Thinking for the future: Phytoextraction of cadmium using primed plants for sustainable soil clean‐up

Abstract

Cadmium (Cd) soil contamination is a global problem for food security due to its ubiquity, toxicity at low levels, persistence, and bioaccumulation in living organisms. Humans' intake of heavy metals is usually due to direct contact with contaminated soil, through the food chain (Cd accumulation in crops and edible plants) or through drinking water in cases of coupled groundwater‐surface water systems. Phytoextraction is one of the eco‐friendly, sustainable solutions that can be used as a method for soil clean‐up with the possibility of re‐use of extracted metals through phytomining. Phytoextraction is often limited by the tolerance level of hyperaccumulating plants and the restriction of their growth. Mechanisms of hyperaccumulation of heavy metals in tolerant species have been studied, but there are almost no data on mechanisms of further improvement of the accumulation capacity of such plants. Priming can influence plant stress tolerance by the initiation of mild stress cues resulting in acclimation of the plant. The potential of plant priming in abiotic stress tolerance has been extensively investigated using different types of molecules that are supplemented exogenously to plant organs (roots, leaves, etc.), resulting in enhanced tolerance of abiotic stress. This review focuses on mechanisms of enhancement of plant stress tolerance in hyperaccumulating plants for their exploitation in phytoextraction processes.

Epigenetics for crop adaptation to climate change

“…A third type involves bacterial strains (e.g., plant growth-promoting rhizobacteria, PGPR) to solubilize insoluble forms of Cd, enhance plant growth, or improve Cd uptake. Karalija et al (2022) emphasize the importance of priming, as epigenetic contributions have been firmly established and plants' stress tolerance is a major constraint of efficient phytoextraction. Alves et al (2022) performed an in silico study to identify gene sequences of epigenetic regulators in several tree species of the Fagaceae family with high economic and environmental interest.…”

“…The contributions of three epigenetic mechanisms (DNA methylation, histone post‐translational modifications, and enzymatic regulation) are also described and discussed. The reported studies aimed to describe how plants acclimate to abiotic environmental constraints (Alves et al, 2022), including low temperature and drought in early stages of winter wheat seedling establishment (Hidvégi et al, 2022), frost risks in budbreak and flowering stages of apple crops (Lempe et al, 2022), chronic heavy metal contamination in hyperaccumulating plants (Karalija et al, 2022) or flax (Jopčík et al, 2022) in the radioactive Chernobyl area, and biotic stresses such as powdery mildew caused by Plasmopara viticola in grapevine (Azevedo et al, 2022). Most also discussed the contributions of epigenetic regulations in acclimation processes or their evolution under continuous climate change generally, and/or in specific taxa, such as members of the Fagaceae family (Alves et al, 2022).…”

“…Overall, future directions have been proposed and discussed that indicate groundbreaking approaches that could promote the following: tolerance of powdery mildew caused by the biotrophic oomycete Plasmopara viticola in grapevine (Azevedo et al, 2022); acclimation to stressful conditions during sowing and seedling establishment in wheat (Hidvégi et al, 2022); phenological adjustment of budbreak and flowering in apple (Lempe et al, 2022); and adaptation to both chronic heavy metal contaminations (Jopčík et al, 2022; Karalija et al, 2022) and continuous climate change (Alves et al, 2022).…”

“…Abiotic constraints, at any time from early stages of crop establishment to late stages of fruit or grain development, also greatly reduce crop yields. To counter such losses, Hidvégi et al (2022) explored the effects of ultrasonication on wheat seeds to assess its potential value as a priming technique promoting seedling growth and Two articles in the special issue address the chronic contamination of soil by cadmium (Cd), one focused on flax growing in the Chernobyl area (Jopčík et al, 2022) and the other on "phytomining" approaches to extract Cd from contaminated soils (Karalija et al, 2022). Jopčík et al (2022) analyzed the genomes and epigenomes of sixth consecutive generations of flax plants growing in the radioactive Chernobyl area to measure the extent of their changes and whether they have led to plant adaptation nearly three decades after the Chernobyl nuclear power plant accident.…”

“…Two articles in the special issue address the chronic contamination of soil by cadmium (Cd), one focused on flax growing in the Chernobyl area (Jopčík et al, 2022) and the other on “phytomining” approaches to extract Cd from contaminated soils (Karalija et al, 2022). Jopčík et al (2022) analyzed the genomes and epigenomes of sixth consecutive generations of flax plants growing in the radioactive Chernobyl area to measure the extent of their changes and whether they have led to plant adaptation nearly three decades after the Chernobyl nuclear power plant accident.…”