Abstract:

The physiological parameters of five species, Yulania biondii (Pamp.) D. L. Fu, Y. liliiflora (Desr.) D. L. Fu,Y. denudata (Desr.) D. L. Fu, Y. axilliflora (T. B. Zhao et al.) D. L. Fu and Y. wugangensis (T. B. Zhao et al.) D. L. Fu were measured. Their light compensation point for photosynthesis was about 10.0 μmol·m^-2s^-1, the photosynthesis saturated PAR was about 1 000 μmol·m^-2s^-1, and the mean photo-respiration rate was 2.1 μmol·m^-2s^-1. The main photosynthetic difference among five species was the light saturated photosynthetic rate (p_max). The value of p_max of 5 species was 8.2 μmol·m^-2s^-1 for Y. biondii, 8.0 μmol·m^-2s^-1 for Y. liliiflora, 14.4 μmol·m^-2s^-1 for Y. denudata, 11 μmol·m^-2s^-1 for Y. axilliflora and 15.3 μmol·m^-2s^-1 for Y. wugangensis. The CO₂ compensation point for leaf photosynthesis was 127 μmol·mol^-1 for Y. biondii, 62 μmol·mol^-1 for Y. liliiflora, 52 μmol·mol^-1 for Y. denudata, 106 μmol·mol^-1 for Y. axilliflora and 51 μmol·mol^-1 for Y. wugangensis.WUE (water use efficiency) was also significantly different, and was 0.14% for Y. biondii, 0.29% for Y. liliiflora, 0.16% for Y. denudata, 0.20% for Y. axilliflora and 0.24% for Y. wugangensis. Y. biondii, the most important species for Xinyi medicine in China, its WUE was the lowest and its CO₂ compensation point was the highest among all five species, therefore it was important to irrigate the plants in the water limited environment and to maintain a relatively sparse canopy in order to increase the bud yield of Xinyi.

Key words: Yulania, Photosynthesis, Water use efficiency, Maximum photosynthetic rate, CO₂ compensation point