مشخصات پژوهش

An experiment was carried out to evaluate the effect of various concentrations of Mg (0, 1, 2, 3 and 4 mM) in the nutrient solution and shading (0 and 50%) on growth, yield, fruit quality and physiological properties in hydroponically grown cucumber (Cucumis sativus L. cv. Nagen 792). By increasing Mg concentration in both shaded and unshaded plants, the total plant leaf area and dry weight of leaves increased, whereas specific leaf weight decreased. The highest yield in terms of fruit weight and number per plant in both shaded and unshaded plants were obtained in 3 mM Mg treatment; yield in shaded plants was 57% lower than in unshaded plants. Increased Mg concentration drastically increased Mg content of the leaves and fruits and reduced K and Ca content, especially in shaded plants. Leaf and fruit concentration of Mg increased drastically while K and Ca decreased with increasing Mg in the nutrient solution. The ascorbate peroxidase (APX) and peroxidase (POX) activity in the leaves was decreased by increasing Mg concentration and the highest activity of both enzymes was observed in Mg deficient plants and was more pronounced in unshaded plants. Leaf soluble sugars and starch content were decreased with increasing Mg concentration in the solution, especially in shaded plants. Lower Mg concentration in the nutrient solution significantly increased total free amino acids (FAA) in the leaves. In general, Mg requirement of cucumber plants likely increases with light intensity. Thus, higher concentration of Mg (3 mM) in the nutrient solution was the most favorable for cucumber plant growth and function grown in hydroponics.