Changes of Mineral Composition in Leaves and Fruit with Fruiting of Muskmelon (Cucumis melo L.) in Circulating Hydroponics

We evaluated fruiting-associated changes in inorganic components in the leaves and fruit of muskmelon (Cucumis melo L.) during circulating hydroponics. The contents of chlorophyll a and b in leaves rapidly increased from the day of fertilization to 15 days after fertilization. However, as the harvest season approached, a marked yellowing with degreening was observed in the first node leaf of fruit-bearing branch. The rate of phosphorus content differed between main stem leaves and fruit-bearing branch leaves, showing a rapid increase 30 days or more after fertilization in the first node leaf of fruit-bearing branch. The rate of potassium content decreased in leaves nearer to fruit, showing a marked decrease in first node leaf of fruit-bearing branch as the harvest season approached. The rate of calcium content was higher in main stem leaves than in fruit-bearing branch leaves. The rate of magnesium content increased irre-spective of the location of leaves until the harvest season. Thus, the concentration of inorganic component in the leaves of muskmelon differed among the sites of leaves, and changes in each component were markedly affected by the growth of fruits, being more marked in leaf nearer to fruit. The yellowing with degreening observed in the first node leaf of fruit-bearing branch appeared to be due to potassium deficiency in the leaf.