Gevuina avellana and Lomatia dentata, two Proteaceae species from evergreen temperate forests of South America exhibit contrasting physiological responses under nutrient deprivation

Abstract

Gevuina avellana and Lomatia dentata are Proteaceae species from evergreen temperate forests, but only G. avellana can colonize nutrient deprived volcanic depositions. We hypothesized that under nutrient deprivation, G. avellana would present higher survival, physiological performance, and adjustment regarding cluster root (CR) formation and carboxylate exudation rate than L. dentata. We evaluated relative growth rate, maximal photosynthetic rate, photochemical performance, nitrogen (N) and phosphorus (P) leaf concentrations, specific leaf area, photosynthetic P and N use efficiency (PPUE and PNUE), CR formation and carboxylate exudation rate. Plants were grown in a greenhouse, using recent volcanic substrate and watered with different nutrient Hoagland (H) solutions: modified full Hoagland, without P, without N, or tap water. Both species showed high survival. G. avellana exhibited higher growth rates (RGR), and higher CR number and biomass allocation under nutrient deprivation, but lower carboxylate exudation rates than L. dentata. Malate, oxalate and succinate were detected in root exudates of G. avellana but only oxalate in L. dentata. However, PPUE and PNUE were higher in L. dentata than in G. avellana . Our hypothesis was not entirely accepted, CR formation was more “constitutive” in G. avellana, and composition of carboxylates was more diverse, with lower exudation rates than L. dentata. Moreover, L. dentata showed higher PNUE and PPUE, partly explained by thinner leaves. Different responses are related with edaphic conditions, where both species inhabit: more diverse to G. avellana and restricted to developed soils to L. dentata.