562
E.-D. Schulze and M.M. Caldwell
recognized that most of the production of photosynthates occurs only
when water is available. Thus, responses of plants to water deficits are
more important with respect to survival rather than with respect to more
production. Water-use efficiency is important and stomatal behavior
receives attention; however, this may slacken. Kelliher et al. (1993)
showed that functional rooting depth may be more important than canopy
conductance in avoiding water stress. In turn, functional rooting depth is
related to carbon partitioning and nutrition.
Species-specific interactions in ecosystem function will remain a major
challenge. The competitive interactions among plants usually result in a
rather complete use of resources. However, predicting changes in species
composition in future environmental scenarios is only in the early stages
of development.
- Despite all the knowledge collected concerning photosynthetic processes,
there is still considerable uncertainty in making predictions on wholeplant performance at elevated CO2 due to feedbacks within the plant.
Even the question of some degree of down-regulation is far from settled.
If less protein is needed in order to achieve a certain carbon gain, then
down-regulation might be the appropriate response, as it would release
plant internal resources for further growth and carbon investment in
other components of the plant. This, in turn, may affect water relations
and mineral nutrition at the whole-plant level. We cannot model this
interaction without experimental evidence on plant response at high CO2
under a range of field conditions.
Although the ecophysiology of photosynthesis has come a long way, it is
still far from being predictive at a global scale. The challenges of scaling
up from plants to canopies, landscapes, and even a global level will drive
many efforts in modeling and innovative approaches to validation of these
models.
References
Bjorkman 0 (1981) Responses to different quantum flux densities. In: Lange OL, Nobel
PS, Osmond CB, Ziegler H (eds) Encyclopedia of plant physiology vol 12A. Springer,
Berlin Heidelberg New York, pp 57-108
Boysen-Jensen P, Muller D (1929) Die maximale Ausbeute und der tagliche Verlauf der
Kohlensaureassimilation. Jahrb Wiss Bot 70: 493-502
Conway TJ, Tans P, Waterman LS, Thoning KW, Masarie KA, Gammon RH (1988)
Atmospheric carbon dioxide measurements in the remote global troposphere 19811984. Tellus 40B: 81-115
Egle K, Ernst A (1949) Die Verwendung des Ultrarotabsorptionsschreibers fUr die
vollautomatische und fortlaufende COz-Analyse bei Assimilations- und Atmungsmessungen an Pflanzen. Z Naturforsch 4b: 351-360
E.-D. Schulze and M.M. Caldwell
recognized that most of the production of photosynthates occurs only
when water is available. Thus, responses of plants to water deficits are
more important with respect to survival rather than with respect to more
production. Water-use efficiency is important and stomatal behavior
receives attention; however, this may slacken. Kelliher et al. (1993)
showed that functional rooting depth may be more important than canopy
conductance in avoiding water stress. In turn, functional rooting depth is
related to carbon partitioning and nutrition.
Species-specific interactions in ecosystem function will remain a major
challenge. The competitive interactions among plants usually result in a
rather complete use of resources. However, predicting changes in species
composition in future environmental scenarios is only in the early stages
of development.
- Despite all the knowledge collected concerning photosynthetic processes,
there is still considerable uncertainty in making predictions on wholeplant performance at elevated CO2 due to feedbacks within the plant.
Even the question of some degree of down-regulation is far from settled.
If less protein is needed in order to achieve a certain carbon gain, then
down-regulation might be the appropriate response, as it would release
plant internal resources for further growth and carbon investment in
other components of the plant. This, in turn, may affect water relations
and mineral nutrition at the whole-plant level. We cannot model this
interaction without experimental evidence on plant response at high CO2
under a range of field conditions.
Although the ecophysiology of photosynthesis has come a long way, it is
still far from being predictive at a global scale. The challenges of scaling
up from plants to canopies, landscapes, and even a global level will drive
many efforts in modeling and innovative approaches to validation of these
models.
References
Bjorkman 0 (1981) Responses to different quantum flux densities. In: Lange OL, Nobel
PS, Osmond CB, Ziegler H (eds) Encyclopedia of plant physiology vol 12A. Springer,
Berlin Heidelberg New York, pp 57-108
Boysen-Jensen P, Muller D (1929) Die maximale Ausbeute und der tagliche Verlauf der
Kohlensaureassimilation. Jahrb Wiss Bot 70: 493-502
Conway TJ, Tans P, Waterman LS, Thoning KW, Masarie KA, Gammon RH (1988)
Atmospheric carbon dioxide measurements in the remote global troposphere 19811984. Tellus 40B: 81-115
Egle K, Ernst A (1949) Die Verwendung des Ultrarotabsorptionsschreibers fUr die
vollautomatische und fortlaufende COz-Analyse bei Assimilations- und Atmungsmessungen an Pflanzen. Z Naturforsch 4b: 351-360