Root physiological adaptations involved in enhancing P assimilation in mining and non-mining ecotypes of Polygonum hydropiper grown under organic P media.

Daihua Ye,Tingxuan Li,Guangdeng Chen,Haiying Yu,Zicheng Zheng,Xizhou Zhang

doi:10.3389/fpls.2015.00036

Abstract

It is important to seek out plant species, high in phosphorus (P) uptake, for phytoremediation of P-enriched environments with a large amount of organic P (Po). P assimilation characteristics and the related mechanisms of Polygonum hydropiper were investigated in hydroponic media containing various concentrations of Po (1–8 mmol L-1) supplied as phytate. The mining ecotype (ME) showed significantly higher biomass in both shoots and roots compared to the non-mining ecotype (NME) at 4, 6, and 8 m mol L-1. Shoot P content of both ecotypes increased up to 4 mmol L-1 while root P content increased continually up to 8 mmol L-1 for the ME and up to 6 mmol L-1 for the NME. Root P content of the ME exceeded 1% dry weight under 6 and 8 mmol L-1. The ME had significantly higher P accumulation in both shoots and roots compared to the NME supplied with 6 and 8 mmol L-1. The ME showed higher total root length, specific root length, root surface area, root volume, and displayed significantly greater root length, root surface area, and root volume of lateral roots compared to the NME grown in all Po treatments. Average diameter of lateral roots was 0.17–19 mm for the ME and 0.18–0.21 mm for the NME. Greater acid phosphatase and phytase activities were observed in the ME grown under different levels of Po relative to the NME. This indicated fine root morphology, enhanced acid phosphatase and phytase activities might be adaptations to high Po media. Results from this study establish that the ME of P. hydropiper is capable of assimilating P from Po media and is a potential material for phytoremediation of polluted area with high Po.

Highlights

Soils contain an enormous amount of phosphorus (P), commonly the bulk of which is fixed into organic P (Po) depending on land use, location, and soil type (Kong et al, 2014; Nash et al, 2014)
No significant difference in root biomass was noticed in the mining ecotype (ME), whereas the non-mining ecotype (NME) exhibited a persistent decrease in various concentrations of Po (Figure 1B)
In the two ecotypes of P. hydropiper, the ME seems to be more tolerant to various concentrations of Po and exhibited greater biomass, tissue P content, bioaccumulation coefficient (BCF) compared to the NME

Summary

Introduction

Soils contain an enormous amount of phosphorus (P), commonly the bulk (greater than 50%) of which is fixed into organic P (Po) depending on land use, location, and soil type (Kong et al, 2014; Nash et al, 2014). Inositol phosphates belonging to orthophosphate monoesters, phytate (inositol hexaphosphate), and its metal ion compounds, are the most abundant forms of soil Po (Turner et al, 2002; Condron et al, 2005). To satisfy plant requirements for available P, substantial P-based fertilizers (e.g., chemical fertilizer and animal manure) are used in many agricultural production systems (Pant et al, 2004; Nash et al, 2014). The excreted manure contains a large number of undigested feed phytate, which leads to redistribution of Po (Priya and Sahi, 2009) and accumulation of total P in soils. The potential environmental pollution caused by phytate arising from long-term and iterative applications of P-based fertilizers and arbitrary emission of animal manure should be addressed

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Conclusion