Regulation of growth and physiological traits of cucumber (&ITCucumis sativus&IT L.) through various levels of 28-homobrassinolide under salt stress conditions

Brassinoids are plant steroidal hormones that are ubiquitous in the plant kingdom and regulate a wide range of physiological and stress responses. In a plastic tunnel pot bioassay experiment, three levels of 28-homobrassinolide (HBL) at 1, 3, and 5 mu mol L-1 were tested for growth and physiological attributes of cucumber cultivars 'Jinyou 1' (salt-sensitive) and 'Changchun Mici' (salt-tolerant), grown at various salt stress conditions (60 and 120 mmol L-1). Cucumber plants of both cultivars subjected to salt stress exhibited reduced growth attributes and altered antioxidant enzymes at 60 and 120 mmol L-1. However, the deleterious effects of salt stress were partially improved by HBL. The foliar application of HBL enhanced shoot and root fresh and dry weight and chlorophyII content at 60 and 120 mmol L-1 NaCl stress in Jinyou 1' and 'Changchun Mici', respectively. Homobrassinolide application also altered the antioxidant enzyme levels by increasing super oxide dismutase and peroxidase levels and decreased malondialdehyde content under 60 and 120 mmol L-1 stress in both plant cultivars. Overall results showed that HBL could enhance growth attributes, chlorophyII content, and antioxidant enzymes for both of the cultivars under mild and high NaCl stress.