Effects of inorganic carbon source on photosynthetic rates of Egeria najas Planchon and Egeria densa Planchon (Hydrocharitaceae)

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• 作者：Pierini ; S.A. ; Thomaz ; S.M.
• 关键词：Egeria najas ; Egeria densa ; Photosynthesis ; Inorganic carbon ; Rooted macrophytes
• 刊名：Aquatic Botany
• 出版年：2004
• 出版时间：February, 2004
• 年：2004
• 卷：78
• 期：2
• 页码：135-146
• 全文大小：170 K

文摘

The ability of two submerged freshwater macrophyte species, Egeria najas Planchon and Egeria densa Planchon to use HCO₃⁻ as a source of inorganic carbon for photosynthesis was assessed by a pH drift experiment. The pH values and different HCO₃⁻ concentrations were set up at the beginning of the experiments, in low and high alkalinities (ca. 100 and 800μmol). Results of pH drift experiment and [C_T]/Alk quotient indicated that both species used HCO₃⁻ and were adapted to low inorganic carbon availability. Nevertheless, different efficiencies of HCO₃⁻ use were evident based on the photosynthesis rates and pH values attained at the end of the experiments. Higher photosynthesis rates and pH values were observed in the presence of E. najas both at low and high alkalinities. Both species used more efficiently HCO₃⁻ in high alkalinity. The results suggest that the efficiency in using HCO₃⁻ depends on the concentration of this ion in water uptake ability of these species. Both E. najas and E. densa preferred CO₂ in both alkalinities. By adjusting the data with a Michaelis–Menten equation, it was shown that E. najas is slightly more efficient in using CO₂ than E. densa, when the concentrations of this dissolved gas in water are low. Thus, the low CO₂ concentrations characteristic of several Brazilian freshwater ecosystems may be advantageous to the colonization of E. najas, compared to E. densa.