LOW IRRADIANCE STRESS TOLERANCE IN RICE (ORYZA-SATIVA L)

The effect of low irradiance on three rice cultivars (shade tolerant c vs. Swarnaprabha and CO 43 and shade susceptible cv. IR 20) was studie d. The large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase/ox ygenase with molecular mass of 55 kDa was reduced in cv. IR 20 grown u nder low irradiance (LI). Native protein profile studied showed, under LI, reduction in the contents of proteins with R(F) values 0.03, 0.11 and 0.37. Analysis of chloroplast polypeptides revealed an induction of light-harvesting chlorophyll-protein 2 (LHCP2) under shade. The ind uction was more expressed in cv. CO 43 than in cv. IR 20. Under LI, in vivo labelled protein bands in the molecular range of 26 - 27 kDa wer e induced. These proteins were highly turned over in the LI-grown plan ts of cv. CO 43 than in cv. IR 20. A signal for rbcL gene sequences in EcoRI digested lanes was also found. Isozyme analysis of peroxidase s howed an induction of a new band with R(F) 0.43 in cv. IR 20 subjected to LI.