Chin J Plan Ecolo ›› 2011, Vol. 35 ›› Issue (3): 311-321.DOI: 10.3724/SP.J.1258.2011.00311

• Research Articles • Previous Articles     Next Articles

Photosynthetic characteristics of Stipa purpurea under irrigation in northern Tibet and its short-term response to temperature and CO2 concentration

GUO Ya-Qi1,2, BORJIGIDAI Almaz3,4, GAO Qing-Zhu1,2*, DUAN Min-Jie1,2, GANZHU Zhabu1,2, WAN Yun-Fan1,2, LI Yu-E1,2, GUO Hong-Bao5   

  1. 1Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China;

    2Key Laboratory forAgro-Environment & Climate Change of Ministry of Agriculture, Beijing 100081, China;

    3China Minority Traditional Medical Center, Minzu University of China, Beijing 100081, China;

    4Key Laboratory for Chinese Minority Traditional Medical of Ministry of Education, Beijing 100081, China;

    5Nagqu PrefectureGrassland Station, Tibet Autonomous Region, Nagqu, Tibet 852100, China
  • Received:2010-10-26 Revised:2011-01-22 Online:2011-03-01 Published:2011-03-02
  • Contact: GAO Qing-Zhu

Abstract:

Aims Stipa purpurea is a dominant species of alpine grassland in northern Tibet, a region sensitive to climate change. Environmental variations in temperature, water and atmospheric carbon dioxide (CO2) concentration caused by regional climate change should affect the photosynthetic physiology of plants. Our objective was to investigate the response of S. purpurea to environmental variation. Methods We irrigated natural alpine grassland to imitate rainfall increasing soil moisture and then used a portable gas exchange system (LI-6400) to measure photosynthesis parameters at the irrigated field (H) and a natural field (CK). During measurement, we set three levels of leaf temperature (15, 20 and 25 °C) and gradually elevated CO2 concentration from 50 to 1 500 μmol·mol–1. Important findings CO2, temperature and soil moisture affected photosynthesis parameters of S. purpurea significantly, and interactions were apparent among these three factors. Rising CO2 gradually increased net photosynthetic rate (Pn) until it decreased at extremely high CO2. Higher temperature caused Pn to decrease, but sufficient water supply partially alleviated the negative effect. Sufficient water supply increased Pn. With rising CO2, intercellular CO2 concentration (Ci) increased, transpiration rate (Tr) decreased, water use efficiency (WUE) increased and stomatal conductance (Gs) decreased; higher temperature caused Gs to decrease faster. The photosynthesis parameters above were also impacted by the combined actions of humidity and temperature. Gs was maximized at 20 °C, and sufficient water supply increased Gs further. Ci increased with increased temperature, and this response was more pronounced with sufficient water. Tr was positively correlated with temperature and soil water. Vapor pressure deficit (VPD) was directly proportional to temperature and decreased with sufficient water. Increased temperature and increased water supply made WUE decline. Therefore, increased soil water had compensatory effects on the relationship between high temperature and photosynthetic parameters.