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Phosphorus Stress-Induced Changes in Plant Root Exudation Could Potentially Facilitate Uranium Mobilization from Stable Mineral Forms
journal contribution
posted on 2018-05-03, 00:00 authored by Nimisha Edayilam, Dawn Montgomery, Brennan Ferguson, Amith S. Maroli, Nicole Martinez, Brian A. Powell, Nishanth TharayilApparent
deficiency of soil mineral nutrients often triggers specific
physio-morphological changes in plants, and some of these changes
could also inadvertently increase the ability of plants to mobilize
radionuclides from stable mineral forms. This work, through a series
of sand-culture, hydroponics, and batch-equilibration experiments,
investigated the differential ability of root exudates of Andropogon virginicus grown under conditions with variable
phosphorus (P) availability (KH2PO4, FePO4, Ca3(PO4)2, and no P) to
solubilize uranium (U) from the uranyl phosphate mineral Chernikovite.
The mineral form of P, and hence the bioavailability of P, affected
the overall composition of the root exudates. The lower bioavailable
forms of P (FePO4 and Ca3(PO4)2), but not the complete absence of P, resulted in a higher
abundance of root metabolites with chelating capacity at 72 hrs after
treatment application. In treatments with lower P-bioavailability,
the physiological amino acid concentration inside of the roots increased,
whereas the concentration of organic acids in the roots decreased
due to the active exudation. In batch dissolution experiments, the
organic acids, but not amino acids, increase the dissolution U from
Chernikovite. The root exudate matrix of plants exposed to low available
forms of P induced a >60% increase in U dissolution from Chernikovite
due to 5–16 times greater abundance of organic acids in these
treatments. However, this was ca. 70% of the theoretical dissolution
achievable by this exudate matrix. These results highlight the potential
of using active management of soil P as an effective tool to alter
the plant-mediated mobilization of U in contaminated soil.