Complete defoliation is essential for tree peony reflowering in autumn to trigger sucrose metabolism and adjust source-sink balance in buds and leaves

•Partial defoliation fails to trigger bud development or reflowering in tree peony.•Complete defoliation triggers sucrose metabolism and rebalances of source-sink relationship.•The reflowering inducing was scarcely related to stress signal.•Photosynthesis itself may be not involved in this process, neither.•Transcriptional regulation of SUTs, SWEETs and INVs is involved in the process.