Does elevated atmospheric CO2 concentration inhibit mitochondrial respiration in green plants?

There is abundant evidence that a reduction in mitochondrial respiration of plants occurs when atmospheric CO2 (C-a) is increased. Recent reviews sugg est that doubling the present C-a will reduce the respiration rate [per uni t dry weight (DW)] by 15 to 18%. The effect has two components: an immediat e, reversible effect observed in leaves, stems, and roots of plants as well as soil microbes, and an irreversible effect which occurs as a consequence of growth in elevated C-a and appears to be specific to C-3 species. The d irect effect has been correlated with inhibition of certain respiratory enz ymes, namely cytochrome-c-oxidase and succinate dehydrogenase, and the indi rect or acclimation effect may be related to changes in tissue composition. Although no satisfactory mechanisms to explain these effects have been dem onstrated, plausible mechanisms have been proposed and await experimental t esting. These are carbamylation of proteins and direct inhibition of enzyme s of respiration. A reduction of foliar respiration of 15% by doubling pres ent ambient C-a would represent 3 Gt of carbon per annum in the global carb on budget.