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Interactions of the manganese hyperaccumulator Phytolacca americana L. with soil pH and phosphate
Author(s) -
DeGroote Kara V.,
McCartha Grace L.,
Pollard A. Joseph
Publication year - 2018
Publication title -
ecological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.628
H-Index - 68
eISSN - 1440-1703
pISSN - 0912-3814
DOI - 10.1007/s11284-017-1547-z
Subject(s) - hyperaccumulator , rhizosphere , phosphate , biology , botany , soil water , phytoremediation , phosphorus , manganese , environmental chemistry , birnessite , chemistry , ecology , biochemistry , manganese oxide , catalysis , organic chemistry , genetics , bacteria
Hyperaccumulators are plants that store exceptionally high concentrations of heavy metals or metalloids in their leaves. Phytolacca americana is one of the few species known to hyperaccumulate manganese (Mn); however, it is a common weedy species and has no specific association with high‐Mn soils. Neither the mechanism by which P . americana hyperaccumulates Mn nor the ecological significance of this trait are well understood. It has recently been suggested that P . americana secretes acids into the rhizosphere as a means of acquiring phosphate, which might coincidentally increase Mn uptake. To determine whether P . americana acidifies the surrounding soil, plants were grown in rhizoboxes providing access to living roots. A thin layer of agar containing bromocresol green pH indicator dye was placed on the roots to observe color changes indicating acidification. Comparative studies showed that P . americana acidifies the rhizosphere significantly more than the non‐accumulating plant Acalypha rhomboidea . A second experiment studied whether adjustment of soil pH and phosphate affect foliar Mn concentrations of P . americana . Concentrations of Mn in leaves were highest when plants were grown in acidified soils but were significantly lower in soils that were alkaline and/or enriched with phosphate. These results suggest that Mn hyperaccumulation may be a side effect of rhizosphere acidification as a phosphorus‐acquisition mechanism, rather than an adaptation in its own right. The findings provide fundamental information about hyperaccumulator physiology and evolution, and may be relevant to attempts to utilize P . americana for phytoremediation.