Effects of Calcium Concentration in Fertilizer Solution on Passion Fruit Quality

抄録

Less acid passion fruit has been increasingly demanded for fresh consumption. In this study, effects of Ca concentration in fertilizer solution on passion fruit quality were examined. Twenty-four passion fruit plants, grown in pots filled with river sand, were used. From June 27 to September 27, 2013, 1000 mL of fertilizer solutions, containing 0, 2, 4, or 8 mM Ca, were applied to the plants twice a week. A neutral salt, CaCl₂, was used so as not to affect pH of the sand media. Artificial pollination was conducted from June 28 to August 2 and the number of fruits per plant was regulated to be eight. Titratable acid content in juice (TA) decreased and total soluble solid content (TSS) increased as Ca concentration increased up to 4 mM. Juice content, fruit weight and dimensions were not affected by Ca fertilizer. At 8 mM, necrosis occurred on two of the six plants, and the leaves fell greatly. Fruit from the severely-damaged plants had higher TA and lower TSS than that from non-damaged plant. Leaf Ca content increased as Ca concentration in fertilizer solution increased. Leaf mineral contents except for Ca and Mn, were not affected. In conclusion, Ca application was effective to produce high quality passion fruit and fruit quality was the highest with 4 mM Ca concentration in fertilizer solution and 2.5 % of leaf Ca content, though necrosis occurred on some plants at 8 mM Ca treatment.