Chin J Plant Ecol ›› 2011, Vol. 35 ›› Issue (7): 741-750.DOI: 10.3724/SP.J.1258.2011.00741

Special Issue: 青藏高原植物生态学:生理生态学

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Effects of solar UV-B radiation on the efficiency of PSII photochemistry in the alpine plant Saussurea superba under different weather conditions in the Qinghai-Tibet Plateau of China

SHI Sheng-Bo1,*(), SHANG Yan-Xia1,2, ZHU Peng-Jin1,2, YANG Li1,2, ZHANG Bo1,3   

  1. 1Key Laboratory of Adaptation and Evolution of Plateau Biology, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810001, China
    2Graduate University of Chinese Academy of Sciences, Beijing 100049, China
    3The Lanzhou Branch of the National Science Library, the Scientific Information Center for Resources and Environment, Chinese Academy of Sciences, Lanzhou 730000, China
  • Published:2011-08-18
  • Contact: SHI Sheng-Bo


Aims Strong solar UV-B radiation accompanied with strong solar visible radiation is a characteristic of the environment of China’s Qinghai-Tibet Plateau. Previous study confirmed that current ambient UV-B intensity has a small negative influence on the physiological response of the photosynthetic apparatus of the alpine plant Saussurea superba. Our objectives were to further analysis the influence of ambient UV-B intensity on PSII photochemistry efficiency under different weather conditions.
Methods Short-term field experiments of UV-B were conducted during the luxuriant growing season in Kobresia humilis meadow in the Haibei Alpine Meadow Ecosystem Research Station. We used the pulse-modulated in vivo chlorophyll fluorescence technique to obtain rapid information on the effects of UV-B intensities on photosynthetic performances in the native alpine plant S. superba. The maximum quantum efficiency of PSII photochemistry (F(v)/F(m)) was measured after 3 minutes of dark radiation. The PSII photochemistry efficiency and non-photochemical quenching parameters were also measured. All chlorophyll fluorescence parameters were statistically analyzed with SPSS 11.0 software according to sunny, cloudy and shady weather states. Two-way ANOVA and least significant difference method (LSD) were used to compare differences among UV-B treatments and weather states.
Important findings There were significant increases of F(v)/F(m) in both ambient UV-B and low UV-B treatments when the weather changed from clear days to overcast days. Although there were no significant differences, F(v)/F(m) showed an increased trend in low UV-B when compared with ambient UV-B in all three weather states. This suggests that ambient UV-B intensity can delay the recovery of optimal photochemistry efficiency in S. superba. There were (a) increased tendency in actual photochemical efficiency of PSII (ΦPSII) and photochemical quenching (qP) and (b) small decreased tendency in non-photochemical quenching (NPQ) in low UV-B treatment in comparison with ambient UV-B; however, all those fluorescence parameters were significantly changed among the three weather states. The variation of these PSII photochemistry efficiency parameters demonstrated that natural UV-B component can limit the photosynthetic performance. Further analysis confirmed that significant difference (p < 0.05 on sunny days and p < 0.01 on shady days) existed in relative limitation of quantum efficiency (L(PFD)) and fraction of opened PSII centers (qL). Although its effects were not always significant when compared with the influence of photosynthetically active radiation (PAR), UV-B radiation can influence primary quinine electron acceptor of PSII (QA) and there were negative effects on photosynthetic organization in S. superba.

Key words: alpine plant, chlorophyll fluorescence, PSII photochemical efficiency, Qinghai-Tibet plateau, UV-B radiation, weather state