314
1.A. Raven
and De Niro 1989). The extent to which this constitutes evidence for
rehydration from water vapor is debatable, but evidence for such a mechanism in intertidal plants should be sought. A start has been made by
Britting (1992) in her work on the high intertidal red alga Endocladia
muricata.
15.8 Conclusions
Photosynthesis in aquatic plants must be viewed in the context of the great
diversity of these plants. The primarily aquatic plants have a much greater
diversity of light-harvesting pigments than do secondarily aquatic plants (or
their terrestrial ancestors). The ecophysical significance of the variety of
pigments is likely to be greater in the smallest (picoplanktonic) aquatic
plants than in larger plants as result of differences in the package effect.
The majority of aquatic plants acquire inorganic carbon by a mechanism
more complex than CO2 diffusion in solution from the bulk phase to
Rubisco. The occurrence of these COr concentrating mechanisms is related
to low CO2 diffusivity in water (especially significant for larger plants) and
the properties of Rubisco in aquatic plants. The diversity of mechanisms of
inorganic carbon acquisition is, by contrast to light-harvesting machinery,
greater in secondarily than primarily aquatic plants. The diversity of CO2
acquisition mechanisms may have significance for the extent of carbon assimilation during emersion in intertidal plants.
The availability of light, and of nutrients other than carbon, is probably a
more significant abiotic factor limiting net primary productivity of aquatic
plants than is the supply of inorganic carbon. However, the mechanism by
which inorganic carbon is acquired by aquatic plants may affect the need for
photons or other nutrients for photosynthesis.
The most important conclusion is, however, that we are still very ignorant
of the ecophysiology of photosynthesis by aquatic plants relative to what is
known about their terrestrial counterparts; it would be very helpful if some
Lange clones tackled some of these problems.
Acknowledgments. Work on resource acquisition by aquatic plants in the author's laboratory has been supported by S.E.R.C., N.E.R.C., the Nuffield Foundation and the
British Council; it is currently supported by N.E.R.C. Interaction with past and present
colleagues has been very important in arriving at the views expressed here.
References
Alberte RS (1989) Physiological and cellular features of Prochloron. In: Lewin RA,
Cheng L (eds) Prochloron: a microbial enigma. Chapman and Hall, New York, pp
31-52
1.A. Raven
and De Niro 1989). The extent to which this constitutes evidence for
rehydration from water vapor is debatable, but evidence for such a mechanism in intertidal plants should be sought. A start has been made by
Britting (1992) in her work on the high intertidal red alga Endocladia
muricata.
15.8 Conclusions
Photosynthesis in aquatic plants must be viewed in the context of the great
diversity of these plants. The primarily aquatic plants have a much greater
diversity of light-harvesting pigments than do secondarily aquatic plants (or
their terrestrial ancestors). The ecophysical significance of the variety of
pigments is likely to be greater in the smallest (picoplanktonic) aquatic
plants than in larger plants as result of differences in the package effect.
The majority of aquatic plants acquire inorganic carbon by a mechanism
more complex than CO2 diffusion in solution from the bulk phase to
Rubisco. The occurrence of these COr concentrating mechanisms is related
to low CO2 diffusivity in water (especially significant for larger plants) and
the properties of Rubisco in aquatic plants. The diversity of mechanisms of
inorganic carbon acquisition is, by contrast to light-harvesting machinery,
greater in secondarily than primarily aquatic plants. The diversity of CO2
acquisition mechanisms may have significance for the extent of carbon assimilation during emersion in intertidal plants.
The availability of light, and of nutrients other than carbon, is probably a
more significant abiotic factor limiting net primary productivity of aquatic
plants than is the supply of inorganic carbon. However, the mechanism by
which inorganic carbon is acquired by aquatic plants may affect the need for
photons or other nutrients for photosynthesis.
The most important conclusion is, however, that we are still very ignorant
of the ecophysiology of photosynthesis by aquatic plants relative to what is
known about their terrestrial counterparts; it would be very helpful if some
Lange clones tackled some of these problems.
Acknowledgments. Work on resource acquisition by aquatic plants in the author's laboratory has been supported by S.E.R.C., N.E.R.C., the Nuffield Foundation and the
British Council; it is currently supported by N.E.R.C. Interaction with past and present
colleagues has been very important in arriving at the views expressed here.
References
Alberte RS (1989) Physiological and cellular features of Prochloron. In: Lewin RA,
Cheng L (eds) Prochloron: a microbial enigma. Chapman and Hall, New York, pp
31-52