Biochemical effect of carbaryl on oxidative stress, antioxidant enzymes and osmolytes of cyanobacterium Calothrix brevissima.

Carbaryl is used in Indian agriculture for control of rice field pests and it is next to Benzene hexachloride in pesticide consumption. In present study, carbaryl (0, 10, 20, 30 and 40 mg/L) induced toxic effects were observed after 21 days exposure on a non target rice field biofertilizer Calothrix brevissima with special reference to oxidative stress, antioxidant enzymes and osmolytes. At 40 mg/L carbaryl the decrease in carotenoid, chlorophyll, phycobilin and protein were 63%, 43%, 40% and 40% respectively in comparison to control. Total carbohydrate, malondialdehyde, superoxide dismutase, ascorbate peroxidase, catalase and osmolytes showed enhancement at all the treated concentration. Increased amount of MDA (46% at 40 mg/L) indicated free radical mediated deleterious effect of carbaryl. Enhancement of SOD, APX, CAT and osmolytes in presence of carbaryl indicated their involvement in free radical scavenging. SOD, CAT and APX showed maximum activities (79%, 64% and 39% respectively) at 40 mg/L carbaryl. The order of enhancement in osmolytes was glycine-betaine (66%) > proline (54%) > sucrose (50%) at 40 mg/L which might be another adaptive defense strategy of the cyanobacterium against the pesticide.