Endogenous hormone and nutritional ingredient of pendulous characteristics of Cunninghamia lanceolata var. Luotian

Cunninghamia lanceolata var. Luotian (herein, Luotian), a natural variety of Cunninghamia lanceolata (Chinese fir, herein Lanceolata), shows great potential for agricultural protection short-period and high density plantations because of its narrow, pointed, tower-shaped crowns, thin braches and older drooping branches that die naturally at 6-7 years old. The physiological mechanisms of the pendulousness and the natural death of the branches are still unclear. To investigate these mechanisms, phytohormone levels and nutritional ingredients of different positions of branches in Luotian and Lanceolata were determined. Phytohormone analyses showed that IAA and ZR played critical functions on the branch initial growth, and that GA3 was related to bending of branches. Meanwhile, ABA may enhance abscission of the branches in Luotian. Nutritional ingredient analyses showed that the accumulation of nutritional ingredients in Luotian and Lanceolata were consistent with the morphology of their branches. An integrated analysis implied that phytohormones had a strong influence on pendulous characteristics by interacting with other factors. This study helps to elucidate the mechanism governing the pendulous trait and provides theoretical basis and technical support for its cultivation, introduction, plantation management and genetic improvement.