Comparative understanding of metal hyperaccumulation in plants: a mini-review

Shvydkaya

et al. 2020

Plants

A biogeochemical study of more than 20,000 soil and plant samples from the North Caucasus, Dzungarian Alatau, Kazakh Uplands, and Karatau Mountains revealed features of the chemical element uptake by the local flora. Adaptation of ore prospecting techniques alongside environmental approaches allowed the detection of geochemical changes in ecosystems, and the lessons learned can be embraced for soil phytoremediation. The data on the influence of phytogeochemical stress on the accumulation of more than 20 chemical elements by plants are considered in geochemical provinces, secondary fields of deposits, halos surrounding ore and nonmetallic deposits, zones of regional faults and schist formation, and over lithological contact lines of chemically contrasting rocks overlain by 5–20 m thick soils and unconsolidated cover. We have corroborated the postulate that the element accumulation patterns of native plants under the natural geochemical stress depend not only on the element content in soils and the characteristics of a particular species but also on the values of ionic radii and valences; with an increase in the energy coefficients of a chemical element, its plant accumulation decreases sharply. The contribution of internal factors to element uptake from solutions gives the way to soil phytoremediation over vast contaminated areas. The use of hyperaccumulating species for mining site soil treatment depends on several external factors that can strengthen or weaken the stressful situation, viz., the amount of bedrock exposure and thickness of unconsolidated rocks over ores, the chemical composition of ores and primary halos in ore-containing strata, the landscape and geochemical features of sites, and chemical element migration patterns in the supergene zone.

Section: General Biogeochemical Accumulation Patternssupporting

confidence: 57%

Element Accumulation Patterns of Native Plant Species under the Natural Geochemical Stress

Shvydkaya

et al. 2020

Plants

“…(Brassicaceae) is a European pseudometallophyte that is known to hyperaccumulate trace elements (TEs) and is able to accumulate >20,000 mg Zn kg −1 , 2000 mg Cd kg −1 and 10,000 mg Ni kg −1 in its shoots. As a model species, it has considerably expanded our knowledge of metal hyperaccumulation and tolerance mechanisms (Assunção et al, 2018;Krämer, 2010;Peng et al, 2020;Verbruggen et al, 2018). Due to its abilities, N. caerulescens is also considered a promising candidate for field phytoextraction of Cd and/or Zn in moderately contaminated soils (Hammer and Keller, 2003;Jacobs et al, 2017Jacobs et al, , 2018aRosenfeld et al, 2018;Schwartz et al, 2003;Simmons et al, 2015;Sterckeman and Puschenreiter, 2018).…”

Section: Introductionmentioning

confidence: 99%

Dark septate endophytes isolated from non-hyperaccumulator plants can increase phytoextraction of Cd and Zn by the hyperaccumulator Noccaea caerulescens

Yung

Blaudez

Maurice

et al. 2021

Environ Sci Pollut Res

Dark septate endophytes (DSEs) can improve plant stress tolerance by promoting growth and affecting element accumulation. Due to its ability to accumulate high Cd, Zn and Ni concentrations in its shoots, Noccaea caerulescens is considered a promising candidate for phytoextraction in the field. However, the ability of DSEs to improve trace element (TE) phytoextraction with N. caerulescens has not yet been studied. The aim of this study was therefore to determine the ability of five DSE strains, previously isolated from poplar roots collected at different TE-contaminated sites, to improve plant development, mineral nutrient status and metal accumulation by N. caerulescens during a pot experiment using two soils differing in their level of TE contamination. Microscopic observations revealed that the tested DSE strains effectively colonized the roots of N. caerulescens. In the highly contaminated (HC) soil, a threefold increase in root biomass was found in plants inoculated with the Leptodontidium sp. Pr30 strain compared to that in the non-inoculated condition; however, the plant nutrient status was not affected. In contrast, the two strains Phialophora mustea Pr27 and Leptodontidium sp. Me07 had positive effects on the mineral nutrient status of plants without significantly modifying their biomass. Compared to non-inoculated plants cultivated on HC soil, Pr27-and Pr30-inoculated plants extracted more Zn (+30%) and Cd (+90%), respectively. In conclusion, we demonstrated that the responses of N. caerulescens to DSE inoculation ranged from neutral to beneficial and we identified two strains (i.e., Leptodontidium sp. (Pr30) and Phialophora mustea (Pr27)) isolated from poplar that appeared promising as they increased the amounts of Zn and Cd extracted by improving plant growth and/or TE accumulation by N. caerulescens. These results generate interest in further characterizing the DSEs that naturally colonize N. caerulescens and testing their ability to improve phytoextraction.

“…To cope with the above-mentioned toxicity, the plant initiates some defense mechanisms such as decreasing uptake and translocation of Cd, cell wall adsorption, and chelation and compartmentation [15,16]. In addition, the plant stimulates its enzymatic and non-enzymatic antioxidant defenses to scavenge ROS and mitigate Cd-induced oxidative stress [13,17].…”

Section: Introductionmentioning

confidence: 99%

Harnessing Endophytic Fungi for Enhancing Growth, Tolerance and Quality of Rose-Scented Geranium (Pelargonium graveolens (L’Hér) Thunb.) Plants under Cadmium Stress: A Biochemical Study

El-Shafey

Marzouk

Yasser

et al. 2021

JoF

Heavy metal contamination in soil is increasing rapidly due to increasing anthropogenic activities. Despite the importance of rose-scented geranium as a medicinal plant, little attention was paid to enhancing its productivity in heavy metal-polluted soil. In this regard, endophytes improve plant resistance to heavy metal toxicity and enhance its tissue quality. Here, the impact of the three endophytic fungi Talaromyces versatilis (E6651), Emericella nidulans (E6658), and Aspergillus niger (E6657) on geranium growth, tolerance, and tissue quality under cadmium (Cd) stress was investigated. In contrast to E. nidulans, T. versatilis and A. niger enhanced geranium growth and the stimulatory effect was more pronounced under Cd-stress. The three endophytes significantly alleviated Cd accumulation and increased mineral content in geranium leaves. In addition, endophytic fungi successfully alleviated Cd-induced membrane damage and reinforced the antioxidant defenses in geranium leaves. Inoculation with endophytes stimulated all the antioxidant enzymes under Cd-stress, and the response was more obvious in the case of T. versatilis and A. niger. To reduce the toxicity of tissue-Cd levels, T. versatilis and A. niger upregulated the detoxification mechanisms; glutathione-S-transferase, phytochelatin, and metallothionein levels. Moreover, endophytic fungi improved the medicinal value and quality of geranium by increasing total antioxidant capacity (TAC), phenolic compound biosynthesis (phenylalanine ammonia-lyase), and vitamin content as well as the quantity and quality of essential oil, particularly under Cd-stress conditions. The variation in the mechanisms modulated by the different endophytic fungi was supported by Principal Component Analysis (PCA). Overall, this study provided fundamental insights into endophytes’ impact as a feasible strategy to mitigate the phytotoxicity hazards of Cd-stress in geranium and enhance its quality, based on the growth and biochemical investigations.