[Response of Topsoil Fungal Community Structure to Soil Improvement Measures in Degraded Forest of Red Soil Region].

Soil fungal community structure and diversity are highly sensitive to variations in the external environment, as well as soil improvement measures. In order to clarify the effects of soil improvement measures on topsoil fertility or quality, a field experiment was conducted in eroded forest of a red soil region. Organic fertilizer, biochar, and lime+microbial fertilizer were added to the topsoil, respectively. After four years, the chemistry properties and nutrients in the topsoil were measured, and the diversity and composition of fungi were analyzed. The results showed that the additions of organic fertilizer, biochar, and lime+microbial fertilizer reduced fungal richness in topsoil, compared to that with no fertilizer addition (CK). Among them, lime+microbial fertilizer had the most negative effect on fungal richness. The three soil improvement measures also affected the diversity of topsoil fungi, but the impacts were not significant. The dominant fungal phyla in the topsoil were Ascomycota (31.29%-46.55%) and Basidiomycota (30.07%-70.71%), and the dominant fungal genera were Amphinema and Archaeorhizomyces. The effects of soil improvement measures on fungal community structure in the topsoil were different; organic fertilizer increased the relative abundance of Ascomycetes and Archaeopteroides, and biochar enhanced the relative abundance of Basidiomycetes and Archaeopteroides, whereas lime+microbial fertilizer improved the relative abundance of Basidiomycetes and Archaeopteroides. Fungal diversity and community structure in the topsoil was affected by edaphic factors, and fungal richness was regulated by pH value, whereas fungal community structure was influenced by pH, total nitrogen, and organic carbon. This study provides scientific guidance for soil improvement and ecological restoration below the canopy in eroded forests of red soil regions.

Effects of selenium on antioxidant enzyme activity and bioaccessibility of arsenic in arsenic-stressed radish.

Consuming arsenic (As)-contaminated vegetables is the main route of As exposure in humans. The present study focused on the alterations in antioxidant enzymatic activities and As bioaccessibility in As-contaminated radish subjected to Se. Compared to the CK group, the total As content in raw radish was reduced by 27.5 ± 1.3%, and the bioaccessibility of As was reduced by 21.9 ± 2.3% in the 6 mg Se kg-1 treatment group. The total As content in the treatment groups decreased first but then increased with increasing Se application in raw radish, gastric (G) fraction and gastrointestinal (GI) fraction, while the antioxidant activity exhibited the opposite trend. The results revealed that a low amount of Se effectively blocks the accumulation of As in radish, improves the antioxidant activity in radish and reduces the bioaccessibility of As. These findings provide new ideas for effectively alleviating the spread of As to the human body through the food chain.

Assessing bioaccessibility of Se and I in dual biofortified radish seedlings using simulated in vitro digestion.

Selenium (Se) and iodine (I) are essential elements for humans, and biofortification of vegetables with these elements is an effective way to amend their deficiencies in the diet. In this study, the distribution and transformation of Se and I species were investigated in radish seedlings that were simultaneously supplemented with these two elements; the fate and the bioaccessibility of Se and I species were dynamically surveyed in the oral, gastric and intestinal phases using a simulated in vitro digestion method. The radish seedlings were cultivated in hydroponic conditions with Se (IV), Se (VI), I- and IO3- (each 1 mg L-1). The results revealed that Se-methylselenocysteine (MeSeCys), selenocystine (SeCys2), selenomethionine (SeMet) and Se (VI) were present in radish, and MeSeCys was the dominant species in both gastric and intestinal extracts, comprising 32.7 ±â€¯1.5% and 39.6 ±â€¯1.1% of the total content, respectively. I- was also the dominant species, which accounted for 57.1 ±â€¯2.1%, 46.6 ±â€¯1.5% and 68.8 ±â€¯1.8% of the total digested content respectively in the oral, gastric and intestinal extracts. Meanwhile, IO3- was absent and organic I accounted for approximately 20%. The bioaccessibility of Se and I in the intestinal phase reached 95.5 ±â€¯2.5% and 85.8 ±â€¯0.9%, respectively; although after dialysis through membranes, the data reduced to 60.1 ±â€¯2.8% and 39.6 ±â€¯0.8%, respectively. Contents of MeSeCys and I- increased from the oral to intestinal phase and the bioaccessibility of both Se and I in radish was above 85%. So radish is suitable as a potential dietary source of Se and I with biofortification.

Estimation of arsenic bioaccessibility in raw and cooked radish using simulated in vitro digestion.

Consumption of arsenic (As)-contaminated vegetables is a major As exposure pathway for humans. However, little is known about plant As uptake characteristics and the bioaccessibility of As after ingestion of As-contaminated radish. The present study investigated As concentrations and species in As-contaminated radish and assessed the effects of steamed, griddled and boiled cooking on the bioaccessibility of As in radish using in vitro digestion. The results showed that the radish accumulated 46.3 ± 2.3, 79.2 ± 1.2 and 113.2 ± 3.7 µg As g-1 when treated with 0.5 mg L-1 As(iii) + 0.5 mg L-1 As(v), 1.0 mg L-1 As(iii) + 1.0 mg L-1 As(v) and 2.0 mg L-1 As(iii) + 2.0 mg L-1 As(v), respectively, in culture solution. In both gastric (G) and gastrointestinal (GI) fractions, the total As and species contents in radish decreased in the following order: raw > steamed > griddled > boiled. The bioaccessibility of total As was 97.5 ± 1.2%, 89.3 ± 1.3%, 84.8 ± 1.2% and 52.1 ± 1.1% in the GI phase when the radish was raw, steamed, griddled and boiled, respectively, and the bioaccessibility was not more than 60.1 ± 2.3% in the G phase. These data suggested that boiled cooking should be recommended for consumption of As-contaminated radish because it reduces total As and its species by approximately 50%. Additionally, organic As forms and factors influencing the bioaccessibility of As should be further studied to scientifically evaluate the health risks of As in radish.