Abstract: Sinojackia huangmeiensis, an endemic species with extremely small population in China, was listed as one of the national key protected wild plants. To investigate the response and acclimation of S. huangmeiensis to different light environments, we selected plants in three habitats (gap, understory, and full sunlight habitats), and compared leaf phenotypic traits, photosynthetic characteristics and chlorophyll fluorescence parameters in different habitats. Compared to the full sunlight habitat, specific leaf area (SLA) of S. huangmeiensis was significantly higher, while leaf thickness (LT) and dry matter content (LDMC) were significantly lower in gap and understory habitats. The maximum net photosynthetic rate (P_max) and light saturation point (LSP) were the highest in the full sunlight habitat, while light compensation point (LCP) and dark respiration rate (R_d) were the lowest in the understory habitat. The electron transport rate (ETR), the effective PSⅡ quantum yield \[Y(II)\], photochemical quenching (qP) and non-photochemical quenching (NPQ) in gap and full sunlight habitats were higher than those in the understory habitat. Our results suggested that S. huangmeiensis can acclimate to the low light environment by reducing LCP, R_d and NPQ, and acclimate to the high light environment by increasing LT, LDMC, LSP and NPQ. Additionally, S. huangmeiensis showed strong acclimation to different habitats, which was of great importance for population regeneration and maintenance, and thus provided new insights for artificial introduction.

Key words: endangered plant species, leaf phenotypic trait, photosynthesis, chlorophyll fluorescence