Effect of NaCl and exogenously supplied ABA on xanthophyll cycle pigments and energy dissipation in rice plants under high light stress

Abstract

In the present study rice (Oryza sativa L. Cv. Jyothi) plants grown in the shade and direct sunlight were subjected to salt stress (100 Mm) or fed with Aba (10 Mm) through roots to investigate their influence on the light-dependent Z formation and energy dissipation. plants (both -Nacl/+Nacl and -Aba/+Aba) were then treated with high light by exposing them to direct sunlight (1,200– 2,200 mu Mol M-2 S-1 Pfd). Leaf samples were collected for chlorophyll fluorescence measurements, pigment and Aba analysis at different intervals during the exposure. Results show plants subjected to salinity and high light stress showed an increase in the endogenous Aba level while Z was absent. Fv/Fm and Qn remained more or less same in plants grown with Nacl and photoinhibited and plants grown without Nacl and photoinhibited. Neoxanthin (Nx) content were much higher in salt grown plants but declined initially after onset of sun light treatment but increased after longer duration of the exposure. When plants were grown with exogenously supplied Aba and subsequently exposed to sunlight most of the V was made available for conversion to Z and this was correlated with higher level of Qn and better photoprotection.