Mercury Phytoremediation with Lolium perenne-Mycorrhizae in Contaminated Soils

Abstract

The symbiotic association between the roots of a plant and the mycelium of some fungi is identified as mycorrhizae. Symbiosis helps the plant to obtain nutrients from the soil more efficiently, and may favor the phytoremediation capacity of plants such as Lolium perenne, in soils contaminated with mercury. In this study, the morphological and molecular response was evaluated, as well as the variation in mercury accumulation in the different structures of L. perenne when associated with arbuscular mycorrhizal fungi. Association tests were performed to determine the optimal concentration of the biological inoculant and it was found that the best results were given with the proportion of one part of inoculant in three parts of soil (w/w ratio). The differential expression of the glutathione-S-transferase GST gene was evaluated through real-time PCR and the concentration of heavy metals inside and outside the plant was evaluated with inductively coupled plasma atomic emission spectroscopy (ICP). It was found that the plants that were inoculated with mycorrhizae developed longer stems and shorter roots; in the same way, the GST gene had greater expression in the stem than in the root, largely because the roots help the filtration of nutrients to the stem, retaining metals and detoxifying by GST-catalyzed glutathione.

Changes in Lolium perenne L. rhizosphere microbiome during phytoremediation of Cd- and Hg-contaminated soils

“…The “MICORRIZAR Biological Soil Inoculant” (AGROTECNIA LTDA, Bogotá, Colombia), which is roots colonized with a mixture of spores of the genera Glomus sp., Acaulospora sp., Entrophospora sp., and Giaspora sp. The association test was evaluated in previous work (Leudo et al 2020 ). The researcher found that this brand was the only ones that achieved an association with the root of the plants and the least amount of inoculant.…”

“…Four treatments were evaluated in duplicate according to previous studies (Cruz et al 2021(Cruz et al , 2019Leudo et al 2020).…”

“…Among these processes is phytoextraction, which is considered a commercial phytoremediation method with greater projection in the coming years (Zhao et al 2019). Studies on the remediation of metals such as Hg and Cd have focused on removal processes of these from plants (Cruz et al 2021(Cruz et al , 2019Leudo et al 2020). L. perenne (ryegrass) is a grass native to Europe, Asia, and North Africa and is now widely distributed throughout the world, including the Americas and Australia.…”

“…Some authors have verified its phytoremediation capacity of heavy metals individually of Cd and Hg (Cruz et al 2021(Cruz et al , 2019. On the other hand, studies have also been carried out in which this plant is placed in symbiosis with mycorrhizae, finding promising results in the elimination of Hg in soils (Leudo et al 2020). Regarding the molecular response, alterations of the GST gene have been observed, which is important because this gene encodes proteins that can help eliminate toxins from the plant (Cruz et al 2021).…”

Phytoremediation and Microorganisms-Assisted Phytoremediation of Mercury-Contaminated Soils: Challenges and Perspectives

“…Commercial arbuscular mycorrhizal formula, represented by Glomus, Entrophospora and Scutellospora genera, improved L. sativa seedlings development and promoted root elongation, even at 100 mg Hg kg −1 dw contaminated substrate, relative to uninoculated seedlings [ 171 ]. Commercial arbuscular mycorrhizal formulas associated with Lolium perenne , in soil containing 1 mg Hg 2+ kg −1 dw, resulted in higher root uptake (0.49 vs. 0.12 mg Hg kg −1 dw), lower translocation (0.28 vs. 0.75 mg Hg kg −1 dw), and lower overall metal removal from substrate (65.8%), compared to non-inoculated control (75.6%) [ 172 ]. Although these AMF inocula, which are non-indigenous to contaminated sites, stimulate plant growth and protect against Hg toxicity by reducing its bioavailability, metal removal is not achieved.…”