Abstract:

Under the field conditions in winter, diurnal variations and light response of photosynthesis in leaves of three cultivated species and their wild species of Ziziphus mauritiana Lam. were investigated by using the Li-6400 portable photosynthesis system. The results indicated that the diurnal variation of net photosynthetic rate (Pn) exhibited dual-peak curves because of midday depression. Pn, transpiration rate (Tr) and water use efficiency (WUE) of Dacuimi cultivar were significantly higher than those of Misi and Wuqian cultivars. The lightly increase in Ci and the decrease in stomatal limitation (Ls) accompanied a reduction of Pn at noon indicated that the depression of photosynthetic rate was mainly due to the non-stomatal limitations. The light compensation point (LCP) and saturation point (LSP) were 21.2～51.6 (mol·m-2·s-1 and 800～1800 (mol·m-2·s-1 ,respectively, in these cultivars, and the apparent quantum yield(AQY) were 0.032～0.057. Thus, it is suggested that the tested four Ziziphus mauritiana Lam. were heliophilous plants. Because of higher LSP in Dacuimi and wild species, these plants showed heliophilous abilities. However, the LSP and LCP of Wuqian were lower than the others, which might reveal a helioskiophyte feature. Therefore, it was suggested that appropriate cultivars and managing methods should be chosen by different photosynthetic traits such as Pn, WUE and Tr in the production of Ziziphus mauritiana Lam.

Key words: Ziziphus mauritiana Lam., photosynthesis, diurnal variations, light response, midday depression