CHANGE OF SOME OSMOLYTES ACCUMULATION IN WATER-STRESSED COLZA (BRASSICA NAPUS L.) AS AFFECTED BY 24-EPIBRASSINOLIDE*

Brassinosteroids are phytohormones possessing a wide spectrum of antistress activity. To see whether this hormone is able to ameliorate the effects of water stress, the effects of 24-epibrassinolise on plant growth, accumulation of osmolytes (proline, sugars and ions), lipid peroxidation and electrolyte leakage were investigated in Colza (Brassica napus L. cv. Fusia) plants which were under water stress. The seeds were sown in plastic pots containing sand, clay and peat (in a proportion of 1:1:1). Solution of 24-epibrassinolid at 10-7 M concentration containing 0.01% Tween-20 (polyoxyethylene sorbitan) was sprayed on leaves at intervals of 1, 2 and 3 weeks after sowing. Control plants were sprayed with 0.01% Tween-20, and water treatment was applied 26 days after germination, withholding water for 3 or 4 days. One month after sowing, plants were harvested. Lipid peroxidation and electrolyte leakage significantly increased under water stress, but when plants were pretreated with 24-epibrassinolid and put under water stress these parameters decreased, revealing that less oxidative damage occurred in this group. Proline and reduced sugars content was increased when 24-epibrassinolide were applied. FW and DW were significantly decreased under water stress. Water stress also increased the uptake of K and Ca, but the uptake of Na significantly decreased. 24- epibrassinolide considerably increased ions uptake by plants. Taken together, these results showed that 24- epibrassinolide alleviated the effects of water stress and increased the tolerance of plants to stress by increasing osmolytes accumulation and therefore could be used to improve crops in harsh conditions.