RESUMO
The Present paper deals with the herbicide Butachlor (5,10 ,20,40 and 80ppm)-induced changes in physiological and biochemical parameters related to photosynthesis and defense systems in paddy field cyanobacterium Plectonema boryanum grown under laboratory conditions. Growth and photosynthetic pigments, i.e., chlorophyll a and carotenoids were adversely affected by Butachlor treatment and the inhibition was found to be dose dependent. The toxic effect of Butachlor was more pronounced protein; however, a considerable reduction in chlorophyll a, and carotenoids was also noticed. Furthermore, Butachlor with increasing doses accelerated the formation of active oxygen species, i.e., O2- and H2O2, in cells progressively. As a consequence of active oxygen species (AOS) generation in Butachlor -treated cells, the activity of superoxide dismutase (SOD) and peroxidase (POD) was enhanced considerably. Besides the accelerated action of enzymatic defense systems, Protein damage also showed an increasing trend with the rising concentration of Butachlor (5, 10, 20, 40 and 80 ppm).