生長抑制剤によるブドウの花ぶるい防止に関する研究(第4報)

Abstract

Cluster dipping with the solution of SADH at 2, 500ppm 26-20 days before full bloom significantly increased the number of seeded berries per cluster and of seeds per seeded berry in Kyoho grape in 1975, 1976 and 1977. Shoot pinching leaving 8 leaves per shoot about 10 days before full bloom had no effect on the set of seeded berries but significantly promoted the set of seedless berries in both 1975 and 1976. Though this treatment promoted the set of seeded berries in the next year, it was less effective than the treatment with SADH. Flower thinning removing shoulder and tip parts of cluster about 10 days before full bloom was applied in 1975 and 1976, which exhibited the promotive effect on the set of seedless berries alone in both years alike shoot pinching.The application of SADH depressed the growth of floret, particularly of ovary wall in size before and during bloom, whereas shoot pinching enhanced and flower thinning did not affect it in the same period. Pollen germination on agar media and either pollen germination or pollen tube elongation in intact style and ovary tissues were not influenced by any of the treatments.Though no treatment had consistent effect on gibberellin activity in florets before and during bloom in 1975 and 1977, cytokinin level was raised by SADH application in both years and by shoot pinching in 1977 alone. Protein N and total N contents in florets before and during bloom were increased by SADH application but they were reduced or not so much affected by shoot pinching. Total sugar content in the same period tended to be raised by either SADH application or shoot pinching except at the beginning of bloom when it was slightly decreased by SADH application in both years.From these results, it is suggested that SADH application before anthesis in Kyoho grape promotes the set of seeded berries probably due to the improvement in fertilization ability of ovules and the effect of SADH may be causally related with the increased activity of cytokinin in developing florets. Further, it is shown that shoot pinching and flower thinning, as opposed to SADH application, promotemainly the set of seedless berries presumably resulted from the nutritional stimulation of parthenocarpic tendency.