![]() on substrate availability) and downstream (e.g. Scaling the effects of an increase in atmospheric on plant respiration at the biochemical level to the whole ecosystem is difficult for at least two important reasons: (1) the fine and coarse control points of respiratory pathways in tissues and whole plants are not well known and (2) it is unclear how respiration rates actively or passively adjust to the effects that elevated may have both upstream (e.g. Therefore, not only are gross changes in respiration important for large-scale carbon balance issues, changes in specific rates of respiration can have significant impact on basic plant biology such as growth, biomass partitioning or nutrient uptake ( Amthor, 1991 Wullschleger et al., 1994 Drake et al., 1999). For example, it was estimated that the observed 15–20 % reduction in plant tissue respiration caused by doubling current atmospheric ( Amthor, 1997 Drake et al., 1997 Curtis and Wang, 1998), could increase the net sink capacity of global ecosystems by 3♴ Gt of carbon per year ( Drake et al., 1999), and thus offset an equivalent amount of carbon from anthropogenic CO 2 emissions. A large body of literature has indicated that plant respiration is reduced in plants grown at high. Because terrestrial biosphere-atmosphere fluxes of CO 2 far outweigh anthropogenic inputs of CO 2 to the atmosphere, a small change in terrestrial respiration could have a significant impact on the annual increment in atmospheric ( Amthor, 1997). ![]() Roughly, half of the CO 2 assimilated annually through photosynthesis is released back to the atmosphere by plant respiration ( Gifford, 1994 Amthor, 1995). Terrestrial ecosystems exchange about 120 Gt of carbon per year with the atmosphere, through the processes of photosynthesis and respiration ( Schlesinger, 1997). A quantitatively important by-product of respiration is CO 2 and, therefore, plant and ecosystem respiration play a major role in the global carbon cycle. Through the processes of respiration, solar energy conserved during photosynthesis and stored as chemical energy in organic molecules is released in a regulated manner for the production of ATP, the universal currency of biological energy transformations, and reducing power (e.g. Respiration is essential for growth and maintenance of all plant tissues, and plays an important role in the carbon balance of individual cells, whole-plants and ecosystems, as well as in the global carbon cycle. Therefore the role of plant respiration in augmenting the sink capacity of terrestrial ecosystems is still uncertain. ![]() Fundamental information is still lacking on how respiration and the processes supported by it are physiologically controlled, thereby preventing sound interpretations of what seem to be species-specific responses of respiration to elevated. ![]() ![]() However, whole ecosystem studies show that canopy respiration does not increase proportionally to increases in biomass in response to elevated, although a larger proportion of respiration takes place in the root system.
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