1994 Volume 62 Issue 4 Pages 867-875
The effects of defoliation and foliar application of gibberellic acid (GA) on the softening of Japanese persimmon (Diospyros kaki Thunb. 'Hiratanenashi'), exposed to ethanol fumes for 3 to 4 days after harvest, were investigated.
1. Fruit harvested from a tree that had shed leaves early due to declining vigour, softened 5 to 10 days before those from a healthy tree ; whereas, fruit from a tree growing in a plastic greenhouse which shed leaves even later in the season, were the slowest to soften.
2. Mature fruit on shoots which were defoliated on July 21 produced ethylene and sof- tened rapidly upon harvest.
3. Spraying bearing shoots on Sept. 7 with 50 ppm GA had no effect on ethylene production, but the treatment did inhibit fruit softening. Comparison between mature fruits harvested from unsprayed and GA-treated shoots, which were both defoliated 4 days after treatment, revealed that fruits from the unsprayed shoots softened, whereas those from the GA-treated ones did not. Thus, the GA-treatment reversed the effect of defoliation.
4. The dwarf rice bioassays by paper chromatography of extracts of mature fruit collected from shoots defoliated on July 21 revealed no activity, whereas, extracts of fruits from the control shoots promoted 2nd leaf sheath elongation of the rice seedling.
These results suggest that leaves on bearing shoots are important in the regulation of flesh softening of harvested mature fruit of Japanese persimmon Iliratanenashi treated with ethanol, and we propose that the GA, originating in the leaves and transported to the fruit, inhibits fruit-softening by blocking ethylene action.
