ABSTRACT After defoliation by herbivores, some plants exhibit enhanced rates of photosynthesis and growth that enable them to compensate for lost tissue, thus maintaining their fitness relative to competing, undefoliated plants. Our aim was to determine whether compensatory photosynthesis and growth would be altered by increasing concentrations of atmospheric CO 2 . Defoliation of developing leaflets on seedlings of a tropical tree, Copaifera aromatica , caused increases in photosynthesis under ambient CO 2 , but not under elevated CO 2 . An enhancement in the development of buds in the leaf axils followed defoliation at ambient levels of CO 2 . In contrast, under elevated CO 2 , enhanced development of buds occurred in undefoliated plants with no further enhancement in bud development due to exposure to elevated CO 2 . Growth of leaf area after defoliation was increased, particularly under elevated CO 2 . Despite this increase, defoliated plants grown under elevated CO 2 were further from compensating for tissue lost during defoliation after 5 1 / 2 weeks than those grown under ambient CO 2 concentrations.