Differential response of wheat genotypes to long term salinity stress in relation to oxidative stress, antioxidant activity and osmolyte concentration

ions and to some extent Cl and SO 4 2 of Mg 2+ and nutrient imbalance caused by excess of Na + and Cl ions. Salinity stress response is multigenic, as a number of processes i n- volved in the tolerance mechanism are affected, such as var ious compatible solutes/osmolytes, polyamines, reactive oxygen species and antioxidant defence mecha- nism, ion transport and compartmentalization of inj u- rious ions. Various genes/cDNAs encoding proteins involved in the above-mentioned processes have been identified and isolated. The role of genes/cDNAs e n- coding proteins involved in regulating other genes/ pro- teins, signal transduction process involving hormones like ABA, JA and polyamines, and strategies to i mprove salinity stress tolerance have also been di scussed. EXCESS amount of salt in the soil adversely affects plant growth and development. Nearly 20% of the world's cul- tivated area and nearly half of the world's i rrigated lands are affected by salinity 1

Physiology and molecular biology of salinity stress tolerance in plants

Differential responses of lipid peroxidation and antioxidants in the leaves of drought-tolerant P. acutifolius Gray and drought-sensitive P. vulgaris L. subjected to polyethylene glycol mediated water stress

Protective role of antioxidant enzymes under high temperature stress.

Changes in antioxidant activity in sub-cellular fractions of tolerant and susceptible wheat genotypes in response to long term salt stress

An experiment was conducted with three wheat genotypes differing in their sensitivity to moisture and/or temperature stress to study the relationship of the chloroplast antioxidant system to stress tolerance. Both moisture stress and temperature stress increased glutathione reductase and peroxidase and decreased membrane stab-iltty, chlorophyll content and chlorophyll stability index in all genotypes. Under moisture stress. DL 153–2 showed the highest membrane stabihty index, chlorophyll content, chlorophyll stability index, glutathione reductase activity and peroxidase activity. However, under elevated temperature conditions, HD 2285, and to a lesser extent DL 153–2, showed higher membrane stability, chlorophyll content and chlorophyll stability index and activities of glutathione reductase and peroxi-dase. Raj 3077, which is sensitive to both drought and temperature stress, showed the lowest membrane stability, chlorophyll content and chlorophyll stability index and glutathione reductase and perosidase activity under elevated temperature as well as drought conditions. Thus, it can be concluded that tolerance of the genotype to moisture and/or temperature stress is closely associated with its antioxidant enzyme system.

Tolerance of Drought and Temperature Stress in Relation to Increased Antioxidant Enzyme Activity in Wheat

The role of plant antioxidant system in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in a general increase in lipid peroxidation (LPO) and decrease in membrane stability index (MSI), and contents of chlorophylls (Chl) and carotenoids (Car). Antioxidant enzymes like glutathione reductase and ascorbate peroxidase significantly increased under water stress. Genotype C 306, which had highest glutathione reductase and ascorbate peroxidase activity, also showed lowest LPO and highest MSI, and Chl and Car contents under water stress in comparison to susceptible genotype HD 2329, which showed lowest antioxidant enzyme activity as well as MSI, Chl and Car contents and highest LPO. HD 2285 which is tolerant to high temperature during grain filling period showed intermediate behaviour. Thus, the relative tolerance of a genotype to water stress as reflected by its comparatively lower LPO and higher MSI, Chl and Car contents is closely associated with its antioxidant enzyme system.

Stress induced injury and antioxidant enzymes in relation to drought tolerance in wheat genotypes

Measurement of ion leakage as a screening technique for drought resistance in wheat genotypes

Metabolic activity and grain yield under moisture stress in wheat genotypes.

An experiment was conducted during winter season of 1989-90 and 1990-91 to study the effect of triadimefon on moisture stress in 'C 306" 'HD 2428' and 'HD 2329' genotypes of wheat (Triticum aestivum L. emend, Fiori & Paol.). Moisture stress decreased the relative water content (26%), transpiration (82%), chlorophyll (29%) and protein (27%). Triadimefon further reduced the transpiration and increased the relative water content and membrane stability under both the conditions. The effect of triadimefon was more in drought·tolerant genotypes 'C 306' than the susceptible' HD 2428'. Significant incrcase was also observed in chlorophyll content (24%) and protein content (56%) in triadimefon·treated plants. There was increase in tillers/plant, green leaves/plant and leaf area/plant, though the individual leaf size was slightly reduced by triadimefon application. Triadimefon 1 000 ppm significantly increased the yield (13%), grains/ear (10.5%), 1000-grain weight (8%) and harvest index (13%). The stimulatory effect was more in drought tolerant genotype than in suspectible one in post as well as in field under moisture stress.

D S Shukla

Papers

Tolerance of Drought and Temperature Stress in Relation to Increased Antioxidant Enzyme Activity in Wheat

Stress induced injury and antioxidant enzymes in relation to drought tolerance in wheat genotypes

Measurement of ion leakage as a screening technique for drought resistance in wheat genotypes

Metabolic activity and grain yield under moisture stress in wheat genotypes.

Effect of triazole - triadimefon on tolerance to moisture stress in wheat (Triticum aestivum) ABSTRACT