Effect of non-ionising radiations on nitrogen fixing cyanobacterium Hapalosiphon stuhlmannii and photosynthetic green alga Scenedesmus quadricauda subjected to heavy metal stress.

Abstract

A study has been made, under controlled conditions, to investigate the influence of the non-ionising radiations namely Ultraviolet (UV) and Infrared (IR) on the morphological as well as the physiological variables such as the dry weight, chlorophyll pigments and protein content of the cyanobaterium Hapalosiphon stuhlmannii Hieron. and the green alga Scenedesmus quadricauda (Turp.) de Breb. exposed to chromium and nickel. The cultures of both the algae treated with different concentrations of chromium and nickel individually were exposed to a dose of 15 mW m(-2) nm(-1) of either UV or IR radiations. It was noted that distinct morphological variations were registered in the case of both the organisms. Though both UV and IR had inhibitory effect on the growth of the organisms, but interestingly UV had more inhibitory effect on the blue green alga H. stuhlmannii whereas IR had more inhibitory effect on the green alga S. quadricauda. It may be observed that the differential sensitivity of H. stuhlmannii and S. quadricauda towards UV and IR radiations noted in the present study seems to be due either to the variation in the intrinsic composition of the cell walls and/or to the preferential binding of the metals to the different algal cells.