Enhancement of salt tolerance in sugarcane by ascorbic acid pretreatment
Ascorbic acid is a non-enzymatic antioxidant which plays an important role in the activation of biological defense mechanisms. The effect of 24 h ascorbic acid (0.5 mM) pretreatment was observed on subsequent growth and development of callus cultures as well as in vitro-grown plants of Saccharum sp. hybrid (cvs. HSF 240 and SPF 234). After pretreatment, callus cultures of HSF 240 were transferred to 80, 100 and 120 mM sodium chloride (NaCl) while those of SPF 234 were subjected to 100, 120 and 140 mM NaCl concentrations. The in vitro-grown plants were also transferred to the saltcontaining media (0 to 160 mM; nine treatments) after ascorbic acid pretreatment. Ascorbic acid pretreatment to callus cultures resulted in more browning and necrosis. Pretreated in vitro-grown plants of both the sugarcane cultivars survived higher NaCl level and showed much less yellowing of leaves as compared to non-pretreated controls. Ascorbic acid pretreatment to in vitro-grown plants of cv. HSF 240 had a significant effect on catalase and peroxidase (POD) activities while in cv. SPF 234 a significant effect on root length, soluble protein contents as well as antioxidant enzyme activities was recorded. Hence both morphological as well as biochemical parameters studied during the present work suggested that ascorbic acid pretreatment of in vitro-grown sugarcane plants may enhance their salt tolerance.
Key words: Antioxidant enzymes, callus, protein content, salt stress.