Study Of Photosynthetic Characteristics On Seedlings Of Tsoongiodendron Odorum And Phoebe Bournei

Both Tsoongiodendron odorum and Phoebe bournei have a good economic value. Due to over-harvesting and habitat destruction, T. odrum and P. bournei nearly depleted natural resources, so it is as a national rare and endangered plants. There is focus on the reasons for these two endangered species and how the issue of protection in recent years. Therefore, it is especially important to study these two species physiological response to different light environments in theotetical and practical level. We choose three years old saplings of T. odrum and P. bournei in WanMuLin Nature Reserve, Fujian Province. The treatment of Light availabilities included three levels,100%, 40% and 8% of full light. The photosynthesis-related parameters under three light environments in four seasons were measured by the technique of gas exchange and chlorophyll fluorescence.The results show that:1. The low light environment (8% light environmnet),the light saturation point (LSP), light compensation point (LCP), dark respiration (Rd), photorespiration (Rp) and the CO2 compensation point (Γ) of these two species were significantly lower than full sunlight (p<0.05). The apparent quantum efficiency (AQY) and chlorophyll a/b were significantly higher than the value of the full light (p<0.05). Low light environment of two speices of non-photochemical quenching (qN) and specific leaf weight (LMA) were significantly lowest (p<0.05)2. Under the middle light environment (40% of the light environment) of these two species, the highest Pnmax, LSP, and carboxylation efficiency (CE). At the maximum photochemical efficiency (Fv/Fm) highest, and the Fv/Fm and photochemical quenching (qP) of the diurnal variation of the value of higher chlorophyll content and leaf nitrogen content is highest.3. With reduced light environment, Pnmax and CE of P. bournei saplings gradually decreased, Fv/Fm and qP were daily changes gradually diminished, and the P. bournei saplings in full light has the highest total chlorophyll content and leaf nitrogen content.4. The winter is the end of the growing season about two kinds of speices, full light environment of T. odrum and P. bournei of Pnmax, AQY, CE, qP, chlorophyll content were lower than the value of the two shade environments, compared to other seasons. In winter, two kinds of species under full sunlight in photosynthetic capacity would drop,in particular the P. bournei saplings. Two kinds of speices in the winter morning Fv/Fm were lowest, and less than 0.75. Two kinds of speices under the 40% of the light conditions of Pnmax, AQY, CE, qP decreased in than other seasons, but the drop rate of decline less than in full sunlight, and the Fv/Fm were highest in three light environment.This study shows, T. odrum and P. bournei saplings can adapt to low light conditions, but in low-light environment, two kinds of photosynthetic capacity and growth rate were lowest. T. odrum saplings in middle light conditions have the highest growth rate and photosynthetic capacity, while P. bournei saplings suitable to growth in high-light environment. Two kinds of speices in full light in winter would subject to light stress; a certain degree of shade can alleviate the winter light stress.