Phytate and Arsenic Enhance Each Other’s Uptake in As-hyperaccumulator Pteris vittata: Root Exudation of Phytate and Phytase, and Plant Uptake of Phytate-P

Phytate as a root exudate is rare in plants as it mainly serves as a P storage in the seeds; however, As-hyperaccumulator Pteris vittataeffectively secretes phytate and utilizes phytate-P, especially under As exposure. This study investigated the effects of As on its phytate and phytase exudation and the impacts of As and/or phytate on each other’s uptake in P. vittatathrough two hydroponic experiments. Under 10–100 μM arsenate (AsV), the exudation of phytate and phytase by P. vittatawas increased by 50–72% to 20.4–23.4 μmol h–1g–1and by 28–104% to 18.6–29.5 nmol h–1plant–1, but they were undetected in non-hyperaccumulator Pteris ensiformisat 10 μM AsV. Furthermore, compared to 500 μM phytate, the phytate concentration in the growth media was reduced by 69% to 155 μM, whereas the P and As contents in P. vittatafronds and roots were enhanced by 68–134% and 44–81% to 2423–2954 and 82–407 mg kg–1under 500 μM phytate plus 50 μM AsV. The increased P/As uptake in P. vittatawas probably attributed to 3.0–4.5-fold increase in expressions of P transporters PvPht1;3–1;4. Besides, under As exposure, plant P may be converted to phytate in P. vittataroots, thereby increasing phytate’s contents by 84% to 840 mg kg–1. Overall, our results suggest that As-induced phytate/phytase exudation and phytate-P uptake stimulate its growth and As hyperaccumulation by P. vittata.