Salt Stress and Homobrassinosteroid Interactions during Germination in Barley Roots

Potential alleviation effects of Homobrassinosteroid (HBR) (0.5 and 1 mu M HBR) on root germination, cell division and antioxidant system enzymes (superoxide dismutase and catalase) of barley (Hordeum vulgare L. cv. 'Hilal') roots grown under different salt concentrations (150 mM and 250 mM) were investigated during 48 and 72 h at dark with their controls. Salt applications decreased primary root lengths, seminal root lengths, number of roots from one seed, mitotic activity and induced mitotic abnormalities. In addition, salt application decreased protein content but increased enzyme activities both at 48 h and 72 h when compared to control. Roots treated with HBR enhanced root lengths and root number. HBR-treated roots showed more mitotic activity, mitotic abnormalities and significant enlargements at the root tips when compared to controls and only salt-treated samples. Salt + HBR applications stimulated root lengths and showed more mitotic activity and mitotic abnormalities when compared to only salt-treated samples. Salt application increased superoxide dismutase and catalase activities both at 48 h and 72 h. However, HBR application decreased total soluble protein content and increased enzyme activities especially at 48 h compared to control. Depending on concentration and timing, salt + HBR treatments showed varying results in total soluble protein content and enzyme activities. There was also a significant change in protein banding patterns of experimental groups separated by SDS-PAGE. These findings are expected to contribute to understanding of how HBR affect barley roots grown under different salt concentrations.