ニホンナシの花芽形成, 栄養成分並びに内生生長調節物質に及ぼす SADH 及び新梢誘引の影響

Abstract

In order to clarify the mechanism of flower bud formation in Japanese pear (Pyrus serotina Rehd.), the effects of SADH application and bending of shoots on nutrient elements and endogenous growth regulators in shoot tips and axillary buds were studied in relation to the differentiation and development of flower buds.1. SADH application or bending of each shoot in ‘Shinsui’ was carried out on June 10; after application of SADH shoot growth stopped one month earlier than in controls, and after bending, shoot growth stopped twenty days earlier than in controls.2. In both treatments there was a rapid increase in the number of nodes (scales and bracts) in axillary buds ten days after treatment. On June 30, twelve scales were formed, after which the first visible signs of flower initiation were found. Thereafter the flower buds differentiated and developed in both treatments. The final percentage of flower bud formation was about 60%.3. On the other hand in controls the number of nodes in axillary buds increased slowly, so that only a few of the first visible signs of flower initiation were found on July 30, which was one month later than in both treatments. Thereafter differentiation and development did not occur, so that the final percentage of flower bud formation was 15.2%.4. Both treatments led to a marked decrease in sorbitol and amino acid contents in the shoot tips, but to increases in axillary buds.5. Both treatments caused a decrease in IAA and cytokinin contents in shoot tips, but caused rapid increases in axillary buds.6. Both treatments markedly decreased the gibberellin content of shoot tips and axillary buds.From these results, it was suggested that flower initiation in Japanese pear is determined by the active state of buds, giving an increase in the number of nodes followed by formation of twelve scale. Endogenous growth regulators are closely involved in these processes, particularly gibberellin and cytokinin, which play a major role in flower bud formation.