Effects of elevated CO2 concentration on water use efficiency of Tamarix ramosissima in an extremely arid region

• Published in: Environmental earth sciences 2016-11, Vol.75 (21), p.1, Article 1409
• Main Authors: Chang, Zongqiang, Ma, Yali, Zhou, Chenglin
• Format: Article
• Language: English
• Subjects: Arid zones; Biogeosciences; Carbon dioxide; Earth and Environmental Science; Earth Sciences; Environmental Science and Engineering; Geochemistry; Geology; Growing season; Hydrology/Water Resources; Leaves; Light intensity; Original Article; Photosynthesis; Terrestrial Pollution; Transpiration; Water use; Water use efficiency
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-016-6221-1

The variation of net photosynthetic rate ( P n ), transpiration rate ( T r ), and intercellular CO 2 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 CO 2 concentration, from 17.69 to 27.05 µmol/(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 CO 2 concentration. P n and WUE increased with CO 2 concentration when that concentration was 200–600 µmol/mol. When that concentration increased to 1000 µmol/mol, WUE increased initially but eventually decreased.