植物生态学报 ›› 2009, Vol. 33 ›› Issue (6): 1184-1190.DOI: 10.3773/j.issn.1005-264x.2009.06.019

• 研究论文 • 上一篇    下一篇

不同碱度条件下中华水韭昼夜CO2气体交换的特征

顾舒平1,2, 尹黎燕1,3, 李洁琳1,2, 李伟1,4,*()   

  1. 1 中国科学院武汉植物园,武汉 430074
    2 中国科学院研究生院,北京 100049
    3 中国科学院水生植物与流域生态重点实验室,武汉 430074
    4 湿地演化与生态恢复湖北省重点实验室,武汉 430074
  • 收稿日期:2008-12-23 接受日期:2009-05-15 出版日期:2009-12-23 发布日期:2009-11-30
  • 通讯作者: 李伟
  • 作者简介:*(liwei@wbgcas.cn)
  • 基金资助:
    国家自然科学基金(30700083);国家自然科学基金(30870259);中国科学院知识创新工程重要方向项目(KSCX2-YW-Z-050)

DIURNAL CO<sub>2</sub> EXCHANGE RATES OF THE AQUATIC CRASSULACEAN ACID METABOLISM PLANT ISOETES SINENSIS PALMER AT DIFFERENT ALKALINITIES

GU Shu-Ping1,2, YIN Li-Yan1,3, LI Jie-Lin1,2, LI Wei1,4,*()   

  1. 1 Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
    2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China
    3 Key Laboratory of Aquatic Botany and Watershed Ecology, Chinese Academy of Sciences, Wuhan 430074, China
    4 Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan 430074, China
  • Received:2008-12-23 Accepted:2009-05-15 Online:2009-12-23 Published:2009-11-30
  • Contact: LI Wei

摘要:

运用pH-drift的方法研究了在不同碱度条件下中华水韭(Isoetes sinensis)的沉水叶片昼夜CO2吸收的特征。结果表明中华水韭的沉水叶片具有昼夜吸收水中CO2的能力, 而不具备利用水中的HCO- 3的能力, 进一步证明了水生植物中华水韭的光合碳同化途径具有景天酸代谢(CAM)的特征。中华水韭沉水叶片光照条件下对水中CO2的吸收速率在一定的浓度范围内正相关于水中的CO2浓度。光照条件下, 中华水韭的pH-drift实验的pH补偿点分别为(8.1±0.3)和(7.9±0.1) mmol·L-1, 最终[CT]/Alk值为(1.009±0.01)和(1.022±0.004)。碱度对中华水韭夜晚CO2的吸收速率有显著的影响(F = 38.73, p< 0.000 1)。总碱度1.70 mmol·L-1溶液中的中华水韭沉水叶片在相对较低的CO2浓度(0.04±0.001 mmol·L-1)水平下即表现出对CO2的净吸收。调查了野外一处中华水韭沉水种群的生境pH值及CO2浓度的昼夜变化, 发现水体碱度约为1.59 mmol·L-1, 一昼夜的pH值波动不大, 平均为(6.1±0.04), 昼夜CO2浓度存在波动, 午夜水中的CO2浓度是午后的近3倍。

关键词: 中华水韭, 光合作用, 景天酸代谢, CO2气体交换, 碱度

Abstract:

Aims Isoetes sinensis Palmer, an endangered aquatic plant in China, possesses a CAM (Crassulacean acid metabolism) photosynthetic pathway in its submerged leaves. Our objectives were to investigate diurnal CO2 exchange characteristics of submerged leaves and to examine if I. sinensis was capable of net CO2 uptake in the dark, which was considered evidence of the CAM pathway in aquatic plants by Keeley (1998), and determine if diurnal CO2 exchange rates were influenced by alkalinity. Results may contribute to conservation of this endangered plant by determining if high alkalinity of water sources limited population sizes.
Methods We used the pH-drift technique to analyze CT (total carbon) and CO2 uptake at two alkalinities in light and dark conditions. Photosynthetic CT/CO2 response curves were measured at 25 °C and 210 μmol·m -2·s-1 and in a solution designed by Smart and Barko (1985) in which concentrations of NaHCO3and KHCO3 were varied to supply different alkalinities. Leaves were placed in a small glass chamber, each containing a known volume of the solution which was stirred by a magnetic stirrer at the bottom. The pH/unit time was recorded by a pH electrode that had been calibrated at the beginning and the end of each experiment, the alkalinities of the solution was measured by Gran titration (Talling, 1973) to determine if alkalinity was constant during each experiment. Plant material was weighed after drying overnight at 80 °C. We calculated the concentration of free CO 2 and total carbon based on alkalinity, pH, conductivity and temperature according to Mackereth et al. (1978). With the calculated concentration of CT (or CO2), unit time, chamber volume and amount of plant material present, a photosynthesis or net CO2 exchange rate was obtained. For each alkalinity, the CO2 exchange rate was then plotted against the mean concentration of CO2. A covariance approach was used to check if the CO2 exchange significantly differed at two alkalinities.
Important findings Submerged leaves were capable of net CO2 uptake in both light and dark conditions. The CO2 uptake rate was a function of the concentration of CO2 in the medium. The CO2 uptake in dark was significantly influenced by alkalinity of the medium. Alkalinity does not seem to be a significant factor in reducing the distribution and success of this aquatic species.

Key words: Isoetes sinensisPalmer, photosynthesis, crassulacean acid metabolism, CO2 exchange, alkalinity