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

Authors: Jep Agrell¹; Peter Anderson²; Wieslaw Oleszek³; Anna Stochmal³; Cecilia Agrell⁴

Source: Journal of Chemical Ecology, Volume 30, Number 11, November 2004 , pp. 2309-2324(16)

Publisher: Springer

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Abstract:

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- beta

-D-glucuronopyranozyl (1 rarr

2)-O-

-D-glucuronopyranozyl]-4 prime

-O-

-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.

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

Document Type: Research article

DOI: http://dx.doi.org/10.1023/B:JOEC.0000048791.74017.93

Affiliations: 1: Department of Animal Ecology, Ecology Building, Lund University, S-223 62 Lund, Sweden;, Email: jep.agrell@zooekol.lu.se 2: Department of Crop Science, Swedish University of Agricultural Sciences, SE-230 53 Alnarp, Sweden 3: Department of Biochemistry, Institute of Soil Science and Plant Cultivation, 24-100 Pulawy, Poland 4: Department of Chemical Ecology and Ecotoxicology, Lund University, SE-223 62 Lund, Sweden

Publication date: 2004-11-01