关键词: 半日花, 光合作用, 蒸腾作用, 叶绿素荧光, 环境因子

Abstract: Analysis on a series of physiological and ecological characteristics of photosynthesis of Helianthemum soongoricum during the growth season shows that the daily change pattern of net photosynthetic rate (P_n) of Helianthemum soongoricum can be expressed as a two-peak curve. The P_n reaches the maximum at 9:00 and 15:00. The daily change pattern of transpiration rate (E) is a one-peak curve, and the E value reaches the maximum at 15:00. Analysis also shows that the air temperature (T_a) and the stomatal conductance (g_s) are the two most influential factors on the photosynthesis and transpiration of Helianthemum soongoricum. From the diurnal variation of chlorophyll fluorescence parameter of Helianthemum soongoricum, the intensive light and high temperature have deep effect on the PSⅡ system and make it reversible, appearing the midday depression of photosynthesis.

Key words: Helianthemum soongoricum, photosynthesis, transpiration, chlorophyll fluorescence, environmental factors