P Accumulation and Root Responses to Different High P Regimes in Polygonum hydropiper for Understanding a P-phytoremediation Strategy

Phosphorus (P) accumulators used for phytoremediation vary in their potential to acquire P from different high P regimes. Growth and P accumulation in Polygonum hydropiper were both dependent on increasing levels of phytate-P (1-8 mM P) and on various P sources. The mining ecotype (ME) showed higher biomass and P accumulation than the non-mining ecotype (NME) under different high phytate-P treatments. Biomass increments in root, stem, and leaf of both ecotypes were significantly greater in phytate-P relative to other organic P (Po) sources (G1P, AMP, ATP), but lower than those in inorganic P (Pi) treatment (KH₂PO₄). P accumulation in the ME exceeded the NME from different P regimes. Seedlings fed with phytate-P demonstrated significantly greater morphological parameters of fine, medium and thick roots compared to other Po sources. The ME has a higher ability to develop root system and exhibits better distribution of fine roots to enhance P accumulation from high P media. Higher root activity was observed in the ME than the NME grown in various P sources. Acid phosphatase (Apase) and phytase activities in root extracts of both ecotypes grown in phytate-P were comparable to that in Pi, or even higher in phytate-P treatment. Higher secreted Apase and phytase activities were detected in the ME treated with different P sources relative to the NME. Therefore, the ME demonstrates higher P-uptake ability and it is a potential material for phytoextraction from P contaminated areas, irrespective of Pi or Po contamination.