Abstract: To explore the photosynthetic physiological responses of Phoebe bournei (Hemsley) Yang to different light regimes, we measured several parameters, including chlorophyll contents, chlorophyll fluorescence parameters, intrinsic characteristics of light-harvesting pigment molecules, and energy partitioning. The results showed that the contents of chlorophyll a, chlorophyll b and carotenoids for one and three-year-old P. bournei seedlings grown under 88.3% shading were significantly higher than those under full light. Shading treatment increased minimal fluorescence (F_o), maximal photochemical efficiency of PSII in the dark (F_v/F_m), and photochemical efficiency of PSII in the light (F_v′/F_m′), but decreased photochemical quenching (q_P) and nonphotochemical quenching (NPQ) of leaves. Seedlings grown under 88.3% shading had higher values of effective light absorption cross-section of light-harvesting pigment molecules (σ_ik′) and thermal energy dissipation (D), but lower values of light-harvesting pigment molecules in the lowest excited state (N_k) and non-photochemical energy dissipation (E) compared with those grown under full light. There was no significant difference between one-year-old and three-year-old seedlings for chlorophyll contents, carotenoids contents, F_v/F_m,F_v′/F_m′, and NPQunder all treatments. However, one-year-old seedlings had lower q_P, electron transport rate (ETR), σ_ik′, and photochemical reaction (P), and higher N_k and Ethan three-year-old seedlings grown under full light. The results suggest that one and three-year-old P. bournei seedlings can grow well under shading, whereas photoinhibition occurs under full light. Three-year-old P. bournei had higher tolerance to high-light stress than one-year-old seedlings.

Key words: Phoebe bournei, simulated light condition, chlorophyll content, chlorophyll fluorescence, light adaptation.