Chin J Plan Ecolo ›› 2012, Vol. 36 ›› Issue (5): 420-430.DOI: 10.3724/SP.J.1258.2012.00420

• Research Articles • Previous Articles     Next Articles

Responses of PSII photochemistry efficiency and photosynthetic pigments of Saussurea superba to short-term UV-B-supplementation

SHI Sheng-Bo1*, SHANG Yan-Xia1,2, SHI Rui3, and ZHANG Bo1,2   

  1. 1Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Plateau Institute of Biology, Chinese Academy of Sciences, Xining 810001, China;

    2Graduate University of Chinese Academy of Sciences, Beijing 100049, China;

    3School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
  • Received:2011-11-28 Revised:2012-03-15 Online:2012-05-01 Published:2012-05-04
  • Contact: SHI Sheng-Bo

Abstract:

Aims Native alpine plants that have grown and evolved on the Qinghai-Tibetan Plateau of China for a long time have developed a strong adaptation capacity for harsh environmental factors, such as low temperature, low air pressure, strong sunlight and solar UV-B radiation. The objective of this study was to determine the response of PSII photochemistry efficiency to short-term enhanced solar UV-B intensity in alpine plants. We examined whether UV-B-absorbing compounds were sufficiently efficient to protect the photosynthetic apparatus from UV-B photo-inactivation or photo-damage and evaluated the influence of UV-B radiation on photosynthetic pigments.
Methods Field experiments were conducted during the 2008 and 2009 growing seasons in alpine Kobresia humilis meadow near Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′ N, 101°12′–101°33′ E; alt. 3 200 m) using the native alpine plant Saussurea superba. Short-term UV-B-supplementation studies were performed over 5 days using UV-B-313 fluorescence lamps, which were filtered with a cellulose diacetate film to get increased UV-B treatment and a Mylar film as a control. Pulse-modulated in-vivo chlorophyll fluorescence was used to obtain rapid information of UV-B on photosynthetic processes. The 3-min dark-adapted maximum quantum efficiency of PSII photochemistry, F(v)/F(m), and PSII photochemistry efficiency were measured under natural sunlight. The contents of photosynthetic pigments and UV-B-absorbing compounds were analyzed based on leaf area unit.
Important findings Although there was no significant difference, F(v)/F(m) showed a decreasing trend after short-term exposure to enhanced UV-B radiation in all measurements throughout the growing season. The reduction of the actual photochemical quantum efficiency and photochemical quenching as well as the increase of non-photochemical quenching in UV-B supplemented treatment, when compared to the control, indicated there was a decrease in PSII photochemistry efficiency and an increase in non-photochemical quenching. These phenomena indicated photo-inactivation or photo-damage of photosynthesis occurred in the PSII reaction center. The photosynthetic pigments showed a small decrease in the UV-B supplemented treatment, which may be related to the enhancement of photo-oxidation, a reduction of pigment synthesis and small variation of leaf thickness. The UV-B-absorbing compounds were not influenced by short-term enhancement of UV-B radiation when analyzed based on leaf area unit. This demonstrated that higher contents of UV-B-absorbing compounds in the epidermal layer of alpine plant S. superba were efficient for defense against UV-B radiation and stabilized for further enhancement of UV-B radiation