In the literature review the current status of information on the genetic variation of CO2 exchange and some reviews and investigations on this subject are listed. Photorespiration is separately discussed and unpublished data of an electron microscope study of poplar leaf microbodies are presented.
Considerable genetic inter- and intraspecific variation is found in several characteristics that affect CO2 exchange in trees. Photosynthesis in young trees does not correlate well with growth through the whole rotation cycle. A special interest has been shown to marginal environmental conditions (e.g. water deficit, low temperature, and low light intensity), as opposed to optimal conditions often employed in laboratory studies of CO2 exchange in trees.
In an unpublished poplar studies by the author et.al. a preliminary experiment with poplar clones showed variation in the CO2 competition point. This variation was negatively correlated with the photosynthesis efficiency of these clones.
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