The Effects of plant growth regulators on oxidative stress

SUMMARY The Effects of Plant Growth Regulators on Oxidative Stress In this study, maize (Zea mays L.) seedlings exposed to paraquat (PQ) after pretreated with spermine (SPM), putrescine (PUT), benzyladenine (BA) and gibberellic acid (GA3) were examined to find out the changes of relative water content, total chlorophyll, soluble protein, some antioxidant substances (carotenoid and ascorbic acid) and enzyme (superoxide dismutase (SOD), peroxidase (POD) and glutathione reductase (GR)) activities with some endogenous plant growth regulators (GA, indolacetic acid (IAA), zeatin (Z), abscisic acid (ABA)) levels. Relative water, total chlorophyll and soluble protein contents in maize seedlings treated with PQ decreased significantly, while the decreases in these parameters were determined to prevent in seedlings pretreated with plant growth regulators (PGR). Also, it was found that the decreases caused by PQ in the levels of antioxidant substances such as carotenoid and ascorbic acid were significantly prevented in seedlings pretreated with PGR. SOD and POD activities were recorded to increase, GR activity increased at first and then decreased in seedlings exposed to PQ. In seedlings pretreated with SPM, PUT and BA, SOD and POD activities were determined to increase depending on the concentrations applied and not to change significantly the activities of these enzymes in GA3 treatments. Generally, GR activity increased in the seedlings pretreated with PGR. Also, PQ treatment decreased the levels of endogenous GA, IAA and Z, while increased ABA level. The decreases in the levels of GA, IAA and Z were prevented in the seedlings pretreated with PGR, even the amounts of some endogenous PGR increased significantly. ABA content was not markedly different as compared with control seedlings (except 0.2 mM SPM and PUT). According to the present results, it can be said that PGR might positively stimulate the tolerance mechanisms of plants against the factors caused oxidative stress. Key Words: Paraquat, Oxidative Stress, Spermine, Putrescine, Benzyladenine, Gibberellic Acid, Superoxide Dismutase, Peroxidase. vn