太湖两种大型沉水植物无机碳利用效率差异及其机理

doi:10.17521/cjpe.2007.0061

摘要/Abstract

摘要：

该文通过pH值漂移实验比较了太湖常见的两种沉水植物菹草(Potamogeton crispus)和马来眼子菜(P. malaianus)对无机碳利用效率的差异,并测定两者无机碳吸收关键酶——碳酸酐酶的活性,探讨了两者无机碳吸收效率差异的原因。根据太湖自然水体的无机碳条件设定了3种不同碱度条件,测定起点pH值和无机碳条件。不同碱度下pH值漂移变化和总无机碳/碱度比值的结果表明,两个种均能利用${HCO_{3}}^{-}$,适应低无机碳条件。两者对${HCO_{3}}^{-}$的吸收速率决定于其浓度大小,该离子浓度越大,光合速率越高。但是对${HCO_{3}}^{-}$的吸收速率存在差异:马来眼子菜在各碱度下终点pH值显著高于菹草,整体光合速率较高。CO₂-光合速率响应曲线表明,在高pH值(CO₂受到限制)时,马来眼子菜对CO₂亲和力较大。尽管菹草在pH值较低(6.5~7.0)时有相对较高的光合速率,但是基于太湖自然水体夏季高pH值(>8.5)条件,马来眼子菜具有更大的生长优势,成为优势种群。两者无机碳吸收速率的差异是造成它们生活史差异和时间生态位的一重要原因。同时,马来眼子菜碳酸酐酶活性明显高于菹草,表明在相同无机碳条件下,前者催化${HCO_{3}}^{-}$与CO₂之间的转化效率更高,这可能是造成两者无机碳吸收速率差异的原因。

关键词: 沉水植物, 无机碳, 光合速率, 碳酸酐酶, 种群演替

Abstract:

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

肖月娥, 陈开宁, 戴新宾, 许晓明. 太湖两种大型沉水植物无机碳利用效率差异及其机理. 植物生态学报, 2007, 31(3): 490-496. DOI: 10.17521/cjpe.2007.0061

XIAO Yue-E, CHEN Kai-Ning, DAI Xin-Bin, XU Xiao-Ming. DISSOLVED INORGANIC CARBON UPTAKE IN TWO SUBMERGED MACROPHYTES FROM TAIHU LAKE, CHINA. Chinese Journal of Plant Ecology, 2007, 31(3): 490-496. DOI: 10.17521/cjpe.2007.0061

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2007.0061

https://www.plant-ecology.com/CN/Y2007/V31/I3/490

图/表 5

表1 两种沉水植物在不同碱度条件下终点[CT]、pH值、[CO2]以及[CT]/Alk比值

Table 1 The pH values, [CO2], [CT] and [CT]/Alk quotients reached in pH drift experiments in two submerged macropytes at three alkalinity

	碱度 Alkalinity (μmol·L^-1)	[C_T] (mmol·L^-1)	[CO₂] (μmol·L^-1)	终点pH值 pH values	[C_T]/Alk
马来眼子菜 Potamogeton malaianus	1 200	0.832±0.008	0.079±0.003	10.07±0.01	0.693±0.048^*
	1 600	0.933±0.005	0.085±0.006	10.15±0.05^*	0.583±0.032^*
	2 000	0.906±0.006	0.066±0.003	10.22±0.03^*	0.453±0.026
菹草 P. malaianus	1 200	0.935±0.007	0.210±0.071^*	9.86±0.03	0.779±0.034
	1 600	0.983±0.005^*	0.127±0.005	9.93±0.02	0.614±0.005
	2 000	0.938±0.007^*	0.119±0.065	10.02±0.04	0.469±0.025

图1 不同碱度条件下两种沉水植物pH值-光合速率响应曲线实线和虚线分别代表马来眼子菜和菹草的光合速率响应曲线,右上角的各小图为pH值为8.0~10.5的放大图

Fig.1 Photosynthetic rates-pH curves of two submerged macrophytes in three different alkalinities Real lines and dotted lines indicated photosynthetic rates-pH curve of Potamogeton malaianus and P. cripus respectively, and above right figures are all enlarged when pH values were from 8.0 to 10.5

图2 两种沉水植物在不同碱度下的光合速率变化趋势比较

Fig.2 Photosynthetic rates of two submerged macrophytes at different alkalinities

图3 两种沉水植物的CO2-光合速率响应比较右图为CO2低于200 μmol·L-1时的光合速率响应曲线,R2(马来眼子菜)=0.928,R2(菹草)=0.899

Fig.3 Photosynthetic rates-CO2 curves of two submerged macrophytes Right figure indicated the photosynthetic rates-CO2 curve when the concentration CO2 were lower than 200 μmol·L-1 with R2 (Potamogeton malaianus)=0.928 and R2 (P. cripus)=0.899

图4 两种沉水植物碳酸酐酶活性比较

Fig.4 Comparison the activity of Carbonic Anhydrase in two submerged macrophytes

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