Variation in leaf photosynthetic response of rice genotypes to post-anthesis water deficit

Abstract

Variation in the response of six diverse rice genotypes to imposed water stress was investigated in terms of leaf photosynthetic traits and leaf water potential measurements (Ψleaf) during and following a period of water stress. The Ψleaf reduced from 0 days up to 6th day of irrigation deprivation and the reduction in Ψleaf was more pronounced in Swarna and minimum in PA-6201. A gradual recovery in Ψleaf was observed in all the tested varieties after re-irrigation. Similarly, water stress significantly reduced rate of photosynthesis (P N), stomatal conductance (gs), transpiration (E) and internal CO2 concentration (C i). Significant differences were noticed amongst the varieties in their response to water stress. The P N partially recovered in all tested varieties after re-irrigation. Vandana recorded greater recovery (65 %), where as the recovery was only 32 % in Sugandha Samba. Water stress (6 days of irrigation deprivation) significantly decreased the mean Chl a, Chlb, total chlorophyll and total carotenoid content. However, a marginal increase in total chlorophyll was observed under water stress in Vandana and N-22. Water stress had no significant effect on maximum photochemical efficiency (F v/F m) for all the tested varieties. However, in Sugandha Samba and Swarna a significant reduction was noticed. Water stress reduced the efficiency of excitation capture (ᶲe), in vivo quantum yield of PSII photochemistry (ᶲPSI), coefficient of photochemical quenching (qP) and increased the coefficient of non-photochemical quenching (qN). The data on photosynthetic traits and chlorophyll fluorescence parameters indicate that Vandana, N-22, DRR-Dhan-38 and PA-6201 which maintained relatively higher, Ψleaf, PN and gs under water stress and could also maintain high values of photochemical efficiency (Fv/Fm, ᶲ e, ᶲPSI and ETR) than Sugandha Samba and Swarna and the genotypic differences in the response of PSII activity could be exploited as traits for the selection of drought tolerant rice genotypes.