Effects of different chlorine concentrations on antioxidant enzymes activity in three varieties of flue-cured tobacco

Salt stress due to chlorine is one of the limiting factors in plant growth. An increasing of antioxidative enzymes activity is a defensive response of salt stresses. In this research, the effects of four chlorine concentrations in irrigation water (10, 20, 40, 80 mg/l CaCl2) on the activities of enzymes peroxidase, ascorbate peroxidase and polyphenol oxidase and malondialdehyde content, total leaf protein, and peroxidase zymogram in three greenhouse tobacco varieties were investigated. The results showed that an increase in chlorine concentration up to 80 mg/l, peroxidase enzyme activity decreased in Cooker. The highest and lowest ascorbate peroxidase activities of all stressed varieties were seen in 40 and80 mg/l treatments, respectively. polyphenol oxidase activity induced in Kentucky and Virginia by 40 mg/l treatment and reduced under 80 mg/l treatment in all three varieties. The measurement of malondialdehyde content in Cooker showed that there was no significant difference among all treatments, except in 20 mg/l concentration which was increased. Malondialdehyde content decreased significantly in Kentucky in all treatments compared to control. Malondialdehyde content of Virginia also showed no significant difference, except in 20 mg/l concentration which was reduced. Total protein content of Kentucky and Virginia was reduced with increasing of chlorine concentration.