Journal of Chemical Ecology

, Volume 30, Issue 11, pp 2309-2324

First online:

Combined Effects of Elevated Co2 and Herbivore Damage on Alfalfa and Cotton

  • Jep AgrellAffiliated withDepartment of Animal Ecology, Ecology Building, Lund University
  • , Peter AndersonAffiliated withDepartment of Crop Science, Swedish University of Agricultural Sciences
  • , Wieslaw OleszekAffiliated withDepartment of Biochemistry, Institute of Soil Science and Plant Cultivation
  • , Anna StochmalAffiliated withDepartment of Biochemistry, Institute of Soil Science and Plant Cultivation
  • , Cecilia AgrellAffiliated withDepartment of Chemical Ecology and Ecotoxicology, Lund University

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We examined herbivore-induced responses of alfalfa (Medicago sativa) and cotton (Gossypium hirsutum) under different CO2 conditions. Plants were grown under ambient (350 ppm) or elevated (700 ppm) CO2 levels, and were either damaged or undamaged by Spodoptera littoralis larvae. At harvest, growth of undamaged (control) plants was determined, and foliar chemical composition of both undamaged and damaged plants was analyzed. Cotton grew faster overall and showed a greater increase in growth in response to CO2 enrichment than did alfalfa. Elevated CO2 levels increased starch and decreased nitrogen levels in damaged alfalfa and undamaged cotton plants. Alfalfa saponin levels were significantly increased by elevated CO2 and damage. Regarding specific saponins, medicagenic acid bidesmoside (3GlcA,28AraRhaXyl medicagenate) concentrations were reduced by high CO2, whereas zanhic acid tridesmoside (3GlcGlcGlc,23Ara,28AraRhaXylApi Za) levels were unaffected by the treatments. Soyasaponin I (3GlcAGalRha soyasapogenol B) was only detected in minute amounts. Alfalfa flavonoid analyses showed that total flavonoid levels were similar between treatments, although free apigenin increased and apigenin glucoside (7-O-[2-O-feruloyl-β-D-glucuronopyranozyl (1→2)-O-β-D-glucuronopyranozyl]-4′-O-β-D-glucuronopyranozide apigenin) decreased in CO2-enriched plants. In cotton, herbivore damage increased levels of total terpenoid aldehydes, gossypol, hemigossypolone, the heliocides H1 and H4, but not H2 and H3, whereas CO2 enrichment had no effect. These results demonstrate that combined effects of CO2 and herbivore damage vary between plant species, which has implications for the competitive balance within plant communities.

CO2 enrichment induced response secondary compounds cotton alfalfa saponins flavonoids terpenoid aldehydes phytochemistry