© 2006 Heron Publishing—Victoria, Canada
Growth and physiological responses to supplemental UV-B radiation of two contrasting poplar species
Jian Ren (1, 2, 3), Yinan Yao (1, 2), Yongqing Yang (1, 2), Helena Korpelainen (4), Olavi Junttila (5) and Chunyang Li (1, 6)
1. Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu 610041, P.R. China / 2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, P.R. China / 3. Department of Grassland Sciences, Yunnan Agricultural University, Kunming 650201, P.R. China / 4. Department of Applied Biology, P.O. Box 27, FI-00014 University of Helsinki, Finland / 5. Department of Biology, University of Tromsö, N-9037 Tromsö, Norway / 6. Corresponding author (licy@cib.ac.cn) / Received May 9, 2005; accepted July 28, 2005; published online February 1, 2006
Summary
We compared the growth and physiological responses of cuttings of Populus kangdingensis C. Wang et Tung and P. cathayana Rehder originating from altitudes of 3500 m and 1500 m, respectively, when exposed to three ultraviolet-B (UV-B) radiation
regimes: zero UV-B, ambient (4.5 kJ m–2 day–1) and twice-ambient (9 kJ m–2 day–1) biologically effective UV-B radiation for one growing season, to determine if Populus trees that are adapted to contrasting UV-B habitats exhibit different tolerances to enhanced UV-B radiation. Compared with
cuttings grown without UV-B radiation, twice-ambient UV-B radiation significantly decreased total biomass, total leaf area
and internode length in both species, whereas root/shoot ratio, leaf number, amount of photosynthetic pigments and ascorbate
peroxidase activity were unaffected. Differences in responses were also observed between the study species. Cutting height
increment, total biomass, total leaf area, free proline concentration and membrane damage assessed by electrolyte leakage
were significantly more affected by the twice-ambient UV-B radiation in P. cathayana than in P. kangdingensis. However, specific leaf mass, amount of UV-B absorbing compounds and superoxide dismutase and guaiacol peroxidase activities
increased more with increasing UV-B radiation in P. kangdingensis than in P. cathayana, perhaps reflecting important characteristics of species with low to moderate tolerance to UV-B radiation. Overall, the results
indicated that P. kangdingensis, which originates from altitudes of 3500 m, has greater tolerance to enhanced UV-B radiation than P. cathayana originating from altitudes of 1500 m.
Keywords:
antioxidant enzymes, electrolyte leakage, free proline, UV-B absorbing compounds.
