Abstract:

Photosynthesis and transpiration of Artemisia sacrorum were studied using the Li-6400 portable photosynthesis system in Loess Plateau region．The results showed that the diumal variation of net photosynthetic rate (P_n)in A．Sacrorum was single-peak curves from June to September．The diurnal variation of P_n was a bimodal curve and photosynthesis got into middaydepression at 14：00 in May．The light compensation point (LCP) and the light saturation point (LSP) of A．Sacrorum were 44.1 μmol·m^-2s^-1 and 351 μmol·m^-2s^-1．Respectively．The LCP was higher than that of typical sun plants and the LSPverged on that of typical sun plants．This indicated that A．Sacrorum was a sunny and typical sun plant．With PAR increasing，Tr was increasing along and had no saturation peak．When PAR was less than 160 μmol·m^-2s^-1，the water use efficiency (WUE) of A．Sacrorum increased greatly．When PAR variedfrom 160 to 2000μmol·m^-2s^-1，WUE changed from 2.5 to 3.39μmol C0₂·mmol^-1H₂O．It was proved again that A．Sacrorum was a sunny plant．

Key words: Artemisia sacrorum, Loess hilly region, net photosynthetic rate, water use efficiency, photosynthesis-light response