Abstract
This study explores how elevated carbon dioxide (CO(2)) levels affects the growth and defense mechanisms of plants. We focused on Aristolochia contorta Bunge (Aristolochiaceae), a wild plant that exhibits growth reduction under elevated CO(2) in the previous study. The plant has Sericinus montela Gray (Papilionidae) as a specialist herbivore. By analyzing primary metabolites, understanding both the growth and defense response of plants to herbivory under elevated CO(2) conditions is possible. The experiment was conducted across four groups, combining two CO(2) concentration conditions (ambient CO(2) and elevated CO(2)) with two herbivory conditions (herbivory treated and untreated). Although many plants exhibit increased growth under elevated CO(2) levels, A. contorta exhibited reduced growth with lower height, dry weight, and total leaf area. Under herbivory, A. contorta triggered both localized and systemic responses. More primary metabolites exhibited significant differences due to herbivory treatment in systemic tissue than local leaves that herbivory was directly treated. Herbivory under elevated CO(2) level triggered more significant responses in primary metabolites (17 metabolites) than herbivory under ambient CO(2) conditions (five metabolites). Several defense-related metabolites exhibited higher concentrations in the roots and lower concentrations in the leaves in response to the herbivory treatment in the elevated CO(2) group. This suggests a potential intensification of defensive responses in the underground parts of the plant under elevated CO(2) levels. Our findings underscore the importance of considering both abiotic and biotic factors in understanding plant responses to environmental changes. The adaptive strategies of A. contorta suggest a complex response mechanism to elevated CO(2) and herbivory pressures.