Abstract:

‘Nagafu 2’apple trees were sprayed with 1.5% and 3% glucose solutions at 25 days and 30 days after full bloom，respectively. Bud growth，endogenous sugar levels，starch content and activities of related enzymes in terminal spur buds were examined. Genes associated with sugar metabolism and flowering were studied by quantitative real-time PCR. The results revealed that glucose treatments increased bud size and fresh weight. The contents of sucrose，glucose and sorbitol were significantly higher than in the control during early stage of floweral bud differentiation，while starch increased generally，but the content of fructose significantly decreased during the whole period. The activities of sorbitol dehydrogenase，sorbitol oxidase，synthesis direction of sucrose synthase and sucrose phosphate synthase increased at different stages，while acid and neutral invertases，decomposition direction of sucrose synthase decreased. Carbohydrate accumulation in leaves was evident，and the activities of enzymes involved in sugar metabolism also changed similarly. Genes associated with sugar metabolism and two MdTPS genes in terminal buds all responded to glucose treatment. Furthermore，flowering genes like MdFT 1，MdFD，MdLFY，MdSOC 1，and MdAP 1 were significantly up-regulated，while the suppressor MdTFL 1 was down-regulated from beginning of floral induction.

Key words: Malus ×, domestica, glucose；flowering, soluble sugar, enzyme activity, gene expression