Chin J Plan Ecolo ›› 2011, Vol. 35 ›› Issue (2): 176-186.doi: 10.3724/SP.J.1258.2011.00176
• Research Articles •
SHI Sheng-Bo1,2*, SHANG Yan-Xia2, ZHU Peng-Jin2, ZHANG De-Gang1
Aims In the Qinghai-Tibet area, high levels of UV-B radiation reach the earth’s surface as part of strong solar radiation. It is therefore important to examine the response and adaptation of native alpine plants to strong UV-B radiation. Our objective was to determine the physiological response of the photosynthetic apparatus to current ambient UV-B intensity. Methods UV-B-exclusion experiments were conducted on a field site with UV-B-excluding and UV-B-transmitting filters. The two filters transmitted similar levels of photosynthetically active radiation, and there were no differences in air temperature and relative humidity under these metal-frame suspended plastic filters. The experiments were performed in alpine Kobresia humilis meadow with the native alpine species Saussurea superba. Pulse-modulated in vivo chlorophyll fluorescence was mainly used to obtain rapid information on UV-B effects on photosynthetic processes. The trials lasted 15 or 16 days during the growing season of July and August in 2008 and 2009. We measured the 3-min dark-adapted quantum efficiency of PSII photochemistry (F(v)/F(m)), PSII photochemistry efficiency and photosynthetic gas exchange parameters under natural sunlight. The contents of photosynthetic pigments and UV-B-absorbing compounds were analyzed in terms of both leaf area and leaf fresh weight units. Important findings Net photosynthetic rate, significantly increased after removal of UV-B components from natural sunlight. Although there was no significant difference, the F(v)/F(m) was increased in low UV-B treatment compared with the ambient UV-B control. Both the coefficient of photochemical quenching and actual photochemical efficiency of PSII in the light were higher in low UV-B treatment compared to ambient UV-B during the 16 days of continuous measurement during clear days. Variation of PSII maximum efficiency in the light and nonphotochemical quenching further confirmed that the decrease in PSII photochemistry efficiency and increase in nonphotochemical quenching were the results of a strong solar UV-B component in natural sunlight. There was only a slight increase in photosynthetic pigments based both on leaf area and fresh weight after removing UV-B radiation, and these phenomena indicated that strong solar UV-B radiation could photo-oxidize photosynthetic pigments and further accelerate the maturity and senescence of plant cells. UV-B-absorbing compounds were not altered after removal of UV-B radiation, which suggested that high levels of UV-B-absorbing compounds in the epidermal cell layer could protect photosynthetic function from UV-B.
SHI Sheng-Bo, SHANG Yan-Xia, ZHU Peng-Jin, ZHANG De-Gang. Effects of UV-B exclusion on photosynthetic physiology in alpine plant Saussurea superba[J].Chin J Plan Ecolo, 2011, 35(2): 176-186.
Add to citation manager EndNote|Reference Manager|ProCite|BibTeX|RefWorks
Copyright © 2018 Chinese Journal of Plant Ecology
Tel: 010-62836134, 62836138, E-mail: firstname.lastname@example.org, email@example.com