Arsenic Uptake and Distribution in Green Pea Plants Under Arsenite and Arsenate Treatments

Soil arsenic (As) contamination is a global issue affecting regions worldwide. As in the soil is primarily present in inorganic forms, such as arsenite [As(III)] and arsenate [As(V)]. As is a microelement that is toxic to plants grown in As-contaminated soil. The aim of our study was to investigate the effects of increasing concentrations (0, 3, 10, 30, 90, and 270 mg kg⁻¹) of As(III) and As(V) on the As content in green pea (<i>Pisum sativum</i> L.) and the distribution of As among different plant parts at four phenophases (the four-node stage, beginning of flowering, green ripening, and mature stage). Another aim was to determine the percentage of total soil As available to plants under different treatments. The results indicate that the developmental stage of the pea and treatment concentration significantly influence the distribution of As among plant organs. However, the differences between the effect of inorganic As forms were less pronounced. The amount of As absorbed by the whole test plant increased with higher treatment concentrations. In the case of As(III)-treatment, As amount in the whole plant increased from 0.170 µg to 7.31 µg (I. Phenophase); from 0.294 µg to 10.1 µg (II. Phenophase); from 0.435 µg to 31.6 µg (III. Phenophase); and from 0.697 µg to 36.1 µg (IV. Phenophase). As a result of As(V)-treatment, the whole plant’s As content increased from 0.170 µg to 8.94 µg (I. Phenophase); from 0.294 µg to 17.4 µg (II. Phenophase); from 0.435 µg to 29.7 µg (III. Phenophase); and from 0.697 µg to 58.5 µg (IV. Phenophase). The concentration of As accumulated by the plant also increased over time. The proportion of As absorbed by generative parts was much smaller than that absorbed by vegetative organs. The pea seeds generally accumulated less As (maximum 7%) than the pea pods (in some cases, this reached the 10%). As the total amount of As taken up by the plant increased, the proportion of As reaching the seeds generally decreased (from 5% to 0.3% in the case of As[III]-treatment, and from 5% to 0.1% in the case of As[V]-treatment). At treatment levels where the ability of the stem to retain As increased, a maximum of 1% of the total As absorbed by the plant was found in the seeds. Depending on the treatment, 3.82–5.69% [As(V)-treatments] and 3.9–6.07% [As(III)-treatments] of the total soil As were available to the plants. The difference in the ratio of the total As content to the soluble As content was more evident at higher treatment levels (≥30 mg kg⁻¹). This value was typically lower for the As(V)-treatments.