ABSTRACT
In this study, we assessed the acute and chronic toxic effects of Sb (III) and Sb (V) on Eisenia fetida (Savingy) (E. fetida) by applying the filter paper contact method, aged soil treatment, and avoidance test experiment. In the acute filter paper contact test, the LC50 values for Sb (III) were 2581 mg/L (24 h), 1427 mg/L (48 h), and 666 mg/L (72 h), which were lower than Sb (V). In the chronic aged soil exposure experiment, when the Sb (III)-contaminated soil was aged 10 d, 30 d, and 60 d after exposure for 7 d, the LC50 value of E. fetida was 370, 613, and >4800 mg/kg, respectively. Compared to Sb (V) spiked soils aged only for 10 d, the concentrations causing 50% mortality significantly increased by 7.17-fold after 14 days of exposure in soil aged for 60 d. The results show that Sb (III) and Sb (V) could cause death and directly affect the avoidance behavior of E. fetida; yet, the toxicity of Sb (III) was higher than that of Sb (V). Consistent with the decrease in water-soluble Sb, the toxicity of Sb to E. fetida was greatly reduced with time. Therefore, in order to avoid overestimating the ecological risk of Sb with varying oxidative states, it is important to consider the forms and bioavailability of Sb. This study accumulated and supplemented the toxicity data, and provided a more comprehensive basis for the ecological risk assessment of Sb.
ABSTRACT
This study investigated an effective strategy for remediating antimony (Sb)-contaminated soil using the bacterial strain screened from Sb-contaminated fern rhizospheres due to its superior growth-promoting, heavy-metal(loid) resistant, and antibiotic-tolerant characteristics. The strain that belongs to Cupriavidus sp. was determined by 16S rRNA sequencing and showed no morphological changes when grown with high concentrations of Sb (608.8 mg/L). The strain showed prominent indole acetic acid (IAA), phosphate-solubilizing abilities, and ACC deaminase activity under Sb stress. Moreover, IAA and soluble phosphate levels increased in the presence of 608.8 mg/L Sb. Inoculation of rape seedlings with Cupriavidus sp. S-8-2 enhanced several morphological and biochemical growth features compared to untreated seedlings grown under Sb stress. Inoculation of Cupriavidus sp. S-8-2 increased root weight by more than four-fold for fresh weight and over two-fold for dry weight, despite high environmental Sb. The strain also reduced Sb-mediated oxidative stress and malondialdehyde contents by reducing Sb absorption, thus alleviating Sb-induced toxicity. Environmental Scanning Electron Microscope (ESEM) imaging and dilution plating technique revealed Cupriavidus sp. S-8-2 is localized on the surface of roots. Identifying the Sb-resistant plant growth-promoting bacterium suggested its usefulness in the remediation of contaminated agricultural soil and for the promotion of crop growth. We highly recommend the strain for further implementation in field experiments.
Subject(s)
Brassica napus , Cupriavidus , Antimony/toxicity , Seedlings , RNA, Ribosomal, 16S , PhosphatesABSTRACT
Antimony (Sb) is a dangerous heavy metal (HM) that poses a serious threat to the health of plants, animals, and humans. Leaching from mining wastes and weathering of sulfide ores are the major ways of introducing Sb into our soils and aquatic environments. Crops grown on Sb-contaminated soils are a major reason of Sb entry into humans by eating Sb-contaminated foods. Sb toxicity in plants reduces seed germination and root and shoot growth, and causes substantial reduction in plant growth and final productions. Moreover, Sb also induces chlorosis, causes damage to the photosynthetic apparatus, reduces membrane stability and nutrient uptake, and increases oxidative stress by increasing reactive oxygen species, thereby reducing plant growth and development. The threats induced by Sb toxicity and Sb concentration in soils are increasing day by day, which would be a major risk to crop production and human health. Additionally, the lack of appropriate measures regarding the remediation of Sb-contaminated soils will further intensify the current situation. Therefore, future research must be aimed at devising appropriate measures to mitigate the hazardous impacts of Sb toxicity on plants, humans, and the environment and to prevent the entry of Sb into our ecosystem. We have also described the various strategies to remediate Sb-contaminated soils to prevent its entry into the human food chain. Additionally, we also identified the various research gaps that must be addressed in future research programs. We believe that this review will help readers to develop the appropriate measures to minimize the toxic effects of Sb and its entry into our ecosystem. This will ensure the proper food production on Sb-contaminated soils.
ABSTRACT
Continued drought during the late growth stage of super hybrid rice (SHR) markedly reduces yield, and management practices that use water more efficiently can contribute greatly to high and stable yields from SHR. The absolute temperature differences (ATDs) between the rice plant and the atmosphere and between the soil and the atmosphere are believed to be important determinants of grain yield. However, it has not previously been determined whether these ATDs have any effect on SHR yields under water-saving cultivation. A two-year field experiment involving two SHR varieties, Liangyoupeijiu (LYPJ) and Y-Liangyou 9000 (YLY900), evaluated the effects of reducing water supply from mid-booting to maturity on grain yield, canopy relative humidity (CRH), leaf area index (LAI), and ATDs between the ambient temperature and the leaf surface, panicles, canopy, and soil. Grain yield increased significantly under shallow water irrigation (SW), by 8.84% (YLY900) and 12.26% (LYPJ), but decreased significantly under mild water stress (MS, -20 to -30 kPa), by 14.36% (YLY900) and 9.47% (LYPJ), as well as severe water stress (SS, -40 to -50 kPa), by 35.06% (YLY900) and 28.74% (LYPJ). As water supply decreased, so did the CRH and the ATDs, with significant decreases under MS and SS. The temperature differences were significantly and positively correlated with grain yield (P < 0.01) in both cultivars. LAI was increased under SW conditions, but was significantly decreased under MS and SS. Our study suggests that the dual goal of saving water while maintaining high yield can be achieved by applying SW irrigation from mid-booting to maturity and by adopting cultivation measures that maintain high CRH and high plant-atmosphere and soil-atmosphere ATDs in order to alleviate water stress. YLY900 has a higher yield potential than LYPJ under SW conditions, suggesting that its wide cultivation may help achieve this dual goal.
