A nutrient solution experiment was carried out to evaluate effects of different magnesium (Mg) oncentrations (0, 25, 50, 75 and 100 percent of magnesium concentration of Hoagland solution) on growth and hysiological characteristics of Iranian melons (Cucumis melo var. inodorus subvar. Khatouni). The experiment was done based on completely randomized design using plastic pots and sand culture. The results showed that SPAD value of leaves, plant leaf number, stem diameter, shoot fresh and dry weight, root fresh weight, chlorophyll b, carotenoids, protein, catalase and peroxidase activities were constantly increased by increasing Mg levels of nutrient solution until 75 or 100% Mg levels, while leaf area, petiole length, internodes length were highest in lower levels of Mg compared to full Mg of nutrient solution. Moreover, the leaf concentrations of nitrogen (N), phosphorus (P), potassium (K), magnesium, and iron (Fe), but not calcium (Ca), were increased by increasing magnesium concentration to full Hoagland nutrient solution Mg level.

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