Abstract:Taking naturally distributed Dinochloa orenuda (strong climbing ability) and Bonia levigata (weak climbing ability) in Ganshenling, Hainan Island as the experimental materials, we investigated light response curve and the CO2 response curve of leaves in February, April, July and November to analyze photosynthetic characteristics of climbing bamboo and their adaptation mechanisms to rainforests by using Li6400 portable photosynthesis system. Results showed that: (1) compared to B. levigata, D. orenuda generally had higher lightsaturated maximum net photosynthetic rate (Pnlmax), light saturation point (LSP), light compensation point (LCP), dark respiration efficiency (Rd) and stomatal conductance (Cond), but showed lower apparent quantum efficiency (AQE) and intercellular carbon dioxide concentration (Ci) determined in each month. (2)The Pnlmax, LSP, LCP, Rd, Cond, Ci and Tr of the two bamboo species determined in July were higher than those determined in other months, and the AQE and water use efficiency (WUE) determined in February were higher than those determined in other months. (3) The carboxylation efficiency (CE), CO2saturated net photosynthetic rate (Pncmax) and photorespiration rate (Rp) determined in each month of D. orenuda were higher than those of B. levigate. For the two bamboo species, the CO2 saturation point and CO2 compensation point determined in April were higher than those determined in other months, but their CE and Pncmax were lower. In general, D. orenuda was a lightloving plant which had stronger photosynthetic capacity and adaptive capacity to CO2 concentration changed, while B. levigata coexisted with other species in tropical rain forests due to its shadetolerant properties. The two bamboos both generally had stronger photosynthetic capacity during the rainy season than during the dry season. In the rainy season. two bamboos mainly increased their net photosynthetic rate by increasing LSP, Cond, and Ci, and during the dry season, photosynthesis was mainly maintained by reducing Tr and increasing WUE. Overall, Seasonal changes in photosynthetic characteristics of two bamboos were the result of the combined action of the environment and the physiological characteristics of the species. The two bamboos grown in the rainforest developed different survival strategies due to their different photosynthetic characteristics.