Convergence of a specialized root trait in plants from nutrient-impoverished soils: phosphorus-acquisition strategy in a nonmycorrhizal cactus

Autor(es)

Abrahao, A. ^[1] ; Lambers, H. ^[2] ; Sawaya, A. C. H. F. ^[1] ; Mazzafera, P. ^[1] ; Oliveira, R. S. ^{[1, 2]}

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, UNICAMP, Inst Biol, Dept Biol Vegetal, Campinas, SP - Brazil

^[2] Univ Western Australia, Sch Plant Biol, Perth, WA 6009 - Australia

• Tipo de documento: Artigo Científico
• Fonte: Oecologia; v. 176, n. 2, p. 345-355, OCT 2014.
• Citações Web of Science: 25

Resumo

In old, phosphorus (P)-impoverished habitats, root specializations such as cluster roots efficiently mobilize and acquire P by releasing large amounts of carboxylates in the rhizosphere. These specialized roots are rarely mycorrhizal. We investigated whether Discocactus placentiformis (Cactaceae), a common species in nutrient-poor campos rupestres over white sands, operates in the same way as other root specializations. Discocactus placentiformis showed no mycorrhizal colonization, but exhibited a sand-binding root specialization with rhizosheath formation. We first provide circumstantial evidence for carboxylate exudation in field material, based on its very high shoot manganese (Mn) concentrations, and then firm evidence, based on exudate analysis. We identified predominantly oxalic acid, but also malic, citric, lactic, succinic, fumaric, and malonic acids. When grown in nutrient solution with P concentrations ranging from 0 to 100 mu M, we observed an increase in total carboxylate exudation with decreasing P supply, showing that P deficiency stimulated carboxylate release. Additionally, we tested P solubilization by citric, malic and oxalic acids, and found that they solubilized P from the strongly P-sorbing soil in its native habitat, when the acids were added in combination and in relatively low concentrations. We conclude that the sand-binding root specialization in this nonmycorrhizal cactus functions similar to that of cluster roots, which efficiently enhance P acquisition in other habitats with very low P availability. (AU)

• Processo FAPESP: 10/17204-0 - Mudanças climáticas em montanhas brasileiras: respostas funcionais de plantas nativas de campos rupestres e campos de altitude a secas extremas
• Beneficiário: Rafael Silva Oliveira
• Modalidade de apoio: Auxílio à Pesquisa - Regular