Costs of Defense and a Test of the Carbon-Nutrient Balance and Growth-Differentiation Balance Hypotheses for Two Co-Occurring Classes of Plant Defense

• DOI: 10.1371/journal.pone.0047554
• Publication Date: 2012-10-24T21:12:52Z
• Authors: Tara Joy Massad; Lee A. Dyer; Gerardo Vega C.
• Keywords: Flavonoids; 0106 biological sciences; 2. Zero hunger; Science; Q; R; Plants; 15. Life on land; 01 natural sciences; Carbon; Phenols; Medicine; Biomass; Research Article

One of the goals chemical ecology is to assess costs plant defenses. Intraspecific trade-offs between growth and defense are traditionally viewed in context carbon-nutrient balance hypothesis (CNBH) growth-differentiation (GDBH). Broadly, these hypotheses suggest that limited by deficiencies carbon or nitrogen while rates photosynthesis remain unchanged, subsequent reduced results more abundant resource being invested increased (mass-balance based allocation). The GDBH further predicts should only be observed when resources abundant. Most support for comes from work with phenolics. We examined related production two classes defenses, saponins (triterpenoids) flavans (phenolics), Pentaclethra macroloba (Fabaceae), an tree Costa Rican wet forests. quantified physiological defenses measuring photosynthetic parameters (which often assumed stable) addition biomass. were grown full sunlight shade under three levels alone conspecific neighbors could potentially alter nutrient availability via competition facilitation. Biomass not affected seedlings sunlight, but they responded positively shade-grown plants. trade-off predicted metabolite was present biomass sun-grown plants (abundant conditions). Support also partial CNBH as declined increased. This suggests saponin considered terms detailed biosynthetic pathway models phenolic fits mass-balance allocation (such CNBH). Contrary expectations on hypotheses, found photosynthesis, indicating studies include direct measures responses.