Variability in gas exchange attributes of wheat RILs subjected to high temperature stress

High temperature above the optimum has a drastic effect on the stomatal activity and gaseous exchange which ultimately affect the yield and yield attributing traits. In this study, the Net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), and intrinsic water use efficiency (iW_T) on flag leaves of 100 recombinant inbred lines of bread wheat derived from the cross of WH1021 (heat-tolerant) and WH711 (heat-sensitive) were evaluated. Recombinant inbred lines and both parents were assessed for various gas attributes under two sowing dates i.e., normal (17.11.2015) and late sowing (27.12.2015). The temperature persisted normal from December, 2015 to February, 2016 and there was a consistent rise in temperature in the last week of March. Measurements were made at anthesis and 10 days after anthesis. Average A, E, gs and iW_T decreased as the temperature increase. A contrasting difference was observed in timely sown and late sown at 10 days after anthesis for photosynthetic rate and transpiration rate. Decrease in stomatal conductance and water use efficiency was found with delayed sowing and high temperature. There results may prove useful in the selection of physiologically efficient heat-tolerant genotypes with higher rate of photosynthesis.