カキにおけるNAAの摘果機構について (第2報)

Abstract

This experiment was carried out to obtain further information on the endogenous factors related to the thinning action of NAA in persimmon.Limbs of adult trees of‘Fuyu’were separately sprayed with NAA at 50ppm at various stages of fruit growth from 5 to 120 days after full bloom (F. B.). Each treatment was replicated five times. Fruit drop in the NAA-treated and non-treated (control) limbs was surveyed throughout the season. Further, fruits collected just prior to and 2 days after each NAA application were assayed for the activity of GA-, IAA-and ABA-like substances, peroxidase and IAA-oxidase in fruit tissue, and the activity of pectinase and cellulase in the abscission zone between the fruit and calyx tissues.Natural fruit drop occurred between 10 and 35 days after F. B. displaying two peaks about 20 and 30 days after F. B. NAA was effective for promoting fruit drop only when it was applied less than 30 days after F. B.The NAA applications between 10 and 20 days after F. B. were especially effective in stimulating fruit drop in company with rapid reduction in GA-and IAA-like substances and also with the increase in ABA-like substance, peroxidase and IAA-oxidase in the fruit tissue. Pectinase activity in the abscission zone did not exhibit any measurable changes associated with either natural or NAA-induced fruit drop. The level of cellulase in the zone, however, was extremely high during the time when natural fruit drop was observed, and it tended to be raised by the NAA applications effective for promoting fruit drop.