Overview: Perspectives in Ecophysiological Research of Photosynthesis
561
trations in the winter climates of higher latitudes would be a measure of
photosynthesis and respiration (and other COremitting processes). In this
case, the whole globe may be viewed as a "closed cuvetts", and one can
visualize gas exchange at a global scale, which has never before been
possible. At this scale species may not be important in describing the
present status of the globe. On the other hand, if one is to make realistic
predictions of species' migrations during global climate change and their
effect on assimilation, then issues of biodiversity must be addressed because
species will not move as communities but as solitary species, but questions
of biodiversity and ecosystem function in a changing world remain elusive at
this point (Schulze and Mooney 1993). Nevertheless, some strides in this
general direction have been made. For example, global maps of photosynthetic capacity have been drawn (Woodward, Chap. 23) which necessarily
incorporates the general distribution of major vegetation types with representative species. Surprisingly, the average rates of gas exchange (not the
photosynthetic capacity) are remarkably constant. This has been demonstrated for leaf conductance and net CO2 uptake (Korner, Chap. 22) as well
as for canopy conductance (Kelliher et al. 1993) and even for canopy
photosynthesis (Mooney and Field 1989). If this is true, then global modeling
would be greatly eased. Yet, it still would not answer questions of how
biodiversity interacts with ecosystem function. Schulze et al. (1993) concluded, that the instability at lower scales (species diversity and its densityrelated interactions) are the driving mechanisms that lead to the observed
stability at the higher scales of ecosystems. Thus, we may be able to use
canopy models ignoring species composition, but it is doubtful that these
models would be truly predictive because of secondary and tertiary effects of
species changes.
26.7 Where Will Ecophysiology of Photosynthesis Venture
in the Coming Decade? We OtTer Some Thoughts
- The link between molecular biology and ecology will be strengthened
and, by using molecular tools, much progress can be made beyond simply
correlative evidence. This is especially needed with respect to whole-plant
carbon allocation and growth, because this feeds directly back into photosynthesis at the canopy scale.
- Research of recent years has shown that studying photosynthesis in
isolation is no longer acceptable. Interactions with several other major
plant processes must be understood. For example, nutrition has emerged
as one prominent parameter and not just its influence on photosynthetic
capacity. Water relations, which has always been a central theme in
photosynthetic research, is losing some importance because it is well
561
trations in the winter climates of higher latitudes would be a measure of
photosynthesis and respiration (and other COremitting processes). In this
case, the whole globe may be viewed as a "closed cuvetts", and one can
visualize gas exchange at a global scale, which has never before been
possible. At this scale species may not be important in describing the
present status of the globe. On the other hand, if one is to make realistic
predictions of species' migrations during global climate change and their
effect on assimilation, then issues of biodiversity must be addressed because
species will not move as communities but as solitary species, but questions
of biodiversity and ecosystem function in a changing world remain elusive at
this point (Schulze and Mooney 1993). Nevertheless, some strides in this
general direction have been made. For example, global maps of photosynthetic capacity have been drawn (Woodward, Chap. 23) which necessarily
incorporates the general distribution of major vegetation types with representative species. Surprisingly, the average rates of gas exchange (not the
photosynthetic capacity) are remarkably constant. This has been demonstrated for leaf conductance and net CO2 uptake (Korner, Chap. 22) as well
as for canopy conductance (Kelliher et al. 1993) and even for canopy
photosynthesis (Mooney and Field 1989). If this is true, then global modeling
would be greatly eased. Yet, it still would not answer questions of how
biodiversity interacts with ecosystem function. Schulze et al. (1993) concluded, that the instability at lower scales (species diversity and its densityrelated interactions) are the driving mechanisms that lead to the observed
stability at the higher scales of ecosystems. Thus, we may be able to use
canopy models ignoring species composition, but it is doubtful that these
models would be truly predictive because of secondary and tertiary effects of
species changes.
26.7 Where Will Ecophysiology of Photosynthesis Venture
in the Coming Decade? We OtTer Some Thoughts
- The link between molecular biology and ecology will be strengthened
and, by using molecular tools, much progress can be made beyond simply
correlative evidence. This is especially needed with respect to whole-plant
carbon allocation and growth, because this feeds directly back into photosynthesis at the canopy scale.
- Research of recent years has shown that studying photosynthesis in
isolation is no longer acceptable. Interactions with several other major
plant processes must be understood. For example, nutrition has emerged
as one prominent parameter and not just its influence on photosynthetic
capacity. Water relations, which has always been a central theme in
photosynthetic research, is losing some importance because it is well