Analysis of the Cause of Shoot Apex Death in the Annual Growth Cycle of Castanea mollissima Blume cv.‘Xin 12'

摘要

Shoot apex death was observed in Castanea mollissima Blume cv. ‘Xin 12',using DNA degradation and changes in nuclear morphology as parameters. Thebuds in the shoot apex of this cultivar exhibited abscission and shoot apex interval death in the following year as a visible symptom of programmed cell death (PCD). The physiological mechanism of PCD in buds was studied by observation of the shoot apex, nuclear morphology and nuclear degradation. Extraction and staining of nuclei from buds in the shoot apex at various times showed that nuclear degradation occurred in the last ten days of July, prior to visible signs of bud abscission. From then on the nuclei degenerated quickly, and by the middle of August the Pl-stained nuclei had hardly any fluorescence. It was concluded that PCD had happened in the buds of the shoot apex in July during the annual growth cycle, so that the buds of side shoots developed into new branches in the next year.