干旱区生态环境知识资源中心

The variation of net photosynthetic rate (P-n), transpiration rate (T-r), and intercellular CO2 concentration (Ci) with changes in light intensity of Tamarix ramosissima leaves was studied during the growing seasons of 2012 and 2013 in the extremely arid region of Ejina Oasis, using the LI-6400 portable photosynthesis measurement system. Results indicate that Ci decreased and P-n and T-r increased with light intensity. After reaching the light saturation point, P-n decreased gradually with the enhanced greater light intensity. The apparent maximum photosynthetic rate increased with CO2 concentration, from 17.69 to 27.05 mu mol/(m(2) s); apparent quantum efficiency also increased, as did the light saturation point of T. ramosissima leaves. Water use efficiency (WUE) increased initially but gradually decreased after maximizing with the enhanced light intensity. T-r and Ci increased with elevated CO2 concentration. P-n and WUE increased with CO2 concentration when that concentration was 200-600 mu mol/mol. When that concentration increased to 1000 mu mol/mol, WUE increased initially but eventually decreased.