Improvements in the biochemical responses and Pb and Ni phytoremediation of lavender (Lavandula angustifolia L.) plants through Funneliformis mosseae inoculation

Mitigating pb toxicity in Sesbania sesban L. through activated charcoal supplementation: a hydroponic study on enhanced phytoremediation

BACKGROUND

Soil contamination by heavy metals is a critical environmental challenge, with Pb being of particular concern due to its propensity to be readily absorbed and accumulated by plants, despite its lack of essential biological functions or beneficial roles in cellular metabolism. Within the scope of phytoremediation, the use of plants for the decontamination of various environmental matrices, the present study investigated the potential of activated charcoal (AC) to enhance the tolerance and mitigation capacity of S. sesban seedlings when exposed to Pb. The experiment was conducted as a factorial arrangement in a completely randomized design in hydroponic conditions. The S. sesban seedlings were subjected to a gradient of Pb concentrations (0, 0.02, 0.2, 2, and 10 mg/L) within the nutrient solution, alongside two distinct AC treatments (0 and 1% inclusion in the culture media). The study reached its conclusion after 60 days.

RESULTS

The seedlings exposed to Pb without AC supplementation indicated an escalation in peroxidase (POX) activity, reactive oxygen species (ROS), and malondialdehyde (MDA) levels, signaling an increase in oxidative stress. Conversely, the incorporation of AC into the treatment regime markedly bolstered the antioxidative defense system, as evidenced by the significant elevation in antioxidant capacity and a concomitant reduction in the biomarkers of oxidative stress (POX, ROS, and MDA).

CONCLUSIONS

With AC application, a notable improvement was observed in the chlorophyll a, total chlorophyll, and plant fresh and dry biomass. These findings illuminate the role of activated charcoal as a viable adjunct in phytoremediation strategies aimed at ameliorating heavy metal stress in plants.

Mycorrhizae in mine wasteland reclamation

Mycorrhizae are found on about 70-80 % of the roots of all plant species; ectomycorrhizae (ECM) are mostly found on woody plants and gymnosperms, whereas arbuscular mycorrhizal fungi (AMF) are found on 80-90 % of all plant species. In abandoned mining sites, woody plants dominate, while non-woody species remain scarce. However, this pattern depends on the specific mine site and its ecological context. This review article explores the potential of using mycorrhizae-plant associations to enhance and facilitate the remediation of mine wastelands and metal-polluted sites. In this review, we employed reputable databases to collect articles and relevant information on mycorrhizae and their role in plant growth and soil fertility spanning from the 1990s up to 2024. Our review found that the abilities of plants selected for minewasteland reclamation can be harnessed effectively if their mycorrhizae utilization is known and considered. Our findings indicate that AMF facilitates plant cohabitation by influencing species richness, feedback effects, shared mycelial networks, and plant-AMF specificity. Several types of mycorrhizae have been isolated from mine wastelands, including Glomus mosseae, which reduces heavy metal accumulation in plants, and Rhizophagus irregularis, which enhances plant growth and survival in revegetated mine sites. Additionally, studies on ECM in surface mine spoil restoration stands highlight their role in enhancing fungal biodiversity and providing habitats for rare and specialized fungal species. Recent research shows that ECM and AMF fungi can interact synergistically to enhance plant growth, with ECM improving plant nitrogen absorption and AMF increasing nitrogen use efficiency. Our review also found that despite their critical role in improving plant growth and resilience, there remains limited knowledge about the specific mechanisms by which mycorrhizae communicate with each other and other microorganisms, such as bacteria, root-associated fungi, soil protozoa, actinomycetes, nematodes, and endophytes, within the soil matrix. This article highlights the connection between mycorrhizae and plants and other microorganisms in mine wastelands, their role in improving soil structure and nutrient cycling, and how mycorrhizae can help restore soil fertility and promote plant growth, thus improving the overall environmental quality of mine wasteland sites.

Arbuscular Mycorrhizal Fungi-Mediated Modulation of Physiological, Biochemical, and Secondary Metabolite Responses in Hemp (Cannabis sativa L.) under Salt and Drought Stress

The increasing impact of global climate change has resulted in adversity stresses, like salt and drought, gradually becoming the main factors that limit crop growth. Hemp, which contains numerous medicinal active components and multiple bioactive functions, is widely used in the agricultural, industrial, and medical fields, hence promoting the rapid development of related industries. Arbuscular mycorrhizal fungi (AMF) can establish a symbiotic relationship with 80% of vascular plants. This symbiosis promotes host plant growth, regulates plant physiology and biochemistry, facilitates secondary metabolite synthesis, and enhances resistance to abiotic stresses. However, the effects of salt stress, drought stress, and AMF interaction in hemp are not well understood. In this study, to investigate this, we performed a study where we cultured hemp that was either inoculated or uninoculated with Funneliformis mosseae and determined changes in effective colonization rate, growth, soluble substances, photosynthesis, fluorescence, ions, and secondary metabolites by cultivating hemp under different concentrations of NaCl (0 mM, 100 mM, and 200 mM) and different soil moisture content (45%, 25%, and 15%). The results showed that salt, drought stress, or salt-drought interaction stress all inhibited colonization rate after stress, plant growth, mainly due to ion toxicity and oxidative damage. Inoculation with F. mosseae effectively alleviated plant growth inhibition under 100 mM NaCl salt stress, drought stress, and salt-drought interaction stress conditions. It also improved osmoregulation, photosynthetic properties, fluorescence properties, and ion homeostasis, and promoted the accumulation of secondary metabolites. However, under 200 mM NaCl salt stress conditions, inoculation with F. mosseae negatively affected plant physiology, biochemistry, and secondary metabolite synthesis, although it did alleviate growth inhibition. The results demonstrate that there are different effects of salt-drought interaction stress versus single stress (salt or drought stress) on plant growth physiology. In addition, we provide new insights about the positive effects of AMF on host plants under such stress conditions and the effects of AMF on plants under high salt stress.

Synergistic interactions of assorted ameliorating agents to enhance the potential of heavy metal phytoremediation

Pollution by toxic heavy metals creates a significant impact on the biotic community of the ecosystem. Nowadays, a solution to this problem is an eco-friendly approach like phytoremediation, in which plants are used to ameliorate heavy metals. In addition, various amendments are used to enhance the potential of heavy metal phytoremediation. Symbiotic microorganisms such as phosphate-solubilizing bacteria (PSB), endophytes, mycorrhiza and plant growth-promoting rhizobacteria (PGPR) play a significant role in the improvement of heavy metal phytoremediation potential along with promoting the growth of plants that are grown in contaminated environments. Various chemical chelators (Indole 3-acetic acid, ethylene diamine tetra acetic acid, ethylene glycol tetra acetic acid, ethylenediamine-N, N-disuccinic acid and nitrilotri-acetic acid) and their combined action with other agents also contribute to heavy metal phytoremediation enhancement. With modern techniques, transgenic plants and microorganisms are developed to open up an alternative strategy for phytoremediation. Genomics, proteomics, transcriptomics and metabolomics are widely used novel approaches to develop competent phytoremediators. This review accounts for the synergistic interactions of the ameliorating agent's role in enhancing heavy metal phytoremediation, intending to highlight the importance of these various approaches in reducing heavy metal pollution.

Glycine-Rich RNA-Binding Protein AtGRP7 Functions in Nickel and Lead Tolerance in Arabidopsis

Plant glycine-rich RNA-binding proteins (GRPs) play crucial roles in the response to environmental stresses. However, the functions of AtGRP7 in plants under heavy metal stress remain unclear. In the present study, in Arabidopsis, the transcript level of AtGRP7 was markedly increased by Ni but was decreased by Pb. AtGRP7-overexpressing plants improved Ni tolerance, whereas the knockout mutant (grp7) was more susceptible than the wild type to Ni. In addition, grp7 showed greatly enhanced Pb tolerance, whereas overexpression lines showed high Pb sensitivity. Ni accumulation was reduced in overexpression lines but increased in grp7, whereas Pb accumulation in grp7 was lower than that in overexpression lines. Ni induced glutathione synthase genes GS1 and GS2 in overexpression lines, whereas Pb increased metallothionein genes MT4a and MT4b and phytochelatin synthase genes PCS1 and PCS2 in grp7. Furthermore, Ni increased CuSOD1 and GR1 in grp7, whereas Pb significantly induced FeSOD1 and FeSOD2 in overexpression lines. The mRNA stability of GS2 and PCS1 was directly regulated by AtGRP7 under Ni and Pb, respectively. Collectively, these results indicate that AtGRP7 plays a crucial role in Ni and Pb tolerance by reducing Ni and Pb accumulation and the direct or indirect post-transcriptional regulation of genes related to heavy metal chelators and antioxidant enzymes.

Growth and Primary Metabolism of Lettuce Seedlings (Lactuca sativa L.) Are Promoted by an Innovative Iron-Based Fenton-Composted Amendment

Information regarding the physiological and molecular plant responses to the treatment with new biofertilizers is limited. In this study, a fast-composting soil amendment obtained from solid waste by means of a Fenton reaction was assessed to evaluate the effects on the growth of Lactuca sativa L. var. longifolia seedlings. Growth rate, root biomass, chlorophyll concentration, and total soluble proteins of seedlings treated with the 2% fast-composting soil amendment showed significant increases in comparison with the control seedlings. Proteomic analysis revealed that the soil amendment induced the up-regulation of proteins belonging to photosynthesis machinery, carbohydrate metabolism, and promoted energy metabolism. Root proteomics indicated that the fast-composting soil amendment strongly induced the organs morphogenesis and development; root cap development, lateral root formation, and post-embryonic root morphogenesis were the main biological processes enriched by the treatment. Overall, our data suggest that the addition of the fast-composting soil amendment formulation to the base soils might ameliorate plant growth by inducing carbohydrate primary metabolism and the differentiation of a robust root system.