The role of iron-rich organic fertilizer in promoting the growth of Chinese cabbage and inhibiting the transformation of cadmium

Synergistic effects of clays and cyanobacteria on the accumulation dynamics of soil organic carbon in artificial biocrusts

Biocrusts are the primary organic carbon reservoirs in desert areas, in which inorganic clays potentially playing significant roles; however, the specific details of these roles remain largely unclear. In this study, typical 1:1 type (kaolin) and 2:1 type (montmorillonite, MMT) clay minerals were added to artificial biocrusts to investigate their effect on the acquisition performance of soil organic carbon (SOC). After 84 days of cultivation, the enhancement effects of kaolin and MMT were significant, resulting in SOC increments that were 5.03 times and 4.08 times higher than those of the Algae group (without clay). Notably, the two types of clay exhibited different advantages in SOC accumulation. Due to its larger external specific surface area and higher cation exchange capacity, MMT contributes more effectively to SOC stability. Specifically, the mineralization quotient (qM), hot-water extractable organic carbon (HWEOC), and molecular structural stability of SOC in the MMT group were 0.3, 0.34, and 1.31 times those of the Algae group, respectively. In contrast, kaolin was more favorable for microbial growth and SOC formation due to its higher dissolved organic carbon (DOC) content. Microbial biomass carbon (MBC), chlorophyll-a (Chl-a), photosynthetic performance index (PIABS), and Shannon index in the kaolin group were 5.67, 2.44, 11.95, and 1.82 times those of the Algae group, respectively. These findings highlighted the synergistic effect for SOC accumulation of clay and cyanobacteria in artificial biocrust systems, clarified the specific roles of two typical clay minerals, and offered new insights for accelerating the restoration of nutrient-limited areas such as deserts.

Rice husk biochar resuscitates the microecological functions of heavy-metal contaminated soil after washing by enriching functional bacteria

Biochar has great potential for simultaneously improving soil ecological functions and eliminating environmental pollutants. However, studies on this strategy in the restoration of ecological functions in chelator-washed soil are lacking, and the effect of biochar on the structure, functions, and microbial interactions of washed soil microbiomes are unclear. Hence, the effect of rice husk biochar (RHB, 2 %) on the physicochemical properties, heavy metal fractions, and microbial community structure of glutamate-N, N-diacetic acid (GLDA)- and ethylenediaminetetraacetic acid (EDTA)- washed remediated soil were investigated. Results showed that the RHB addition restored the washed soil physical structure (pores and agglomerates) and meanwhile, the soil colloidal sheet sweeps increased by 20.49 % and 102.07 % in the z-axis, respectively. Additionally, RHB significantly increased washed soil pH (P < 0.05) and alkaline phosphatase and urease activities, while decreased acid phosphatase and glucosidase activities. The Observed-species and Shannon index were significantly higher in soil treated by RHB combined with GLDA and EDTA than those treated with GLDA and EDTA alone (P < 0.05). GLDA washing coupled RHB treatment enriched key bacterial groups such as MND1, Chelativorans, and Ellin6067, while EDTA washing coupled RHB treatment enriched Sreroidobacter, Micromonospora, and Reyranella, that both related to C-, N-, and P- cycles. Importantly, RHB addition could enrich functional bacteria by increasing bacterial resistance, including glucose metabolic homeostasis and metal ion resistance. The observed enrichment of functional bacteria provided evidence for the enhancement of soil nutrient cycles, indicative of improved soil functions by combination of chelator washing and biochar amended.

Invasive Amaranthus spp. for heavy metal phytoremediation: Investigations of cadmium and lead accumulation and soil microbial community in three zinc mining areas

Amaranthus spp. are a group of strongly invasive and vigorous plants, and heavy metal phytoremediation using alien invasive Amaranthus spp. has been a popular research topic. In this study, the bioconcentration factor (BCF) and translocation factor (TF) of Amaranthus spp. were evaluated, focusing on the accumulation potential of cadmium (Cd) and lead (Pb) by plants from three different zinc mining areas, namely Huayuan (HYX), Yueyang (LYX), and Liuyang (LYX). The HYX area has the most severe Cd contamination, while the LYX area has the most apparent Pb contamination. The results showed that Amaranthus spp. had a strong Cd and Pb enrichment capacity in low-polluted areas. To elucidate the underlying mechanisms, we used high-throughput sequencing of 16S rRNA and internal transcribed spacer (ITS) regions to analyze rhizosphere bacterial and fungal communities in three areas. The results showed significant differences in the structure, function, and composition of microbial communities and complex interactions between plants and their microbes. The correlation analysis revealed that some key microorganisms (e.g., Amycolatopsis, Bryobacterium, Sphingomonas, Flavobacterium, Agaricus, Nigrospora, Humicola) could regulate several soil factors such as soil pH, organic matter (OM), available nitrogen (AN), and available phosphorus (AP) to affect the heavy metal enrichment capacity of plants. Notably, some enzymes (e.g., P-type ATPases, Cysteine synthase, Catalase, Acid phosphatase) and genes (e.g., ZIP gene family, and ArsR, MerR, Fur, NikR transcription regulators) have been found to be involved in promoting Cd and Pb accumulation in Amaranthus spp. This study can provide new ideas for managing heavy metal-contaminated soils and new ways for the ecological resource utilization of invasive plants in phytoremediation.

Multivariate characterization of salicylic acid and potassium induced physio-biochemical and phytoremediation responses in quinoa exposed to lead and cadmium contamination

The levels of soils pollutants such as lead (Pb) and cadmium (Cd) have significantly increased recently resulting in ecological disturbances and threatening crop production. Various amendments have been employed to enhance the tolerance of crops to withstand Cd and Pb stresses. However, the role of combined application of potassium (K) and of salicylic acid (SA) for Cd and Pb stress mitigation and phytoremediation by quinoa (Chenopodium quinoa Willd) has not been comprehended well. In the present study, the effect of 10 mM K and 0.1 mM SA was tested on the quinoa plants subjected to 250 μM Pb and/or 100 μM Cd. The Pb and Cd treatments were applied separately or together. Phytotoxicity induced by Pb and Cd resulted in drastic decrease (>60%) in chlorophyll contents, stomatal conductance, and plant biomass. The collective treatment of Pb and Cd induced an increase in the concentration of hydrogen peroxide (13-fold) and lipid peroxidation (16-fold) that resulted in a 61% reduction in membrane stability. The application of 10 mM K and/or 0.1 mM SA was remarkable in mitigating the adverse effect of Pb and Cd. The reduction in plant biomass was 17% when 10 mM K and 0.1 mM SA were applied together under the combined treatment of both the metals. The simultaneous application of K and SA effectively mitigated oxidative stress by enhancing the activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase by 12, 10, 7 and 10-folds respectively. The positive effect of K and SA on these attributes resulted in a remarkable reduction in metal accumulation and translocation and lipid peroxidation. The stressed plants supplemented with K and SA exhibited a significant improvement in the membrane stability index, chlorophyll content, and stomatal conductance. This study concluded that the combined application of K and SA could be a good approach for reducing Pb and Cd phytotoxicity in quinoa and enhancing their phytostabilization potential in the contaminated soils.

Food Plants and Environmental Contamination: An Update

Food plants are the basis of human nutrition, but, in contaminated places, they can uptake contaminants. Environmental contamination and climate change can modify food quality; generally, they have a negative impact on and imply risks to human health. Heavy metals, like lead, arsenic, cadmium, and chromium, can be present at various environmental levels (soil, water, and atmosphere), and they are widely distributed in the world. Food plants can carry out heavy metal bioaccumulation, a defense pathway for plants, which is different for every plant species. Accumulation is frequent in the roots and the leaves, and heavy metals can be present in fruits and seeds; As and Cd are always present. In addition, other contaminants can bioaccumulate in food plants, including emerging contaminants, like persistent organic pollutants (POPs), pesticides, and microplastics. In food plants, these are present in the roots but also in the leaves and fruits, depending on their chemical structure. The literature published in recent years was examined to understand the distribution of contaminants among food plants. In the literature, old agronomical practices and new integrated technology to clean the water, control the soil, and monitor the crops have been proposed to mitigate contamination and produce high food quality and high food safety.

Promotion of rice seedlings growth and enhancement of cadmium immobilization under cadmium stress with two types of organic fertilizer

Cadmium (Cd)-contaminated soil poses a severe threat to crop production and human health, while also resulting in a waste of land resources. In this study, two types of organic fertilizer (ZCK: Low-content available iron; Z2: High-content available iron) were applied to Cd-contaminated soil for rice cultivation, and the effects of the fertilizer on rice growth and Cd passivation were investigated in conjunction with soil microbial analysis. Results showed that Z2 could alter the composition, structure, and diversity of microbial communities, as well as enhance the complexity and stability of the microbial network. Both 2% and 5% Z2 significantly increased the fresh weight and dry weight of rice plants while suppressing Cd absorption. The 2% Z2 exhibited the best Cd passivation effect. Gene predictions suggested that Z2 may promote plant growth by regulating microbial production of organic acids that dissolve phosphorus and potassium. Furthermore, it is suggested that Z2 may facilitate the absorption and immobilization of soil cadmium through the regulation of microbial cadmium efflux and uptake systems, as well as via the secretion of extracellular polysaccharides. In summary, Z2 can promote rice growth, suppress Cd absorption by rice, and passivate soil Cd by regulating soil microbial communities.

Insight into the soil bacterial community succession of Nicotiana benthamiana in response to Tobacco mosaic virus

Background

Tobacco mosaic virus (TMV) is one famous plant virus responsible for substantial economic losses worldwide. However, the roles of bacterial communities in response to TMV in the tobacco rhizosphere remain unclear.

Methods

We explored the soil physicochemical properties and bacterial community succession of the healthy (YTH) and diseased (YTD) plants with TMV infection by 16S rRNA gene sequencing and bioinformatics analysis.

Results

We found that soil pH in the YTD group was significantly lower than in the YTH group, and the soil available nutrients were substantially higher. The bacterial community analysis found that the diversity and structure significantly differed post-TMV disease onset. With TMV inoculated, the alpha diversity of the bacterial community in the YTD was markedly higher than that in the YTH group at the early stage. However, the alpha diversity in the YTD group subsequently decreased to lower than in the YTH group. The early bacterial structure of healthy plants exhibited higher susceptibility to TMV infection, whereas, in the subsequent stages, there was an enrichment of beneficial bacterial (e.g., Ramlibacter, Sphingomonas, Streptomyces, and Niastella) and enhanced energy metabolism and nucleotide metabolism in bacteria.

Conclusion

The initial soil bacterial community exhibited susceptibility to TMV infection, which might contribute to strengthening resistance of Tobacco to TMV.