The Partition For Leaf Nitrogen In Photosynthetic Of The Five Indigenous Tree Species

In order to better understand the partition of leaf nitrogen in photosynthetic and its responses feature with environmental variation of indigenous tree species. Five indigenous tree species seedlings (Cinnamomum longepaniculatum, Sassafras tzumu, Toona ciliata, Cyclobalanopsis glauca and Sapium sebiferum.) were selected to study the light response curve, carbon dioxide response curve, specific leaf area, leaf chlorophyll concentration, leaf nitrogen content, leaf phosphorus content, and the partition coefficient of leaf nitrogen allocation in photosynthetic machinery was also calculated. We analyzed the allocation feature of leaf nitrogen in photosynthetic of the five indigenous tree species seedlings. Meanwhile, the photosynthetic characteristics, leaf nitrogen content and the partition coefficient of leaf nitrogen allocation in photosynthetic machinery of C. longepaniculatum which planted in seven different size gaps (T1:10 m×10 m, T2:15 m×15 m, T3:20 m×20 m, T4:25 m×25 m, T5:30 m×30 m, T6:35 m×35 m and T7:40 m×40 m) of Pinus massoniana plantation and open land(CK)were observed comparatively. The main results are as follows:(1) The maximum net photosynthetic rate and the minimum nitrogen content were observed in C. longepaniculatum, the high PT among the five indigenous tree species seedlings. PL and PT are great decision factors to Pmax, S. tzumu have the minimum net photosynthetic rate but a high PT, which was higher than the other four indigenous tree species seedlings in PL. The leaf nitrogen content of S. sebiferum seedling was significantly higher than the other four species and the phosphorus content was significantly lower than the other four species, which was lowest among the other four species in PT. Nitrogen allocation pattern is not the same in the five indigenous tree species seedlings, the difference in nitrogen allocation pattern may indicate differences in the ability of species to adapt to the environment.(2) Study the partition of leaf nitrogen in photosynthetic of C. longepaniculatum in different P. massoniana forest gaps, the results follow, when the size of forest gaps was less than 20 m × 20 m, the maximum net photosynthetic rate of the leaves of C. longepaniculatum seedlings was significantly lower than that in open land. With an increase of forest gap size, leaf mass per unit area increased significantly. Compared with the control, although the leaf nitrogen content of C. longepaniculatum seedlings decreased significantly in small forest gaps (e.g.,10 m × 10 m), it increased significantly in large gaps (e.g.,20 m×20 m). Nevertheless, no significant difference was observed in the phosphorus content of leaves of seedlings grown in either forest gaps or in open land. With an increase in forest gap size, total partition coefficients of leaf nitrogen in the photosynthetic apparatus increased, especially the partition coefficients of leaf nitrogen in carboxylation components. Nevertheless, the coefficient of leaf nitrogen partitioning into the light harvesting apparatus decreased significantly with an increase in the size of forest gaps (10 m×10 m-20 m×20 m). The results demonstrated that if the gap size is less than 20 m×20 m forest gaps have marked effects on the photosynthetic capacity of C. longepaniculatum seedlings. Seedlings may adapt to changes in the forest gap environment by adjusting a number of morphological and physiological characteristics, e.g., specific leaf area, leaf nitrogen content and the distribution of leaf nitrogen in the photosynthetic apparatus.