The effects of drought stress and brassinosteroid solution spray on some morphological, physiological and biochemical characteristics of wild pear (Pyrus biossieriana Buhse

In order to investigate the effects of different levels of drought stress and application of brassinosteroid on some growth, physiological and biochemical characteristics of wild pear (Pyrus biossieriana Buhse) seedlings, an experiment was conducted in greenhouse in factorial form based on fully random pattern with three replications. Experimental treatments included different levels of drought stress (Control, field capacities of 75, 50 and 25%) and different concentrations of brassinosteroids (0, 3 and 10 mM). In this experiment the characteristics of dry weights of leaf, root, and stem, plant height, relative humidity content, electrolyte leakage, chlorophyll a, chlorophyll b, carotenoid, proline, soluble suagrs, malondialdehyde and hydrogen peroxide were investigated. The result shown that the drought stress cause significant reduce in dry weight of leaf, root, and stem, plant height, relative humidity content, and carotenoid; but brassinosteroid resulted in significant increase in these characteristics. Interaction brassinosteroids application in 10 mM and in 25% FC of drought stress condition showed the high level of soluble suagrs, proline, and hydrogen peroxide. It seems that in stress condition brassinosteroid application improved drought tolerance of the plant by increasing the concentration of osmolites such as soluble sugars and proline and therefore it succor to maintaining osmotic pressure in cells and increasing hydrogen peroxide production.