Abstract: Controlled experiment of Leymus chinensis seedlings grown in the
environmental growth chambers at 3 soilmoisture levels and 3 temperature levels
was conducted in order to improve the understanding how leafphotosynthetic
parameters will respond to climatic change. The results indicated that soil
drought and hightemperature decreased the photochemical efficiency of
photosystem (F_v/F_m), the overall
photochemical quantumyield of PSIl (yield), the coefficient of photochemical
fluorescence quenching (q_p), but increased the coefficient
ofnon-photochemical fluorescence quenching (q_N). Severe
soil drought would decrease F_v/F_m and
yield by 3.12% and 37.04% under 26°C condition, respectively, and
6.60% and 73.33% under 32°C condition, respectively, suggesting
that higher temperature may enhance the negative effects of soil drought. All
the soil drought treatments resulted in the decline in leaf nitrogen content.
There was no significant effect of temperature on leaf nitrogen level, but
higher temperature significantly reduced the root nitrogen content and the
ratio of root nitrogen to leaf nitrogen, indicating the different strategies of
adaptation to soil drought and temperature. It was also implied that higher
temperature would enhance the effect of soil drought on leaf photosynthetic
capacity, decrease the adaptability of Leymus chinensis to drought.
