Effect of enhanced UV-B radiation on germination,seedling growth and biochemical responses of Vigna mungo (L.) Hepper

The study focuses on the effect of supplemental uv-b radiation on germination,seedling growth,chlorophyll a and b contents,soluble phenols,anthocyanins,flavones contents,phenylalanine ammonia lyase (pal) activity and tyrosine ammonia lyase (tal) activity of mash-bean (vigna mungo (l.) hepper.). even though the germination velocity was substantially increased,the final germination percentage remained significantly suppressed by uv-irradiance. both root and shoot growth of the seedlings were markedly reduced by enhanced uv-b radiation. uv-b irradiation substantially decreased both chlorophylls a and b and the total amount of chlorophyll a plus b compared to controls. however,chlorophyll a/b ratio was generally elevated. remarkable accumulation of total soluble phenols occurred in response to uv-b radiation. pal activity increased markedly as a result of uv-stress in the beginning,subsequently,however,it declined,whereas,tal activity consistently increased over the controls following uv-b irradiation up to 8 days of treatment. the levels of anthocyanins and flavones increased in treatments over the controls as they provide a protective mechanism to uv-b radiations. in general,the growth and physiological responses to uv-b radiation were more pronounced at greater exposure period.