Chinese Bulletin of Botany ›› 2011, Vol. 46 ›› Issue (4): 413-424.DOI: 10.3724/SP.J.1259.2011.00413

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Effect of Drought Stress on Photochemical Efficiency and Dissipation of Excited Energy in Photosystem II of Populus euphratica

Chenggang Zhu1,2, Yaning Chen1*, Weihong Li1, Aihong Fu1, Yuhai Yang1   

  1. 1State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy ofSciences, Urumqi 830011, China;

    2 Graduate University, Chinese Academy of Sciences, Beijing 100049, China
  • Received:2010-11-18 Revised:2011-03-03 Online:2011-07-01 Published:2011-07-01
  • Contact: Yaning Chen

Abstract: We selected 4 survey plots with groundwater depths > 4 m near ecological monitoring wells in the Tarim River to investigate leaf water potential, leaf relative water content, and chlorophyll fluorescence characteristics of Populus euphratica under drought stress induced by decreased groundwater level. We analyzed the impact of drought stress on photosystem II photochemical efficiency and excited energy dissipation in terms of energy metabolism and conversion. The leaf water potential of P. euphratica significantly decreased with increasing drought stress induced by increasing groundwater depth, with no significant differences in leaf relative water content, which maintained optimal values (80.38%–86.19%). Under drought stress, synthetically photosynthetic activity and the leaf light saturation point of P. euphratica significantly decreased, and photosynthetic electron transportation rate, actual photochemical efficiency of photosystem II in the light and photochemical quenching of P. euphratica decreased with increasing photosynthetic active radiation. Greater decreases occurred with more severe drought stress. The non-photochemical quenching and the yield for dissipation by downregulation of P. euphratica under drought stress significantly increased with increasing photosynthetic active radiation, and the maximal photochemical efficiency was maintained at an optimal value (0.80–0.86). Increasing drought stress would result in significantly decreased share of photosynthetic solar energy utilization, whereas the ability to withstand high light intensity decreased, which would result in greater excess of excited energy. P. euphratica can release the stress resulting from excess excited energy by heat dissipation, which plays an important role in the process of energy metabolism on the photosystem of P. euphratica. Although the photosystem II of P. euphratica under drought stress in the lower reaches of the Tarim River has not yet been irreversibly damaged because of light inhibition, the potential crisis of light injury induced by light inhibition is increasing.