Chin J Plant Ecol ›› 2007, Vol. 31 ›› Issue (3): 490-496.DOI: 10.17521/cjpe.2007.0061

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XIAO Yue-E1, CHEN Kai-Ning2, DAI Xin-Bin1, XU Xiao-Ming1,*()   

  1. 1Department of Plant Sciences, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
    2Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, Nanjing 210008, China
  • Received:2006-03-24 Accepted:2006-07-31 Online:2007-03-24 Published:2007-05-30
  • Contact: XU Xiao-Ming


Aims The difference in efficiency and mechanism of absorption of dissolved inorganic carbon (DIC) by two common species in Taihu Lake, Potamogeton crispus and P. malaianus, has rarely been studied. We ask: 1) do the two species differ in DIC absorption efficiency, and 2) what are the implications of any difference, especially in terms of succession in summer?
Methods We used a pH drift experiment to assess abilities of the two species to use DIC. Matching the natural inorganic carbon in Taihu Lake, we used three different alkalinities (1 200, 1 600, and 2 000 μmol·L-1), pH values and ${HCO_{3}}^{-}$ concentrations at the beginning of the experiments. Simultaneously, we measured the activity of carbonic anhydrase of both species.
Important findings Both species can utilize ${HCO_{3}}^{-}$ and adapt to low inorganic carbon conditions. Both species used ${HCO_{3}}^{-}$ more efficiently at high alkalinity, so the efficiency of ${HCO_{3}}^{-}$ use depends on the concentration of this ion. However, different efficiencies in the use of ${HCO_{3}}^{-}$ were evident in terms of the photosynthetic rates and pH values attained at the end of the experiments. Photosynthesis rates and pH values of P. malaianus were higher than those of P. crispus at all alkalinities. Photosynthetic rates-CO2 curves of the two species showed that P. malaianus uses CO2 more efficiently than P. crispus when the pH value of water is higher, i.e., when the concentration of CO2 is low. Furthermore, the carbonic anhydrase activity of P. malaianus was distinctly higher than that of P. crispus. This result showed P. malaianus could transfer ${HCO_{3}}^{-}$ to CO2 more quickly than P. crispus, which was correlated with the different efficiencies of use of inorganic carbon. This study suggests the pH of Taihu Lake in summer may be advantageous to the colonization of P. malaianus, compared to P. crispus. Furthermore, the different efficiencies correlate with the successional patterns of the two submerged macrophytes.

Key words: submerged macrophyte, dissolved inorganic carbon, photosynthetic rate, carbonic anhydrase, population succession