Potential of Grasses in Phytolith Production in Soils Contaminated with Cadmium

Fertilized soils enhance the efficiency of phytoremediation by tropical grasses in cadmium-contaminated soils

The effectiveness of phytoremediation in Cd-contaminated soils is crucial for enhancing nutrient availability and plant tolerance to Cd. We simulated soil contamination with varying textures and fertilization conditions. Two experiments were conducted: one without liming and fertilization and another with soil fertilization for grasses. The soil types used were Oxisol and Entisol, and the grasses tested were Megathyrsus maximus and Urochloa brizantha at three Cd levels: 0 mg kg-1 (Control), 2 mg kg-1 (Low), and 12 mg kg-1 (High). Soil amendments and fertilization did not significantly change Cd availability. Soil chemical attributes were unaffected by Cd contamination but were influenced by fertilization, which kept the pH below optimal levels. Cd availability was higher in more contaminated soils, with Entisol showing greater concentrations than Oxisol. Dry matter production of the grasses decreased with higher contamination, with U. brizantha being more productive than M. maximus in fertilized soils. Cd accumulation was higher in highly contaminated soils, particularly for U. brizantha. The bioconcentration factor was higher in Entisol, while the translocation factor exceeded 1.0 only for M. maximus in low-contamination Oxisol. Fertilization can mitigate Cd contamination effects, with U. brizantha showing greater tolerance and accumulation capacity in fertilized soils.

Silicon in Plants: Alleviation of Metal(loid) Toxicity and Consequential Perspectives for Phytoremediation

For the majority of higher plants, silicon (Si) is considered a beneficial element because of the various favorable effects of Si accumulation in plants that have been revealed, including the alleviation of metal(loid) toxicity. The accumulation of non-degradable metal(loid)s in the environment strongly increased in the last decades by intensified industrial and agricultural production with negative consequences for the environment and human health. Phytoremediation, i.e., the use of plants to extract and remove elemental pollutants from contaminated soils, has been commonly used for the restoration of metal(loid)-contaminated sites. In our viewpoint article, we briefly summarize the current knowledge of Si-mediated alleviation of metal(loid) toxicity in plants and the potential role of Si in the phytoremediation of soils contaminated with metal(loid)s. In this context, a special focus is on metal(loid) accumulation in (soil) phytoliths, i.e., relatively stable silica structures formed in plants. The accumulation of metal(loid)s in phytoliths might offer a promising pathway for the long-term sequestration of metal(loid)s in soils. As specific phytoliths might also represent an important carbon sink in soils, phytoliths might be a silver bullet in the mitigation of global change. Thus, the time is now to combine Si/phytolith and phytoremediation research. This will help us to merge the positive effects of Si accumulation in plants with the advantages of phytoremediation, which represents an economically feasible and environmentally friendly way to restore metal(loid)-contaminated sites.

The mechanism of silicon on alleviating cadmium toxicity in plants: A review

Cadmium is one of the most toxic heavy metal elements that seriously threaten food safety and agricultural production worldwide. Because of its high solubility, cadmium can easily enter plants, inhibiting plant growth and reducing crop yield. Therefore, finding a way to alleviate the inhibitory effects of cadmium on plant growth is critical. Silicon, the second most abundant element in the Earth's crust, has been widely reported to promote plant growth and alleviate cadmium toxicity. This review summarizes the recent progress made to elucidate how silicon mitigates cadmium toxicity in plants. We describe the role of silicon in reducing cadmium uptake and transport, improving plant mineral nutrient supply, regulating antioxidant systems and optimizing plant architecture. We also summarize in detail the regulation of plant water balance by silicon, and the role of this phenomenon in enhancing plant resistance to cadmium toxicity. An in-depth analysis of literature has been conducted to identify the current problems related to cadmium toxicity and to propose future research directions.

Effect of Soil Characteristics on Arsenic Accumulation in Phytolith of Gramineae (Phragmites japonica) and Fern (Thelypteris palustris) Near the Gilgok Gold Mine

In South Korea, most metal mines were abandoned and caused contamination for more than 30 years. Even the soil is highly contaminated with trace elements, plants still grow in the area and can affect the contamination. Phytolith is amorphous silica in the plant body. Phytolith is resistant to decomposition, and the stabilization of carbon, nutrients, and toxic substances accumulated in the phytolith is being studied. In this study, the Gilgok gold mine, which is contaminated with arsenic was selected as the research site. We selected Phragmites japonica and Thelypteris palustris as targets for the analysis of arsenic accumulation in plants and phytolith. Plants accumulate more phytolith at the riverside. The higher water content of soil increased the Arsenic (As) concentration in the frond of the T. palustris. Soil available silicon (Si) did not affect phytolith accumulation but increased As accumulation in the plant and phytolith. The research result showed that P. japonica and T. palustris have the ability to accumulate As in phytolith and the accumulation can be changed with soil characteristics and plant species. This As accumulation in phytolith can affect plant tolerance in contaminated areas and change the As availability in the soil. The result of the research can be used as a database to build a sustainable environment.

Identification and characterization of cadmium stress-related LncRNAs from Betula platyphylla

Cadmium (Cd) is one of the most serious global environmental pollutants, which inhibits plant growth and interferes with their physiological processes. However, there have been few studies on the involvement of long noncoding RNAs (lncRNAs) in Cd tolerance. In the present study, we identified the lncRNAs from Betula platyphylla (birch) that respond to Cd stress. Thirty lncRNAs that were differentially expressed under Cd treatment were identified, including 16 upregulated and 14 downregulated lncRNAs. Nine differentially regulated lncRNAs were selected for further characterization. These lncRNAs were transiently overexpressed in birch plants to determine their roles in Cd tolerance. Among them, two lncRNAs conferred Cd tolerance and two induced sensitivity to Cd stress. We further determined the Cd tolerance of four target genes of the lncRNAs involved in Cd tolerance, including l-lactate dehydrogenase A (LDHA),heat shock protein (HSP18.1), yellow stripe-like protein (YSL9), and H/ACA ribonucleoprotein complex subunit 2-like protein (HRCS2L). Among them, HSP18.1 and LDHA showed improved tolerance to Cd stress, whereas the other two genes did not appear to be involved in Cd tolerance. These results suggested that lncRNAs can up- or downregulate their target genes to improve Cd tolerance. These results increase our understanding of lncRNA-mediated Cd tolerance.