EFFECT OF WATER AND UV-B STRESSES ON ANTIOXIDANT SYSTEMS IN TOBACCO GENOTYPES

Abstract

The role of antioxidants in protecting the tobacco cultivars having different response to water stress from deleterious effect of oxidative stress induced by water and UV-B stress was investigated. The cultivars of tobacco to two cultivated species were able to adopt themselves to water and UV-B stresses by increasing the activities of antioxidant enzymes. The differences in the peroxidase (POX) activity among the tobacco cultivars were significant under both stresses except in the variety Pyruvithanam which was susceptible to water stress. The cultivars Kanchan, Banket A1 and Ratna (N. tabacum) showed maximum increase in POX activity in response to both stresses. Polyphenol oxidase activity increased significantly in all the cultivars in water stress whereas it increased non-significantly under UV-B stress. Thiobarbituric acid reactive substances (TBARS) content varied considerably under stress condition. A coordinated response involving the high activity of SOD, CAT, POX and ascorbic acid is triggered in the varieties Kanchan, Banket A1 and Ratna which are having water stress tolerance to withstand the oxidative stress.