Accumulation and localization of manganese in eucalypt species under low phosphorus availability

Abstract

Eucalypts is a group of species with great economic importance. However their development can be limited due to the low phosphorus (P) availability in tropical soils. Contrarily, manganese (Mn) is a highly available micronutrient in such soil types, and can cause phytotoxicity when in excess. Eucalypt species capable of mobilizing P in soils via exudation of organic acids into the rhizosphere are vulnerable to Mn toxicity, or able to accumulate high concentrations of this metal, suggesting a remediation potential. Due to the lack of studies involving the interactions between Mn and P, or Mn tolerance, accumulation, its form and localization in eucalypts, we propose with this project to clarify some of these questions in species with differential abilities in P acquisition from soils (E. tereticornis, E. grandis and E. acmenoides). Plants will be evaluated under three Mn concentrations (sufficient, high and very high) and two P concentrations (deficient and sufficient), with or without inoculation with mycorrhizal fungus Rhizophagus irregularis, an association closely involved in modulating P and Mn uptake. The localization, concentration and speciation of Mn and P in different plant organs will be assessed by high resolution techniques, such as: ICP-OES, LIBS and µ-XRF with synchrotron radiation (uncertain due to possible cuts in federal funding), and determination of expression of genes encoding Mn and P transporters in roots (Nramp1, Nramp3, YSL2, ZIP2 and RiPT5), by RT-qPCR. The results from all these analyses will be associated with results from several physiological analyses. (AU)