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Oecologia. 2003 Dec;137(4):547-56. Epub 2003 Sep 17.

The resource economics of chemical and structural defenses across nitrogen supply gradients.

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1
100 Ecology, University of Minnesota, 1987 Upper Buford, Saint Paul, MN 55108, USA. crain010@umn.edu

Abstract

In order to better understand the role of nutrient supplies in determining the prevalence of plant defense types, we investigated the theoretical relationships between ecosystem N supply and the net C gain of shoots that were undefended or defended in one of three ways: (1) by N-free chemical compounds, (2) by N-containing chemical compounds, or (3) by structural defenses. By extending economic models of shoot resource balance to include the relative value of C and N, depreciation, and amortization, we were able to show that the relative net C gain of the three defense types were similar to changes in their generally understood abundance along an N supply gradient. At low N supply, the additional C acquired when investing C in defense is much higher than investing N in defenses. Only at high N supply is it better to invest large quantities of N in defense rather than additional photosynthesis. In a sensitivity analysis, net C gain of shoots was most sensitive to factors that affect the relative value of C and N and the rate of herbivory. Although there is support for the relative value of C and N influencing defense strategies, more research is necessary to understand why tannins are not more prevalent at high N supply and why moderate amounts of N-based defenses are not used at low N supply.

PMID:
13680348
DOI:
10.1007/s00442-003-1370-9
[Indexed for MEDLINE]
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