EFFECT OF LOW-LIGHT ON PHOTOSYNTHETIC PIGMENTS, PHOTOCHEMICAL EFFICIENCY AND HILL REACTION IN RICE (ORYZA-SATIVA L.)

Photosynthesis and related functions in low light tolerant (CO 43 and Swarnaprabha) and low light susceptible (IR 20) rice varieties were me asured under shaded conditions and in normal sunlight. The increase in the contents of chlorophyl (chl) a, chl b, total chlorophyll and caro tenoids under low light treatment was more prominent in Swarnaprabha a nd CO 43 than that of IR 20. But a decreasing trend was observed in ch l a/b ratio in all the three cultivars due to predominant increase of chl b fraction. The decrease in ratio was less in Swarnaprabha and CO 43 than that of IR 20. Higher photochemical efficiency and photosynthe tic rate over IR 20 were maintained by Swarnaprabha and CO 43 grown un der shaded condition. Shading up to flowering stage enhanced the Hill reaction and during harvest stage induced a reduction in Hill reactivi ty in all the three varieties.