Effects of inorganic carbon source on photosynthetic rates of Egeria najas Planchon and Egeria densa Planchon (Hydrocharitaceae)
The ability of two submerged freshwater macrophyte species, Egeria najas Planchon and Egeria densa Planchon to use HCO 3 − as a source of inorganic carbon for photosynthesis was assessed by a pH drift experiment. The pH values and different HCO 3 − concentrations were set up at the beginning of the...
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| Published in: | Aquatic botany Vol. 78; no. 2; pp. 135 - 146 |
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| Main Authors: | , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Elsevier B.V
01-02-2004
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | The ability of two submerged freshwater macrophyte species,
Egeria najas Planchon and
Egeria densa Planchon to use HCO
3
− as a source of inorganic carbon for photosynthesis was assessed by a pH drift experiment. The pH values and different HCO
3
− concentrations were set up at the beginning of the experiments, in low and high alkalinities (ca. 100 and 800
μmol). Results of pH drift experiment and [C
T]/Alk quotient indicated that both species used HCO
3
− and were adapted to low inorganic carbon availability. Nevertheless, different efficiencies of HCO
3
− 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 HCO
3
− in high alkalinity. The results suggest that the efficiency in using HCO
3
− depends on the concentration of this ion in water uptake ability of these species. Both
E. najas and
E. densa preferred CO
2 in both alkalinities. By adjusting the data with a Michaelis–Menten equation, it was shown that
E. najas is slightly more efficient in using CO
2 than
E. densa, when the concentrations of this dissolved gas in water are low. Thus, the low CO
2 concentrations characteristic of several Brazilian freshwater ecosystems may be advantageous to the colonization of
E. najas, compared to
E. densa. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 ObjectType-Article-2 ObjectType-Feature-1 |
| ISSN: | 0304-3770 1879-1522 |
| DOI: | 10.1016/j.aquabot.2003.09.007 |