Stress Physiological Regulation and Flower Induction of Longan Trees

LI Hong;Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Science;

Fruit tree physiology;;Fruit tree nutrition;;Longan tree flowering induction;;Gibberellin-dependent pathways;;Cumultive growing degree-days

In tree flowering there were four pathways of flowering time regulations including vernalization,photoperiod promotion, autonomous self-flowering and gibberellin(GA_3)-dependent pathways in fruit trees.Longan(Dimocarpus longan L.) was one of the most important tropical fruits in the world, had the specific function of vernalization process that its flowering was promoted as plants sense exposure to the cold temperatures of winter. The objectives of the current study were to use the cumulative growing degree-days(CGDD) data to guide the induction of longan tree flowering in the gibberellin(GA_3)-dependent pathway. In recent years, increased winter temperatures inhibit flower bud formation and differentiation of the chilling-required longan trees. The unreliable flowering of longan trees under naturally environmental conditions were threatening the industry of this important tropical fruit. The study was conducted in the north areas of tropical Hainan Island during 2014-2015. In the study, the cumulative CGDD values of longan trees at the specific growth stages,determined from the previous studies, were used to guide the application times of flower induction products including the chemical oxydants(KClO_3), stilbene paclobutrazol(PP_(333)), plant growth regulator complex compound of mixing cytokinin-gibberellin(GA_3) and leaf mineral nutrients potassium dihydrogen phosphate(KH_2PO_4). The results showed that the CGDD guided applications have led to effectively regulate the vegetative growth of longan trees,promote physiological photosynthesis and induce flower bud formation for flowering. It revealed that in the 4-month long flower induction process, inducting the vegetative growth to reproductive growth was the most important key point of whether or not longan trees could flower. The use of CGDD information in the GA_3 signaling pathway could accurately result in promoting the transformation of longan tree development status from vegetative growth to reproductive growth during the flower induction process, which could regulate flowering time for chilling required tropical and subtropical fruit trees in the winter climate warming environments.