Photosynthesis and transpiration are the most important physiological activities for plants. They are closely related not only to photosynthesis active radiation (PAR), air temperature (Ta), relative humility (RH) and ambient CO2 concentration, but also to plant stomatal conductance and intercellular CO2 concentration. Their relationship can be analyzed through statistic methods to indicate plant eco-physiological ability bearing to environment. By means of measuring the photosynthesis of Haloxylon ammodendron and Reaumuria soongorica in the Sangonghe River valley we have dealt with similarities and differences of two species. Results show that net photosynthesis rate of Reaumuria soongorica is slight higher than Haloxylon ammodendron, but water use efficiency of Haloxylon ammodendron is evidently higher than Reaumuria soongorica. It suggests that Haloxylon ammodendron has strong bearing ability to drought in natural habitat.
Leaf stomata play a very important roll in plant physiological activities and the interaction between plant and atmosphere. In one hand, plants get CO2 for photosynthesis through stomata. In the other hand, stomata control the water losses causing by transpiration. So that, stomata is not only the key element controlling transpiration and latent heat flux, but also the key factor for photosynthesis. Evidences indicate that besides plant physiological traits, stomatal conductance is very sensitive to environmental elements such as photosynthesis active radiation (PAR), relative humility (RH), air temperature (Ta), leaf temperature (Tl), ambient CO2 concentration etc.