Dados do Trabalho

Título

DISTRIBUTION AND SPECIATION OF FOLIAR MANGANESE IN EUCALYPTUS BY SYNCHROTRON TECHNIQUES HIGHLIGHT ITS DETOXIFICATION MECHANISMS

Resumo

This is the first study to investigate the speciation and distribution patterns of high manganese (Mn) in eucalypt leaves by X-ray fluorescence (µ-XRF) and absorption near-edge spectroscopy (XANES) using synchrotron radiation. Eucalyptus tereticornis is a tree species with great economic value and potential to accumulate and tolerate high Mn despite not considered a hyperaccumulator. Seedlings grew in glasshouse conditions under two Mn treatments: irrigation with a control Mn solution (9 µM) and high Mn solution (1000 µM). Biomass, chlorophyll and total nutrient concentrations were assessed in different plant orangs and Mn, calcium (Ca) and potassium (K) localisation were determined by µ-SXRF in different foliar structures, while Mn speciation was conducted in these same compartments by XANES (Brazilian Synchrotron Light Laboratory - LNLS). Leaf biomass was unaffected by elevated Mn uptake and higher chlorophyll was observed this condition, despite reaching foliar concentrations of 1364 mg/kg Mn. Under high supply, Mn was distributed across the leaf mesophyll suggesting vacuolar sequestration in these cells and, in this condition, cytosolic Ca reduced by almost 50% in mesophyll cells, but K remained unaltered. Co-localization spots between high Mn and Ca indicate Mn deposition into oxalate crystals and speciation suggests that a great Mn fraction is complexed by malate and citrate, instead of as free Mn ion or oxidised forms. These three detoxification mechanisms: vacuolar sequestration, crystal deposition and complexation, may be responsible for the impressive Mn tolerance found in eucalypts.

Palavras-chave

heavy metal; phytotoxicity; phytoremediation; soil pollution

Instituição financiadora

FAPESP: 2019/10243-4, 2016/25498-0; CNPq: 306002/2020-5, 303664/2020-7

Agradecimentos

Drs. Renata S. Rabelo, Carla C. Pólo e Simone Betim