Ethylene Evolution and Premature Drop in Passion Fruit (Passiflora edulis x P. edulis f. flavicarpa)

抄録

To determine the possible relation of ethylene evolution from fruit to premature drop in passion fruit, morphological changes and cellulase activity at the abscission zone (AZ) of passion fruit with the occurrence of fruit drop, acidity of the juice, and ACC (1-aminocyclopropane-1-carboxylic acid) content were measured using the fruit treated with distilled water (DW) and ethephon (100ppm) at 40 days after pollination (DAP). More than 20% of fruits of DW treatment dropped prematurely when total organic acid content (TOAC) of the juice was over 4.0 g 100mL^-1 at 65 DAP. A significant increase in ethylene evolution from fruit was observed at 65 DAP in DW treatment, which not only induced coloring of the pericarp and reducing acidity of the juice but also manipulated the increase in ACC content at AZ. This was also confirmed with the amplified results of ethephon treatment: an increase in cellulase activity at AZ was manipulated by ethylene evolution from fruit of ethephon treatment. It should be noted that in this study cellulase activity at AZ did not respond to ethylene evolution from fruit of DW treatment. There may be possibilities that other cell wall disassemble enzymes, rather than cellulase alone, are likely responsible for premature drop in passion fruit. Ethylene evolution from fruit triggered concerted increase in degrading enzymes’ activity at AZ faster than reduction of the juice acidity, which may cause premature drop in passion fruit.