HIGH LIGHT-INDUCED UNSTACKING OF THYLAKOIDS AND RANDOMIZATION OF PIGMENT-PROTEIN COMPLEXES OF CHLOROPLAST

Using absorbance changes at 540 nm and the per cent chlorophyll in 10K pellet after digitonin fractionation as the criteria of thylakoid sta cking, high light induced unstacking of thylakoids and randomization o f pigment protein complexes of chloroplast was characterized. Cation-i nduced increase in absorbance at 540 nm was abolished when chloroplast s were exposed to high light Also, the high light induced decrease in absorbance at 540 nm was more pronounced in sow salt chloroplasts as c ompared to the decrease in 540 nm absorbance in chloroplasts isolated in high salt. The decrease in the fraction of chlorophyll in digitonin fractionated 10K pellet was much more than the decrease in chlorophyl l In 10K pellet from high salt chloroplasts exposed to high light Thes e results suggest that high light causes unstacking of thylakoids.