heavy-metal-toxicity
Heavy-metal toxicity occurs when plants take up excessive concentrations of metals such as cadmium, lead, arsenic, or mercury, along with essential micronutrients like copper and zinc at abnormally high levels, disrupting normal cellular function. This matters for plant science because metal accumulation can impair photosynthesis, root development, and enzyme activity, while also posing risks for food safety when toxic metals build up in edible tissues. Understanding the mechanisms of metal uptake, tolerance, and detoxification helps researchers develop crops that are more resilient to contaminated soils and safer for human consumption.
open_in_new WikipediaPubMed · 2026-06-30
Adding selenium to contaminated rice paddies cuts the amount of cadmium, arsenic, lead, and other toxic metals that rice grains absorb, by up to 54%. The mechanism turns out to be a chain reaction inside the root: selenium boosts a plant hormone that expands air channels in the root, which pumps oxygen into the soil, which triggers a rust-like iron coating on the root surface that traps the toxic metals before they can enter the plant.
Soil selenium amendment (1 mg/kg) reduced grain cadmium by 54%, arsenic by 34%, lead by 41%, chromium by 21%, nickel by 42%, and cobalt by 39% compared to untreated controls.
Selenium increased auxin (a plant growth hormone) levels by 2.74-fold, expanding root air-channel (aerenchyma) area from 34% to 65% of cortical cross-section.
Root surface iron plaque increased 5.64-fold under selenium treatment, with labile iron and manganese fluxes in the rhizosphere dropping by 54-89%, confirming that an oxidative iron barrier was responsible for blocking toxic metal uptake.
