Direct inhibition of maintenance respiration in western hemlock roots exposed to ambient soil carbon dioxide concentrations.

摘要

Root respiration often exhibits a direct and immediate decline with increasing concentrations of ambient soil carbon dioxide concentration ([CO2]), and recent evidence suggests this decline may be attributable to a decline in maintenance respirationwithin the root. To test the hypothesis that maintenance respiration exhibits a direct, negative response to increasing [CO2], total respiration was measured in intact root systems of western hemlock (Tsuga heterophylla) seedlings grown at different relative growth rates and exposed to soil [CO2]s ranging from 91 to 7008μmol mol-1. Analysis of covariance was used to separate maintenance from total respiration. Total respiration declined exponentially with increasing [CO2]. Maintenance respiration, which comprised 85% of total respiration over all treatments, also declined exponentially with increasing [CO2]. Growth respiration was not inhibited at any [CO2]. These findings may explain why roots of some fast-growing species do not show [CO2] inhibition.