Accelerated Sugar Accumulation and Ripening of Loquat Fruit by Exogenously Applied Ethylene

Just before the coloring of loquat (Eriobotrya japonica Lindl.) fruits, each fruit on the tree was covered for 2 to 3 days with a polyethylene bag containing Ethylene Sieve, which evolved ethylene by moisture. Sugar content per fruit at this stage was less than 10% of that in the fully mature fruit. The content in the treated fruit increased more rapidly than that in the control. Ethylene sharply decreased the titratable acid content in the treated fruit, while that in control still increased or remained little changed. Activities of sorbitol-6-phosphate dehydrogenase and NADP-malic enzyme were enhanced during natural ripening of loquat. In the treated fruit, these enzyme activities bagan to rise earlier than in control. Change in rind color became already visible 2 to 3 days after covering the fruit, and chlorophyll content rapidly fell. The treated fruit reached maturity 4 to 11 days earlier than the control. The results were discussed in reference to ethylene effect on sugar accumulation in fruit tissues.