UV-B induced alterations in composition of thylakoid membrane and amino acids in leaves of Rhizophora apiculata Blume

Seedlings of Rhizophora apiculata were exposed to UV-B radiation at four doses equivalent to 10, 20, 30, and 40 % ozone depletion. The seedlings irradiated with high doses of UV-B had characteristic decline in contents of specific proteins with molecular masses of 33, 23, and 17 kDa. On the contrary, proteins of 55, 33, 25, 23, and 17 kDa were accumulated in the seedlings exposed to low doses of UV-B. The UV-B, in general, enhanced formation of saturated fatty acids and reduced unsaturated fatty acids, to a maximum extent of 88 and 26 %, respectively. The low dose of UV-B increased content of oleic acid by 9 %, and the high dose reduced it by 34 %. The high dose of UV-B enhanced the lipid peroxidation by 48 %, whereas the low dose of UV-B did not show any significant effect. The contents of amino acids such as aspartate, glutamate, asparagine, serine, glutamine, threonine, and histidine were increased in low UV-B doses by 53, 86, 142, 72, 3, 119, and 32 %, respectively; while in high doses they were reduced significantly.