Arsenic and Phosphorus Transfer From Soils to Plants: Unique Ability of Arsenic Hyperaccumulator Pteris Vittata.

Arsenate, the most prevalent form of As in soils, is taken up by plant roots via phosphate (P_i) transporters.  However, labile P_i in soils is low and readily depleted by plant uptake.  To compensate, plants have evolved mechanisms to expedite P_i resupply, such as the production of finer roots, exudation of organic acid or acidification of the rhizosphere.  As-hyperaccumulator Pteris vittata L. (PV; Chinese brake fern) has the unparalleled ability to accumulate As from soils with low levels.  This suggests that the physiological aspects of P_i acquisition in PV are unique as P_i and As are chemical analogs.  In As-contaminated soils amended with phosphate rock (PR), a source of low available P_i, PV responded by increasing root biomass containing extensive root hair and adventitious growth, a trait absent in P_i-fertilized soils.  Pore water from the rhizosphere in PR-soils showed increased DOC (oxalic and malic acid) allowing PV to mineralize P_i from PR, even in alkaline soils, a unique observation.  Compared to growth with P_i-fertilizers, agronomic plants cannot adequately mineralize PR, suffering a reduction in biomass and yield.  Comparatively, PV biomass significantly increased in PR-soils in addition to accumulating more As compared to P_i-fertilized soils.  The rhizosphere modifications by PV in a P_i-limiting environment also mobilized As from fractions considered inaccessible for plant uptake.  In addition to providing a sustainable and affordable solution to As-contaminated soils, PV shows potential as a model plant for effective P_i acquisition and utilization.  Given the importance of P as a nonrenewable resource, understanding the P transfer in soil-rhizosphere-plant continuum may garner fundamental clues to develop crops that can efficiently acquire P from unavailable sources in soils.