Abstract:

Net photosynthetic rates(P_n) were measured in 18month old seedlings of Machilus pauhoi from two provenances of Suichuan in Jiangxi and Jian'ou in Fujian using a LiCor LI6400 portable photosynthesis system(LiCor Inc., Lincoln, NE, USA) with a LED light source. The other photosynthetic parameters, including maximum net photosynthetic rate(P_max), apparent quantum yield(AQY), light saturation point(LSP) and light compensation point(LCP), were also detected in response to irradiation. The results showed: The average P_max, AQY, LSP and LCP of the seedlings from the two provinces were 12.65 μmolCO2·m^-2s^-1, 0.052 7 μmolCO2·μmol^-1 photons, 1.12099 μmol·m^-2 s^-1 and 1803 μmol·m^-2s^-1 respectively. There were significant differences between the two provenances in the all photosynthetic parameters except for AQY. The provenance of Suichuan performed better than that from Jianou with higher P_max，AQY and LSP of 30.48%，4.66% and 25.70% respectively, though the LCP of Suichuan provenance was higher and needed stronger illumination. There was more variation in P_max, AQY, LSP and LCP between the two provenances than that within the two provenances. There were significant differences between the upper and lower crown layers with higher P_max and AQY in the upper crown, while there was no difference in LCP and LSP between the two crown layers due to the integrated influence of the shape of seedling crowns and the photosensitivity of leaves. 

Key words: light response, maximum net photosynthetic rate(P_max), apparent quantum yield(AQY), light saturation point（LSP）, light compensation point（LCP）, Machilus pauhoi