biótico y abiótico, siendo responsables de grandes pérdidas económicas en el mundo. La caña de azúcar es la materia prima para obtener jugo de caña que se transforma en sacarosa y en la producción de etanol de segunda generación. En el presente estudio se evaluó el número de brotes y hojas, la concentración de prolina, clorofila a, b y total y la concentración de azúcares como respuesta al estrés hídrico y salino en dos variedades de caña de azúcar in vitro. Brotes individualizados de 5 cm de longitud de las variedades MotzMex 91-207 y SP 71-6180 de caña de azúcar se cultivaron in vitro bajo estrés hídrico (PEG 6000) y salino (NaCl). Las dos variedades de caña de azúcar analizadas in vitro presentaron respuestas diferentes al estrés osmótico. La variedad MotzMex 91-207 fue mejor que la variedad SP 71-6180 para responder al estrés hídrico con una mayor acumulación de prolina (82.34 mg g-1 PS), no presentó disminución en el contenido de clorofilas a, b y total y generó 20.8 brotes por explante aun en condiciones de estrés. Por otro lado, la respuesta al estrés salino con 50 mM NaCl in vitro la presentó la variedad SP 71-6180 al generar una mayor acumulación de carbohidratos como galactosa, glucosa y manosa.

Phytotoxic effects of trivalent chromium-enriched water irrigation in Vigna unguiculata seedling

The present study attempts to investigate the degree of inhibition of trivalent chromium on the seed germination and embryonic axis growth of Vigna unguiculata seedlings. The alteration of chloroplastic pigments, and the unique roles of different enzymatic and non-enzymatic antioxidants against chromium-induced stress were elucidated. Chromium treatment has adversely retarded the elongation of roots and shoots, with the inhibition rate of 68.5% and 70%, respectively. The chlorophyll-a, chlorophyll-b, and carotenoid contents were significantly altered, denoted the reduction of 60.3%, 67.2%, and 43.7%, respectively. Higher stimulation effects have been observed in the ascorbate peroxidase, catalase, and guaiacol peroxidase at different degrees, and a greater accumulation of proline was detected. The current findings provided an up-to-date picture on the phytotoxicity of chromium ions on the physical, chemical, and physiological alterations of Vigna unguiculata seedlings, and triggered the cellular enzymatic and non-enzymatic antioxidants against these oxidative injuries. The health threats associated with the excessive accumulation of anthropogenic pollutants in the food crops could be exacerbated on a wider scale by unregulated wastewater irrigation practice, and place an alarming deterioration to the sustainability of water-food nexus.

Physiological Traits and Yield Performance of Mungbean (Vigna radiata (L) Wilczek) as Influenced by Light Intensities

An experiment was carried out at the Crop Physiology and Ecology Research Field, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur during the period from March to June 2016 to evaluate some physiological traits and yield performance of mungbean variety under different light intensities and to find out potential mungbean variety as intercrop. The experiment was laid out in a split -plot design with three replications. Three light intensities (L100 - full sunlight, L75- 75 % of full sunlight and L50- 50% of full sunlight) were assigned in the main plots and four varieties (BARl Mung-6, Binamoong8, Binamoong5 and BU Mug-4) in the subplots. White and red colour Mosquito nets were used for maintaining 75 and 50 percent of full sunlight. Light percentages of mosquito nets were measured by light meter (21YE35). Mosquito nets of different colors and pore size were used for maintaining 75 and 50 percent of full sunlight. The seed yield of BARI Mung-6 and Binamoong8 performing well in under partial shade condition but the grain yield of Binamoong5 and BU Mug-4 was reduced drastically under partial shade condition. Greater proline accumulation in leaf, higher leaf chlorophyll content, higher pods plant-1, higher seeds pod-1, greater seed size and better seed yield plant-1 under partial shade condition were contributed to better tolerance of BARI Mung-6 and Binamoong8 under low light stress.Bangladesh Agron. J. 2017, 20(2): 67-74

Analysis of metabolic and nutritional biomarkers in Brassica oleracea L. cv. Bronco plants under alkaline stress

ABSTRACTAlkaline stress is caused by accumulation of alkaline salts (such as NaHCO3 and Na2CO3) in the soil. This problem, common in arid and semiarid areas of Spain, results from intensive agriculture, the use of hard water, and cultivation in areas of calcareous rock. The present study examines plant metabolic responses against this stress in Brassica oleracea L. cv. Bronco in order to better understand the systems of resistance that could promote plant growth in alkaline soils, and indicates the most relevant biomarkers of alkalinity toxicity. Alkaline stress causes a sharp reduction in biomass, an accumulation of Na+, and a nutritional deficiency. With this debilitated photosynthetic capacity and the antioxidant activity, superoxide dismutase (SOD) sharply decreases and O2.- accumulates, resulting in two of the main causes of stress. Therefore the mechanisms of uptake and compartmentalisation of nutrients and detoxification of O2.- systems should be strengthened in order to remedy alkaline stress. In this work, the authors conclude that Na, P, K, Ca, Mg, and Mn ions are the best indicators of alkaline stress, due to their strong correlation with reduced leaf biomass reduction and photosynthetic pigments, together with the greater accumulation of proline and certain antioxidant enzymes such as SOD.

Proline accumulation in sugarcane roots subjected to drought conditions

Sugarcane cultivation faces various environmental stresses, among which drought is one of the most aggra­vating to production. As a result of this, we know that proline accumulation in cells is one of the factors respon­sible for drought-tolerance in plants. Thus, this paper aimed to evaluate accumulations in proline levels in the roots of two sugarcane cultivars subjected to drought, one of them tolerant (RB867515) and the other sensitive (SP86-155). The experiment was conducted in a greenhouse and the plants were subjected to 1, 3, 5, and 10 days of water deficit. The free proline level in tolerant sugarcane roots was statistically significant after 10 days of irrigation suppression, with an expressive difference of 25.43%, when compared to the sensitive plant. The greater accumulation of proline in the tolerant cultivar proved its drought-tolerant character; this osmoprotectant helped the plants to maintain their turgor after 5 days of water deficit (moderate stress) and to cope with a greater water deficit for 10 days (severe stress), when compared with the sensitive plant. The result from this paper indicates that the metabolism of proline accelerated the cell signaling processes which promoted cell and tissue turgidity, favoring the survival of the tolerant cultivar for a greater period of water deficit.

Screening of Eight Eucalypt Genotypes (Eucalyptus sp.) for Water Deficit Tolerance Using Multivariate Cluster Analysis

The present study evaluated eight genotypes of river red gum (Eucalyptus camaldulensis Dehnh.) and a hybrid (E. camaldulensis × E. urophylla) for mannitol-induced water deficit (WD) under photoautotrophic conditions using multivariate cluster analysis. Shoot height, plant dry weight, and chlorophyll a content in hybrid genotypes, 58H2 and 27A2, were maintained when exposed to 200mM mannitol for 14days. In addition, the diminution of photosynthetic abilities, i.e. maximum quantum yield of PSII, photon yield of PSII, photochemical quenching, and net photosynthetic rate, under WD was minimal in hybrid genotypes compared to that in selection clones of E. camaldulensis. Under WD condition, there was greater accumulation of proline in all genotypes. A positive relationship was observed between physiological and morphological attributes under WD stress. Using Ward's cluster analysis, hybrid genotypes-H4, 58H2, and 27A2-were classified as water deficit tolerant.

Assessment of genetic diversity and morpho-physiological traits related to drought tolerance in Stylosanthes scabra

Among the many Stylosanthes species, Stylosanthes scabra, a range fodder legume, performs better under limited water condition. In the present investigation, thirty-four accessions of S. scabra were assessed under limited water condition, for various morpho-physiological characters associated with drought. In general, S. scabra exhibited better tolerance to drought, as evidenced by high leaf thickness and greater accumulation of proline, and malondialdehyde (MDA) in water stress condition. Transpiration efficiency (TE) was high, in both control and water stress conditions and positively correlated with root, shoot, and total dry matters, in both control and stress conditions (r2 = ranged from 0.589 to 0.961 in control and from 0.351 to 0.985 in stress). Of these, 25 accessions were assessed for estimation of genetic diversity, employing random amplified polymorphic DNA (RAPD) markers. A total of 210 RAPD bands, obtained with 32 primers, revealed high polymorphic information content (0.49) and marker index (4.41). Dendrogram analysis indicated close proximity among the accessions of S. scabra. These accessions were clustered in high similarity range (84.01–98.36 %). Accession IG-366A separated from other clusters at 85.62 % similarity level. RAPD marker system revealed 13 accessions exhibiting >90 % genetic similarity while the other accessions exhibited similarity ranging from 68 to 90 %. A higher level of genetic similarity which was also evident from the similar levels of TE, biomass production, root/shoot ratio, MDA, proline contents and drought tolerance index, indicated a cause–effect relationship among them. Results also indicated that among the accessions, S. scabra rate-reducing resistance allo-tetraploid lines were better suited for hard and cracking soils, under complete rain-fed condition.

Correlation of drought resistance in grass pea (Lathyrus sativus) with reactive oxygen species scavenging and osmotic adjustment

AbstractGrass pea (Lathyrus sativus L.), a legume crop in arid and semi-arid areas, is widely acknowledged as highly drought tolerant. We report here an analysis of grass pea and garden pea seedlings stressed with 20% polyethylene glycol 6000 (PEG) for five days. While leaf margins of grass pea curled inward after PEG stress, leaves of pea failed to display this trait. PEG inhibited the growth of grass pea less than that of pea. Hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulation increased in pea more than in grass pea. Greater accumulation of proline and soluble sugars alleviated osmotic stress injury to grass pea compared with pea. Moreover, PEG caused a significantly greater increase of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GPX) activities in grass pea compared to pea. These enzymes showed obvious up-regulation at the transcriptional level in grass pea leaves. Together, these data suggest that the accumulation of osmoprotectants and the improvement of oxidation resistance resulted in the higher drought tolerance of grass pea compared to pea.

Differential performance of two forage species, Medicago truncatula and Sulla carnosa, under water-deficit stress and recovery

The response patterns during water deficit stress and subsequent recovery of two forage species, Medicago truncatula and Sulla carnosa, were studied. After germination and pre-treatment, seedlings were individually cultivated for two months under two irrigation modes: 100% and 33% of field capacity. Measured parameters were plant growth, water relations, leaf osmotic potential, lipid peroxidation, and leaf inorganic (Na+ and K+) and organic (proline and soluble sugars) solute contents, as well as delta-1-pyrroline-5-carboxylate synthase (P5CS) and proline dehydrogenase (PDH) activities. Our results showed that under control conditions, and in contrast to roots, no significant differences were observed in shoot biomass production between the two species. However, when subjected to water-deficit stress, M. truncatula appeared to be more tolerant than S. carnosa (reduction by 50 and 70%, respectively). In the two studied species, water-deficit stress led to an increase in root/shoot ratio and leaf proline and soluble sugar contents, and a decrease in leaf osmotic potential. Enzymatic assay revealed that in the two species, P5CS activity was stimulated whereas that of PDH was inhibited under stress conditions. Despite greater accumulation of proline, sugar, and potassium in leaves of S. carnosa, M. truncatula was more tolerant to water deficit. This was essentially due to its capacity to control tissue hydration and water-use efficiency, in addition to its greater ability to protect membrane integrity. Following stress relief, M. truncatula and S. carnosa showed partial re-establishment of growth capacity.

Sulfur and Nitrogen Co-ordinately Improve Photosynthetic Efficiency, Growth and Proline Accumulation in Two Cultivars of Mustard Under Salt Stress

The potential of applied nitrogen (N) or sulfur (S) at 100 mg.kg-1 soil individually or in combination in the alleviation of 100 mM NaCl stress was studied in mustard (Brassica juncea L.) cvs. Alankar and Chutki. In general, salt stress decreased photosynthetic efficiency, nitrate reductase activity, N content and growth in both the cultivars, but the effect was greater in Chutki compared to Alankar. In contrast, proline accumulation increased under salt stress but to a greater extent in Alankar. The individual application of N and S protected the plants from salt stress, but combined N and S treatment was more efficacious in alleviating salt stress and more conspicuously in Alankar by limiting chlorophyll degradation, increasing N assimilation and proline accumulation. It was concluded that the cultivar Alankar was more responsive to individual and combined N and S treatments. However, the combined N and S application resulted in greater proline accumulation and alleviated salt stress effects on photosynthetic efficiency and growth.

Reactive oxygen species, ascorbate–glutathione pool, and enzymes of their metabolism in drought-sensitive and tolerant indica rice (Oryza sativa L.) seedlings subjected to progressing levels of water deficit

Water deficit for rice is a worldwide concern, and to produce drought-tolerant varieties, it is essential to elucidate molecular mechanisms associated with water deficit tolerance. In the present study, we investigated the differential responses of nonenzymatic antioxidants ascorbate (AsA), glutathione (GSH), and their redox pool as well as activity levels of enzymes of ascorbate-glutathione cycle in seedlings of drought-sensitive rice (Oryza sativa L.) cv. Malviya-36 and drought-tolerant cv. Brown Gora subjected to water deficit treatment of -1.0 and -2.1MPa for 24-72h using PEG-6000 in sand cultures. Water deficit caused increased production of reactive oxygen species such as O2[Symbol: see text](-), H2O2, and HO[Symbol: see text] in the tissues, and the level of production was higher in the sensitive than the tolerant cultivar. Water deficit caused reduction in AsA and GSH and decline in their redox ratios (AsA/DHA and GSH/GSSG) with lesser decline in tolerant than the sensitive seedlings. With progressive level of water deficit, the activities of monodehydroascorbate reductase, dehydroascorbate reductase, ascorbate peroxidase (APX), and glutathione transferase increased in the seedlings of both rice cultivars, but the increased activity levels were higher in the seedlings of drought-tolerant cv. Brown Gora compared to the sensitive cv. Malviya-36. Greater accumulation of proline was observed in stressed seedlings of tolerant than the sensitive cultivar. In-gel activity staining of APX revealed varying numbers of their isoforms and their differential expression in sensitive and tolerant seedlings under water deficit. Results suggest that an enhanced oxidative stress tolerance by a well-coordinated cellular redox state of ascorbate and glutathione in reduced forms and induction of antioxidant defense system by elevated activity levels of enzymes of ascorbate-glutathione cycle is associated with water deficit tolerance in rice.

Plant growth promoting bacteria enhance water stress resistance in green gram plants

Plant growth promoting bacterial (PGPB) strains Pseudomonas fluorescens Pf1 and endophytic Bacillus subtilis EPB5, EPB22, EPB 31 were tested for their capacity to induce water stress related proteins and enzymes in green gram (Vigna radiata) plants. Among the different bacteria used, P. fluorescens Pf1 increased the vigour index, fresh weight and dry weight of green gram seedlings in vitro. Quantitative and qualitative analyses of stress-related enzymes indicated the greater activity of catalase and peroxidase in green gram plants bacterized with P. fluorescens Pf1 against water stress when compared to untreated plants. The greater accumulation of proline was recorded in Pf1 treated plants compared to untreated plants. The pot culture study revealed the greater resistance to water stress by green gram plants treated with P. fluorescens Pf1 compared to untreated plants. The greater activity of stress-related enzymes in green gram plants mediated by PGPB could pave the way for developing drought management strategies.