RESPIRATORY RESPONSES OF HIGHER-PLANTS TO ATMOSPHERIC CO2 ENRICHMENT

Although the respiratory response of native and agricultural plants to atmospheric CO2 enrichment has been reported over the past 75 years, only recently have these effects emerged as prominent measures of plan t and ecosystem response to the earth's changing climate. In this revi ew we discuss this rapidly expanding field of study and propose that b oth increasing and decreasing rates of leaf and whole-plant respiratio n are likely to occur in response to rising CO2 concentrations. While the stimulatory effects of CO2 on respiration are consistent with our knowledge of leaf carbohydrate status and plant metabolism, we wish to emphasize the rather surprising short-term inhibition of leaf respira tion by elevated CO2 and the reported effects of long-term CO2 exposur e on growth and maintenance respiration. As is being found in many stu dies, it is easier to document the respiratory response of higher plan ts to elevated CO2 than it is to assign a mechanistic basis for the ob served effects. Despite this gap in our understanding of how respirati on is affected by CO2 enrichment, data are sufficient to suggest that changes in leaf and whole-plant respiration may be important considera tions in the carbon dynamics of terrestrial ecosystems as global CO2 c ontinues to rise. Suggestions for future research that would enable th ese and other effects of CO2 on respiration to be unravelled are prese nted.