Chlorophyll and Chlorophyll Fluorescence as Influenced by Combined Heat and Drought Stress in Rice

The present study was aimed to screen three rice genotypes (ADT 43,TKM 9 and N22) for combined heat and drought stress tolerance at panicle initiation (PI) and anthesis stage under rainout shelter. The genotype N22 was found to be the tolerant followed by TKM9 and ADT43 was observed to the susceptible based on the physiological traits such as chlorophyll content and chlorophyll fluorescence. Irrespective of genotypes anthesis stage stress brought about more severe yield reduction compared to stress at Panicle Initiation stage. Anthesis stagestresses caused reduction in chlorophyll content, chlorophyll fluorescence (Fv/Fm values) and finally yield. ADT 43 recorded chlorophyll content of (1.16 mg/g) and Fv/Fm value of (0.34) with 62.70% of yield reduction under stress, while N22 recorded higher chlorophyll content of (1.97 mg/g) and Fv/Fm value of (0.41) with 31.22% of yield reduction during anthesis stage stress. This conforms that these physiological traits can be used to screen rice genotypes to combined stresses.