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Abstract
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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.
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