Arsenic-phosphorus interactions in the soil-plant-microbe system: Dynamics of uptake, suppression and toxicity to plants

Abstract

High arsenic (As) concentrations in the soil, water and plant systems can pose a direct health risk to humans and ecosystems. Phosphate (Pi) ions strongly influence As availability in soil, its uptake and toxicity to plants. Better understanding of As(V)-Pi interactions in soils and plants will facilitate a potential remediation strategy for As contaminated soils, reducing As uptake by crop plants and toxicity to human populations via manipulation of soil Pi content. However, the As(V)-Pi interactions in soil-plant systems are complex, leading to contradictory findings among different studies. Therefore, this review investigates the role of soil type, soil properties, minerals, Pi levels in soil and plant, Pi transporters, mycorrhizal association and microbial activities on As-Pi interactions in soils and hydroponics, and uptake by plants, elucidate the key mechanisms, identify key knowledge gaps and recommend new research directions. Although Pi suppresses As uptake by plants in hydroponic systems, in soils it could either increase or decrease As availability and toxicity to plants depending on the soil types, properties and charge characteristics. In soil, As(V) availability is typically increased by the addition of Pi. At the root surface, the Pi transport system has high affinity for Pi over As(V). However, Pi concentration in plant influences the As transport from roots to shoots. Mycorrhizal association may reduce As uptake via a physiological shift to the mycorrhizal uptake pathway, which has a greater affinity for Pi over As(V) than the root epidermal uptake pathway.

Phosphate transporters, PnPht1;1 and PnPht1;2 from Panax notoginseng enhance phosphate and arsenate acquisition

“…Therefore, a high level of Pi supply to As-treated plants could decrease membrane damage by lowering oxidative injury [48]. In the plantation experiments, studies find that Pi supply could suppress As uptake by plants [26,[49][50][51], which is in line with our result as described in Figure S1. In addition, our results suggested that yeast cells expressing PnPht1;1 and PnPht1;2 improved As tolerance, particular in PnPht1;2 with a significant difference by comparison to MB192-vector, indicating by growth rate coefficients and the As tolerance index (Fig.…”

“…This finding suggests a competitive relationship of substrates between Pi and AsV [17,33,34]. However, the affinity of Pi or As with the Pi transporter depends on the characteristics of the Pi transporters, the concentration, the duration or chemical speciation of Pi and As, and the tissue of plants [19,26,[35][36][37]. In this study, qPCR results showed that upregulation of PnPht1;1 and PnPht1;2 expression is induced via either Pi deficiency or AsV exposure.…”

“…Suppression of AsV uptake is a common mechanism via supplementation with sufficient Pi due to the competition uptake between AsV and Pi [13,24]. Evidence suggested that AsV uptake was repressed by an increase in the Pi concentration, primarily due to the decline of Pht1's roles [25,26]. However, the alleviation of AsV uptake may be affected by upregulated expression of certain Pht1 genes [18,27,28], with the transporters exhibiting low affinity for AsV [13,29].…”

Influence of Soil Phosphate on the Accumulation and Toxicity of Arsenic and Antimony in Choy Sum Cultivated in Individually and Co‐contaminated Soils

“…Competition between PO 4 3− and AsO 4 3− at the plant root surface has been observed in a range of studies (Quaghebeur and Rengel 2004; Pigna et al 2009; Zhang et al 2017; Anawar et al 2018). Some studies have reported that these transporters had a greater affinity for PO 4 3− than AsO 4 3− (Pigna et al 2009; Anawar et al 2018). Xenidis et al (2010) showed that As uptake by dwarf beans increased with increasing soil PO 4 3− .…”

“…The oxyanions of P(V) and As(V) have tetrahedral structures and display very similar physical and chemical behaviors under aerobic environments (Strawn 2018). As a result, PO 4 3− and arsenate (AsO 4 3− ) compete for the same soil sorption sites, which can result in an increased As bioavailability (Anawar et al 2018). Some studies have shown that the presence of PO 4 3− in soil can partially decrease antimonite (SbO 4 3− ) adsorption on soil sorption sites and thereby increase Sb bioavailability in soil (Biver et al 2011; Xi et al 2011).…”