Book contents
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- Part I The underwater light field
- Part II Photosynthesis in the aquatic environment
- 8 The photosynthetic apparatus of aquatic plants
- 9 Light capture by aquatic plants
- 10 Photosynthesis as a function of the incident light
- 11 Photosynthesis in the aquatic environment
- 12 Ecological strategies
- References and author index
- Index to symbols
- Index to organisms
- Index to water bodies
- Subject index
10 - Photosynthesis as a function of the incident light
Published online by Cambridge University Press: 25 January 2010
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- Part I The underwater light field
- Part II Photosynthesis in the aquatic environment
- 8 The photosynthetic apparatus of aquatic plants
- 9 Light capture by aquatic plants
- 10 Photosynthesis as a function of the incident light
- 11 Photosynthesis in the aquatic environment
- 12 Ecological strategies
- References and author index
- Index to symbols
- Index to organisms
- Index to water bodies
- Subject index
Summary
The rate of photosynthesis achieved by a phytoplankton cell or aquatic macrophyte depends on the rate of capture of quanta from the light field. This is determined by the light absorption properties of the photosynthetic biomass, which we have considered in some detail, and by the intensity and spectral quality of the field. The rate of photosynthesis is not, however, simply proportional to the rate of capture of photons. The efficiency with which the photosynthetic apparatus can make use of the absorbed energy to fix CO2 varies from one plant cell to another and within a given cell as its physiological state changes. Light quanta may be collected by the pigments faster than the electron carriers and enzymes can make use of them. In particularly high light intensities the excess absorbed energy can inactivate the photosynthetic system. The relation between the rate of photosynthesis and the characteristics of the incident light is thus not a simple one: we shall examine it in this chapter.
In order to study the effects of light intensity and spectral quality on photosynthesis, suitable quantitative procedures for determining the photosynthetic rate per unit biomass must be used. Detailed descriptions of such methods for use in the field or the laboratory may be found elsewhere, and so they will only be briefly mentioned here. Photosynthesis can be measured in terms of either carbon dioxide fixed or oxygen released. Because of the stoichiometry of the overall photosynthetic process (§8.5), approximately one O2 molecule is liberated for every molecule of CO2 fixed.
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- Chapter
- Information
- Light and Photosynthesis in Aquatic Ecosystems , pp. 271 - 313Publisher: Cambridge University PressPrint publication year: 1994
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