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Manganese distribution and speciation help to explain the effects of silicate and phosphate on manganese toxicity in four crop species
Author(s) -
Blamey F. Pax C.,
McKenna Brigid A.,
Li Cui,
Cheng Miaomiao,
Tang Caixian,
Jiang Haibo,
Howard Daryl L.,
Paterson David J.,
Kappen Peter,
Wang Peng,
Menzies Neal W.,
Kopittke Peter M.
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14878
Subject(s) - manganese , apoplast , sunflower , genetic algorithm , helianthus annuus , chemistry , toxicity , environmental chemistry , nuclear chemistry , botany , biology , horticulture , cell wall , biochemistry , organic chemistry , evolutionary biology
Summary Soil acidity and waterlogging increase manganese (Mn) in leaf tissues to potentially toxic concentrations, an effect reportedly alleviated by increased silicon (Si) and phosphorus (P) supply. Effects of Si and P on Mn toxicity were studied in four plant species using synchrotron‐based micro X‐ray fluorescence (μ‐ XRF ) and nanoscale secondary ion mass spectrometry (Nano SIMS ) to determine Mn distribution in leaf tissues and using synchrotron‐based X‐ray absorption spectroscopy ( XAS ) to measure Mn speciation in leaves, stems and roots. A concentration of 30 μM Mn in solution was toxic to cowpea and soybean, with 400 μM Mn toxic to sunflower but not white lupin. Unexpectedly, μ‐ XRF analysis revealed that 1.4 mM Si in solution decreased Mn toxicity symptoms through increased Mn localization in leaf tissues. Nano SIMS showed Mn and Si co‐localized in the apoplast of soybean epidermal cells and basal cells of sunflower trichomes. Concomitantly, added Si decreased oxidation of Mn( II ) to Mn( III ) and Mn( IV ). An increase from 5 to 50 μM P in solution changed some Mn toxicity symptoms but had little effect on Mn distribution or speciation. We conclude that Si increases localized apoplastic sorption of Mn in cowpea, soybean and sunflower leaves thereby decreasing free Mn 2+ accumulation in the apoplast or cytoplasm.