Effect of drought stress on apple dwarf

Drought is one of the most important environmental stresses which affect most growth and physiological aspects of plants and causes huge damages to agriculture products every year. Considering the arid conditions of Iran, using methods like proper exploitation of water resources, planting resistant plants, identification of factors interfering in resistance of plants to drought stress and finding index or indices by which we can anticipate the sensetivity or resistance of a plant have a special importance. To select the resistant rootstocks and study the impacts of drought stress on physiological, biochemical and growth parameters responses of apple dwarf rootstocks, various levels of water stress were performed on one-year-old apple tree dwarf rootstocks, of cvs,Malling 9, Malling Merton 106, Azayesh , Gami Almasi and seedling rootstock as a control. Irrigation treatments were 1- Control : in this treatment plants was irrigated every three days at once 2- moderate drought : plants in this treatment was irrigated when soil water potential reach to -0/5 MPa (meqapascal) or five days at once 3- severe drought : plants in this treatment was irrigated when soil water potential reach to -0/1 MPa (meqapascal) or ten days at once. MPa (meqapascal) is a unit of atmospheric pressure which is used in place of bars and 1 MPa = 10 bar (kramer, 1988). This study was conducted at the west azarbaijan agriculture research center of Iran. A factorial experiment based on randomized complete block design was used. Measurment of water potential and relative water content in leaves be used as means for evalation of plant water situation. These parameters have correlation with different nature of plant morphology, biochemicalogy and physiology such as vegetative growth and production. In this study plant growth parameters, biochemical and physiological parameters and stomatal conductance in leaf were measured in young tree of four apple dwarf rootstocks with seedling rootstock as control that was cultured in 20 L plastic pots. Results showed that the drought stress caused significant reductions in plant growth parameters such as vegetative shoot growth, trunk area, leaf area, leaf number, root number,wet and dry weight of leaf, leaf water potential, relative water content, relative water loss, shoot diameter(Table.1) and physiological parameters including chlorophyll concentration, but under drought stress, physiological parameters including amount of free proline, soluble sugars and leaf temperature were increased (Table.2). Control, GA and M.9 rootstocks had greatest amount of free proline concentration, soluble sugars and leaf temperature respectively so were resistant to drought stress in comparison with other rootstocks.