Germination of Bouteloua dactyloides and Cynodon dactylon in a Multi-Polluted Soil

Phytoremediation and Nurse Potential of Aloe Plants on Mine Tailings

Mine tailings are a source of potentially toxic metals (PTMs) worldwide. Phytoremediation is a low-cost green technology that uses metal-tolerant plants to extract these contaminants and rehabilitate the soil. In mine tailing restoration efforts, it can be beneficial to introduce species that can facilitate the colonization of other plants (i.e., nurse plant syndrome). In this study, the phytoremediation and nursing potential of two species adapted to metalliferous soil, Aloe burgersfortensis and A. castanea, were evaluated for the first time. An experiment was performed with aloe plants grown in pots containing potting soil, platinum tailings, and gold tailings. Leaves were assessed for bioaccumulation of PTMs. Seeds of Bermuda grass and African daisy, two successional pioneers, were planted with the aloes and had their developmental parameters evaluated after 30 days. Allelopathic effects were also assessed, with seeds of the pioneer plants infused with root extracts of the aloes from the different soil treatments. A. castanea demonstrated greater potential for the bioaccumulation of Cd, Co, Mn, Ni, and Zn in the tailings. The presence of aloes benefited germination rates, leaf count, length, and plant biomass of grasses and daisies in the mine tailings, without significant allelopathic effects. Therefore, aloes-especially A. castanea-should be employed in the rehabilitation of metal-contaminated soils to extract metals and to aid the establishment of other species to enhance the phytoremediation processes.

Application of Biochar for the Restoration of Metal(loid)s Contaminated Soils

Biochar has recently aroused great interest for the restoration of contaminated soils since it improves soil properties and induces the immobilization of pollutants. This study evaluates the use of biochar from plant pruning, applied as an amendment, for immobilizing metal(loid)s in a highly contaminated soil as well as for reducing the phytotoxicity of these pollutants by promoting natural revegetation. For this purpose, a bioassay with Trifolium pratense L. was used to test the effectiveness of the soil amendment in greenhouse conditions. Three treatments were carried out including soil contaminated with metal(loid)s (RA), and this soil was amended with biochar at different dosage: 4% (RA4B) and 8% (RA8B). A non-contaminated soil (NC) from a nearby area not affected by contamination was used as a control. The results show that biochar increased soil pH by several units depending on the dose used, 8% being the most effective one. Biochar treatments also reduced soluble and bioavailable forms of Zn and Cu. Likewise, phytotoxicity was significantly reduced, promoting seed germination and biomass with plant growth values similar to the non-polluted soil. In light of the results obtained, the evaluation of the bioremediation potential of biochar under field conditions can be considered.

Identifying Potential Planting Sites for Three Non-Native Plants to Be Used for Soil Rehabilitation in the Tula Watershed

The Tula watershed in Mexico, located in a semiarid and sub-humid climate zone, is experiencing intensive population growth, the expansion of mining concessions for construction materials, and agricultural and urban development, resulting in the degradation of soils and vegetation and a greater demand on natural resources. The aims of this study were to evaluate the survival rates and identify potential habitats within the Tula watershed for planting three non-native forage species (Atriplex canescens, Cynodon dactylon, and Leucaena collinsii) using the Kaplan-Meier estimator and the MaxEnt model with the purpose of rehabilitating degraded soils via agroforestry systems. There were 19 edaphoclimatic variables used and the occurrences of three species, obtained from the GBIF, MEXU, and SNIB databases. The models generated with MaxEnt were very accurate (area under the curve [AUC] ≥ 0.7). The species Atriplex canescens and Cynodon dactylon showed areas of potential planting sites (>0.4) and high survival rates (80% and 92%, respectively). The species Leucaena collinsii presented areas with lower potential planting (<0.4) but registered the greater survival rate (100%). The results provide a solid basis to evaluate the survival rates of forage species within potential planting sites in the Tula watershed using agroforestry systems to rehabilitate degraded soils.

Influence of a Helium–Nitrogen RF Plasma Jet on Onion Seed Germination

This paper presents an experiment using a radio frequency atmospheric pressure plasma jet to generate cold plasma for pre-sowing stimulation of Wolska onion seeds. Impact of the He + N2 afterglow plasma on germination was investigated. Eight groups of seeds characterized by different exposure times (2, 5, 10, 15, 60, 120, 240, and 480 s) and distance from the electrodes (20 mm and 50 mm) were used. Pre-sowing plasma stimulation of the seeds improved the germination capacity and germination energy for all tested groups, relative to control. The impact of radio frequency plasma on the onion seed germination parameters was statistically significant. The highest germination parameters were obtained for seeds stimulated for 240 s at a distance of 50 mm. No significant differences in physical and morphological properties of onion seeds were found.

Cadmium Hyperaccumulation and Translocation in Impatiens Glandulifera: From Foe to Friend?

The use of phytoremediation to sustainably recover areas contaminated by toxic heavy metals such as cadmium (Cd) has been made feasible since the discovery of hyperaccumulator plants. This study examines the potential of the invasive Impatiens glandulifera for phytoremediation propensity of Cd. In these experiments, the plants were exposed to and tested for Cd accumulation; the propensity to accumulate other heavy metals, such as Zinc, was not investigated. The efficacy of phytoaccumulation was assessed over two trials (Cd concentrations of 20 mg/kg to 150 mg/kg) via examination of bioconcentration factor (BCF), translocation factor (TF), and total removal (TR). Exposure to Cd levels of up to 150 mg/kg in the trials did not affect the biomass of the plants compared to the control. Impatiens glandulifera accumulated cadmium at a rate of 276 to 1562 mg/kgin stems, with BCFs, TFs, and TRs of 64.6 to 236.4, 0.2 to 1.2, and 3.6 to 29.2 mg Cd, respectively. In vitro germination revealed unprecedented germination ability, demonstrating the remarkable hypertolerance of I. glandulifera, with no significant difference in the germination of seedlings exposed to 1000 mg/kg Cd compared to the control. This study also examined the localization of Cd in plant tissues via a histochemical assay using dithizone. The results presented herein suggest that I. glandulifera can act as a hyperaccumulator of Cd for phytoremediation.

Analysis of native vegetation for detailed characterization of a soil contaminated by tannery waste

The risks for human health and the ecosystem due to potentially toxic elements (PTEs) were investigated in a farmland classified as potentially contaminated by Cr and Zn by analysing native vegetation and relative rhizo-soils. Rhizo-soils of different plant species were found to be enriched by Cr and Zn as well as by elements omitted from official environmental characterization, namely Cd, As and Pb. The ecological risk index (ERI) had a mean value of 510, indicating high to "very high" risk in different habitats. ERI above the very high risk threshold characterized the rhizo-soils of Lolium perenne, Erigeron sumatrensis, Oloptum thomasii and Amaranthus retroflexus. Two of these plant species (E. sumatrensis and A. retroflexus) are exotic in Italy and accumulated Cd in the shoots above the EU threshold for forage, suggesting a potential risk of Cd transfer to the food chain. Hence, this element was found to contribute most to the ERI. Cynodon dactylon was recognized as the most suitable plant species for the phytostabilization of the contaminated site, as it showed the highest bioavailable Cd accumulation in roots coupled with the highest frequency and soil-cover capacity during spring-summer, when the risk of soil resuspension is generally more intense.

Halophytic Grasses, a New Source of Nutraceuticals? A Review on Their Secondary Metabolites and Biological Activities

The Poaceae family, known as grasses, is distributed worldwide and is considered the most important group of monocotyledonous crops. Salt stress is multifactorial, therefore to survive, halophytes evolved a variety of adaptations, which include the biosynthesis of different primary and secondary metabolites. This trait enhances the accumulation of important families of compounds crucial to the prevention of a variety of chronic diseases. Besides, if proven edible, these species could cope with the increased soil salinity responsible for the decline of arable land due to their high nutritional/nutraceutical value. Herein, the phytochemical investigations performed in halophytes from the Poaceae family as well as their biological properties were explored. Among the 65 genera and 148 species of known halophytic grasses, only 14% of the taxa were studied phytochemically and 10% were subjected to biological evaluation. Notably, in the studied species, a variety of compound families, as well as bioactivities, were demonstrated, highlighting the potential of halophytic grasses.