Abstract Sugar apple (Annona squamosa L.) is a significant fruit in tropics due to its abundant nutrition and high commercial value. In order to explore the effects of pruning and illumination on the flowering of axillary bud, new and mature branches growing in the same year were selected as experimental materials treated by different pruning ways with different colors of plastic film bagging. Nature growing branches were served as control. The contents of N, P, K and carbohydrates in inducing flowering parts and flower buds in different periods and developmental stage were determined. The results showed that if the branches were not removed the leaves and petiole, axillary bud of these branches failed to flower. Axillary bud could flower only under the condition of leaf and petiole removed. qRT-PCR analysis showed that the expression of LYF (LEAFY) and AP2 (APETALA2) were up-regulated at high level (P＜0.05) in tissues with proper pruning. When shoots with tipping and leaf and petiole removal were bagged with different color plastic films, the flowering was comparable among the treatments. This result indicated that flowering was not affected by light wavelength. In addition, axillary bud under proper pruning could flower at different seasons. Meanwhile, the content of N, P, K, starch and total soluble sugars in the branches of treatment 1 decreased in the first phase and then increased in the later compared with the control. This experiment demonstrated that the presence of petiole inhibited the flowering of axillary bud, removal of the petiole induced flowering genes expression, which switched from vegetative to reproductive growth and then led to blossoming and bearing fruit. In the process of floral induction, processing branches could not carry out photosynthesis in the short term, which resulted in the main nutrient contents presenting the increase after decline. The flowering process was not affected by the influence of illumination and light quality differences. While the completion of the floral induction, normal light was needed to promote the normal growth of the new germination branches, which provided the guarantee to blossom. The results preliminarily reveal the mechanism of the flowering by the unique pruning way from the physiological and molecular levels, and provide theory basis and practical guidance to regulate flowering period and off-season production of sweetsop tree.
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