Impact of elevated temperatures on water status, membrane integrity and antioxidant activity in flag leaves of wheat varieties (Triticum aestivium) sown at differential time intervals
T Chandra, J P Jaiswal, A Dubey, S C Shankhdhar, D Shankhdhar
Flag leaf is considered as powerful source of assimilates in wheat (Triticum aestivium) which helps in translocation of photosynthates in developing grains. However, its performance is afflicted by elevated temperatures, resulting reduced assimilate supply. Delayed sowing in wheat causes sudden elevation in air temperatures during various growth stages of wheat life cycle which disturbs flag leaf performance and reduces grain yield & quality. Researches shows that delayed sowing causes reduction in grain yield by 60 kg ha-1. Therefore, identifying varieties with improved flag leaf performance even under elevated temperature conditions is a need of hour, to minimize the yield loss due to delay in sowing conditions. In this context performance of flag leaves in eight wheat varieties (UP2628, HD3086, UP2967, UP2784, UP2526, UP2565, UP2748 and HD3059) sown at different time intervals were analyzed. As a result of delayed sowing, an elevation of 5ºC, 1.45ºC, 4.07 ºC and 3.71ºC in average air temperature at tillering, heading, anthesis and grain filling were registered. At the time of anthesis, water status and stability of membrane in flag leaves were found hampered upto 48.46% and 63.96% due to elevated temperatures. The increment in lipid peroxidation (79.66%) activation of antioxidant defense system (150% & 340%) also started off while during grain filling, water status (48.49%) and stability of cell membrane (69.03%) found more disturbed with much increase in lipid peroxidation (69.62%) was seen. However, the antioxidant defense system (SOD and CAT) also found activated (72.73% and 108.81% respectively) under elevated temperatures in compared to normal sowing conditions. The flag leaves of wheat varieties UP2565 and UP2748 showed heat adaptive response &considered as good performer under elevated temperatures and can be suggested as a promising source for further use in selection of heat-tolerant wheat genotypes.