リンゴ果実の貯蔵性に及ぼす施用窒素, カリウムの影響

Abstract

The effect of nitrate and potassium fertilizers on the quality of apple fruit during storage was investigated.Seven year-old apple trees (Malus pumila Mill. cv. Jonagold) on Malus pruniforia rootstocks were grown in water culture solution of 0.3, 1.0 and 4.0mM nitrate. High nitrate concentration in the solution increased the yield, weight and sugar content of the fruit, but decreased firmness and acid content. It also enhanced ethylene evolution and NADP+-malic enzyme activity in the fruit during storage. Four year-old apple tree (Malus pumila Mill. cv. Fuji) on M9 rootstocks were grown in water culture solution of 1, 10 and 25mM potassium. The yield and weight of the fruit increased by growing the trees in culture solution of high potassium concentration, while firmness decreased. High potassium concentration in culture solution suppressed ethylene evolution and NADP+-malic enzyme activity and reduced acidity and decreased firmness in the fruit during storage. After storage at 0°C for 5 months, the quality of fruit grown with culture solution of high potassium concentration was superior to that with low potassium. Both high potassium and low nitrate concentrations in culture solution increased the potassium concentration in the fruit and storability of the fruit. This may indicate that the potassium concentration in the fruit is related to the storability of the fruit.