Effect of water stress on photosynthetic attributes, membrane stability and yield in contrasting wheat genotypes

The effect of water stress on physiological parameters and yield components of drought tolerant (C-306) and drought sensitive (HD 2329) wheat genotypes was investigated under pot culture conditions. The stress condition was created at tillering, anthesis and post anthesis stages by withholding water supply for a period of 8 days. Water stress reduced the net rate of photosynthesis, transpiration and stomatal conductance in both the genotypes. Internal CO₂ concentration increased significantly under water stress conditions. The reduction in relative water content and membrane stability index was significantly higher in HD 2329. The chlorophyll and carotenoid content decreased whereas sugar and proline content increased under water stress in both the genotypes. Genotype C-306 registered lesser reduction in leaf area, grain number, spikelet number, 1000-grain weight and harvest index in response to water stress. HD 2329 exhibited higher grain weight per plant under optimum irrigation (control) but under water stress C-306 showed 19% more grain weight per plant. It is suggested that the drought tolerance mechanism exist in wheat genotype C-306 owing to its better management of gas exchange parameters, stomatal regulation, membrane stability, photosynthetic pigments and osmotically active metabolites, particularly at anthesis stage.