| The arsenic (As) hyperaccumulating fern, Pteris vittata (Chinese brake fern), is capable of taking up arsenate (AsV) and arsenite (AsIII). The physiological aspects pertaining to the transformation of As in the media of the fern, its uptake mechanisms, speciation in the biomass and the impact of the hyperaccumulated arsenic on insects were studied.;The role of the fern and microbes in AsIII oxidation in the growth media and the location of AsIII oxidation and AsV reduction in P. vittata biomass were studied. Arsenic speciation was performed in the growth media, roots, rhizomes, rachis, pinnae, fronds, and sap of P. vittata . Arsenite was rapidly oxidized in the growth media by microbes and was then further oxidized in the roots of P. vittata. Arsenate reduction mostly occurred in the rhizomes and pinnae of P. vittata . Arsenite translocation from the roots to the fronds was more rapid than arsenate.;The mechanism of AsIII uptake was hypothesized to be via aquaporin transporters and was studied using competitors of AsIII uptake, glycerol and antimonite (SbIII), and also an inhibitor of aquaporin transporter, silver nitrate (AgNO 3). The presence of glycerol or SbIII had no impact on AsIII or AsV uptake by P. vittata. However, the presence of 0.01 mM AgNO 3 reduced the AsIII concentrations in the fronds and roots respectively, indicating that AsIII uptake might be via an aquaporin transporter different from the glycerol and SbIII transporters.;Arsenic hyperaccumulation by P. vittata may serve as a defense mechanism against herbivore attack. A study was conducted to examine the effects of arsenic concentrations on scale insect (Saissetia neglecta ) infestation of P. vittata. Scale insects were counted as percentage fallen from the plant to the total number of insects after 1 week of As-treatment. The higher arsenic concentrations in the fronds resulted in higher percentage of dead and fallen scale insects indicating that arsenic may help P. vittata defend against herbivore attack. |
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