H. Li - Institute of Crop Germplasm Resources, Guizhou Academy of Agricultural Sciences，GuiYang, GuiZhou, ۵۵۰۰۰۶, China.
X. Kang - Hainan ZhongYi New Materials Research Institute Co., Ltd., SanYa, ۵۷۲۰۲۵, China.
C. Liu - Institute of Biotechnology, Guizhou Academy of Agricultural Sciences, Gui Yang, Gui Zhou, ۵۵۰۰۰۶, China.
H. Chen - Institute of Crop Germplasm Resources, Guizhou Academy of Agricultural Sciences，GuiYang, GuiZhou, ۵۵۰۰۰۶, China.
J. Huang - Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, College of Tropical crops, Hainan University, HaiKou, ۵۷۰۲۲۸, China.

Ethephon was widely used in rubber tree plantation to stimulate latex production. Numerous studies demonstrated that ethephon treatment prolongs the flow of the latex and promotes latex regeneration in the trunk of mature rubber tree seedlings. However, how rubber tree leaves responded to ethephon treatment on the trunk is still unknown. We used rubber tree seedlings to detect the physiological response of leaves after the trunk treatment with ethephon. The photosynthetic rate, the sugar and starch content, as well as the enzyme activities involved in sugar metabolism were measured after ۰, ۱۲, ۲۴, ۳۶ and ۴۸ hours with ۰.۶% ethephon treatment. The result demonstrated that ethephon treatment increased latex production on the trunk, while the net photosynthetic rate, transpiration rate, and stomatal conductance in leaves were significantly reduced. At the same time, sucrose decreased significantly with concomitant slight increase in glucose and fructose. Also, the enzymatic activities of Sucrose Phosphate Synthase (SPS), Sucrose Synthase (SS) and Neutral/alkaline Invertase (NI) increased significantly after ethephon treatment. Ethephon treatment affected the starch content, but did not change the composition of starch in rubber tree seedlings leaves; the overall starch changing pattern was similar to that of sucrose in leaves. It can be concluded that ethylene-stimulated latex production in rubber tree seedlings is partly due to the alteration of sucrose metabolism in leaves, and ethylene has an adverse physiological effect on rubber trees.

Hevea brasiliensis Muell. Arg., Enzymes activity, Photosynthesis, Starch, Sucrose.