Studies and Applica tions of 12MCP on Delaying Ornamenta l Crops Senescence Effects of 1-methylcyclopropene on Postharvest Physiology and Cell Ultrastructure of Pollination-constant and Non-astringent Persimmon DuringStorage Effects of 1-methylcyclopropene on Postharvest Physiology and Cell Ultrastructure of Pollination-constant and Non-astringent Persimmon DuringStorage