Datensatz

Zusammenfassung

Lloyd & Farquhar 1996 addressed the effect of elevated [CO₂] on the relationships between photosynthesis, plant growth and their interaction with soil nitrogen availability. Using a quantitative approach the contrasting nature of photosynthetic vs. growth responses to elevated [CO₂] was discussed. The importance of genetic and environmental differences in plant respiratory costs was also emphasized. In examining the importance of variation in soil nitrogen availability in modulating [CO₂]–growth relationships it was concluded, contrary to the widely held assumption at the time, that plant growth enhancements in response to elevated CO₂ concentrations were ‘nearly as often as not greater under low nutrient conditions’ ( Lloyd & Farquhar 1996; p. 8). A simple model of plant growth in relation to carbon and nitrogen availability accounting for this observation was then presented. In passing, likely effects of higher respiratory costs in slower growing plants on their growth response to elevated [CO₂] were also mentioned. Recently Poorter (1998) has suggested that the model of Lloyd & Farquhar (1996) is ‘not supported by the available data’ and that ‘plant growth at low nutrient supply or high CO₂ concentrations is not constrained by C-availability’. Here we show why some of the issues and hypotheses advanced in his paper may be flawed.