Performance of a generalist grasshopper on a C 3 and a C 4 grass: compensation for the effects of elevated CO 2 on plant nutritional quality

Barbehenn, R.V. and Karowe, D.N. and Chen, Z. (2004) Performance of a generalist grasshopper on a C 3 and a C 4 grass: compensation for the effects of elevated CO 2 on plant nutritional quality. Oecologia , 140 (1). pp. 96-103.

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The increasing CO2 concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C3 than C4 plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C3 plants. These hypotheses were tested by growing the grasses Lolium multiflorum C3) and Bouteloua curtipendula C4) at ambient (370 ppm) and elevated (740 ppm) CO2 levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO2 treatment combinations. As expected, the nutritional quality of the C3 grass declined to a greater extent than did that of the C4 grass at elevated CO2; protein levels declined in the C3 grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C3 grass grown under elevated CO2. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C3 grass under elevated CO2. Consumption rates of the C3 and C4 grasses were also similar, demonstrating a lack of compensatory feeding on the C4 grass. We also examined the relative efficiencies of nutrient utilization from a C3 and C4 grass by M. sanguinipes to test the basis for the C4 plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C4 grass than from the C3 grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C3 grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C3 grass and the better growth performance of M. sanguinipes on this grass at both CO2 levels, we conclude that C3 grasses are likely to remain better host plants than C4 grasses in future CO2 conditions.

Item Type: Article
Uncontrolled Keywords: Melanoplus sanguinipes (grasshopper) - Lolium multiflorum C3 grass) - Bouteloua curtipendula C4 grass) - Nutrient - Digestion
Author Affiliation: Departments of Molecular, Cellular and Developmental Biology and Ecology and Evolutionary Biology University of Michigan Ann Arbor MI 48109-1048 USA, Department of Biological Sciences Western Michigan University Kalamazoo MI 49008-5410 USA, School of Forestry Northern Arizona University Flagstaff AZ 86011-5018 USA
Subjects: Atmosperic Science > Climatology
Postharvest Management > Food Technology
Divisions: General
Depositing User: Mr. SanatKumar Behera
Date Deposited: 26 Mar 2012 05:09
Last Modified: 26 Mar 2012 05:09
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