Growth and maintenance respiration in leaves of Liriodendron tulipifera L. exposed to long‐term carbon dioxide enrichment in the field

Abstract

Specific respiration rate (SRR) was mathematically partitioned into its growth and maintenance components for leaves of yellow‐poplar (Liriodendron tulipifera L.) after 3 yr of CO2 enrichment in open‐top field chambers. Despite the absence of a CO2 effect on individual leaf expansion or specific growth rate (SGR), increasing the CO2 concentration to ambient +150 or +300 cm3 m−3 decreased SRR by 28 to 45% compared with ambient‐grown controls. These lower leaf respiration rates were correlated with reduced leaf nitrogen concentrations. As described by the two‐component model of growth and maintenance respiration, SRR was a linear function of SGR. Ambient‐grown leaves had a growth respiration coefficient of 704 mg CO2 g−1 dry mass compared with 572 and 570 mg CO2 g−1 for leaves grown at the two higher CO2 concentrations. Leaves from the elevated CO2 treatments had an average maintenance respiration coefficient of 88 mg CO2 g−1 dry mass d−1 compared with 135 mg CO2 g−1 d −1 for leaves from the ambient treatment. Incorporating these growth and maintenance coefficients into a leaf growth simulation model indicated that total respiration would be reduced by 21 to 26 % for a leaf exposed to + 150 or + 300 cm3 m−3 CO2 throughout its 50‐d lifespan compared with one grown at ambient CO2 conditions. Reductions in total respiration were dominated by a lower rate of maintenance respiration, while the contribution of a lower specific rate of growth respiration was largely offset by a greater dry mass for leaves grown at elevated CO2 concentrations. Although reductions in the respiratory loss of carbon could be beneficial, respiration is unlikely to decrease without a concomitant decrease in other metabolic processes. Whether these reductions are beneficial or detrimental to the long‐term growth of plants exposed to elevated CO2 remains unresolved. Copyright © 1992, Wiley Blackwell. All rights reserved