Effects of oil contamination on plant growth and development: a review

Environmental risk substances in soil on seed germination: Chemical species, inhibition performance, and mechanisms

Nowadays, numerous environmental risk substances in soil worldwide have exhibited serious germination inhibition of crop seeds, posing a threat to food supply and security. This review provides a comprehensive summary and discussion of the inhibitory effects of environmental risk substances on seed germination, encompassing heavy metals, microplastics, petroleum hydrocarbons, salinity, phenols, essential oil, agricultural waste, antibiotics, etc. The impacts of species, concentrations, and particle sizes of various environmental risk substances are critically investigated. Furthermore, three primary inhibition mechanisms of environmental risk substances are elucidated: hindering water absorption, inducing oxidative damage, and damaging seed cells/organelles/cell membranes. To address these negative impacts, diverse effective coping measures such as biochar/compost addition, biological remediation, seed priming, coating, and genetic modification are proposed. In brief, this study systematically analyzes the negative effects of environmental risk substances on seed germination, and provides a basis for the comprehensive understanding and future implementation of efficient treatments to address this significant challenge and ensure food security and human survival.

Costus speciosus (Koen ex. Retz.) Sm.: a suitable plant species for remediation of crude oil and mercury-contaminated soil

The aim of this study was to evaluate the efficiency of Costus speciosus (Koen ex. Retz.) Sm. in the degradation of crude oil and reduction of mercury (Hg) from the contaminated soil in pot experiments in the net house for 180 days. C. speciosus was transplanted in soil containing 19150 mg kg-1 crude oil and 3.2 mg kg-1 Hg. The study includes the evaluation of plant biomass, height, root length, total petroleum hydrocarbon (TPH) degradation, and Hg reduction in soil, TPH, and Hg accumulation in plants grown in fertilized and unfertilized pots, chlorophyll production, and rhizospheric most probable number (MPN) at 60-day interval. The average biomass production and heights of C. speciosus in contaminated treatments were significantly (p < 0.05) lower compared to the unvegetated control. Plants grown in contaminated soil showed relatively reduced root surface area compared to the uncontaminated treatments. TPH degradation in planted fertilized, unplanted, and planted unfertilized pot was 63%, 0.8%, and 38%, respectively. However, compared to unvegetated treatments, TPH degradation was significantly higher (p < 0.05) in vegetated treatments. A comparison of fertilized and unfertilized soils showed that TPH accumulation in plant roots and shoots was relatively higher in fertilized soils. Hg degradation in soil was significantly (p < 0.05) more in planted treatment compared to unplanted treatments. The fertilized soil showed relatively more Hg degradation in soil and its accumulation in roots and shoots of plants in comparison to unfertilized soil. MPN in treatments with plants was significantly greater (p < 0.05) than without plants. The plant's ability to produce biomass, chlorophyll, break down crude oil, reduce Hg levels in soil, and accumulate TPH and Hg in roots and shoots of the plant all point to the possibility of using this plant to remove TPH and Hg from soil.

Sensitivity index for conservation priority ranking in the oil spill response: A case study for the coastal and marine species and habitat types in the Baltic Sea

Numerous anthropogenic stressors, such as habitat alteration and nutrient enrichment, affect coastal and marine ecosystems around the globe. An additional threat to these ecosystems is accidental oil pollution. The proactive planning of efficient oil spill response actions requires a firm understanding of the spatiotemporal distribution of ecological coastal values at stake, and how these values can be protected in case of an oil spill. In this paper, literature and expert knowledge regarding the life history attributes of coastal and marine species were used to build a sensitivity index to assess the differences in the potential of species and habitat types to be safeguarded from oil. The developed index prioritizes sensitive species and habitat types based on 1) their conservation value, 2) the oil-induced loss and recovery potential, and 3) the effectiveness of oil retention booms and protection sheets to safeguard these entities. The final sensitivity index compares the predicted difference in the state of populations and habitat types five years after an oil spill with and without protective actions. The higher the difference, the more worthwhile the management actions are. Hence, compared to other oil spill sensitivity and vulnerability indexes presented in the literature, the developed index considers the usefulness of protective measures explicitly. We apply the developed index to a case study area in the Northern Baltic Sea to demonstrate the approach. It is noteworthy that the developed index is applicable to other areas as well, as the approach is based on the biological attributes of species and habitat types instead of individual occurrences.

Characterization and genome analysis of Acinetobacter oleivorans S4 as an efficient hydrocarbon-degrading and plant-growth-promoting rhizobacterium

Plant-growth-promoting rhizobacteria (PGPR) have received increasing attention for assisting phytoremediation. However, the effect of PGPR on total petroleum hydrocarbon (TPH) degradation and plant growth promotion and its underlying mechanism is not well understood. In this study, phenotypic analysis and whole genome sequencing were conducted to comprehensively characterize a newly isolated rhizobacterium strain S4, which was identified as Acinetobacter oleivorans, from a TPH-contaminated soil. The strain degraded 62.5% of initially spiked diesel (1%) in minimal media within six days and utilized n-alkanes with a wide range of chain length (i.e., C₁₂ to C₄₀). In addition, the strain showed phenotypic traits beneficial to plant growth, including siderophore production, indole-3-acetic acid synthesis and phosphate solubilization. Potential metabolic pathways and genes encoding proteins responsible for the phenotypic traits were identified. In a real TPH-contaminated soil, inoculation of Acinetobacter oleivorans S4 significantly enhanced the growth of tall fescue relative to the soil without inoculation. In contrast, inoculation of Bacillus sp. Z7, a hydrocarbon-degrading strain, showed a negligible effect on the growth of tall fescue. The removal efficiency of TPH with inoculation of Acinetobacter oleivorans S4 was significantly higher than those without inoculation or inoculation of Bacillus sp. Z7. These results suggested that traits of PGPR beneficial to plant growth are critical to assist phytoremediation. Furthermore, heavy metal resistance genes and benzoate and phenol degradation genes were found in the genome of Acinetobacter oleivorans S4, suggesting its application potential in broad scenarios.

Evaluation of physicochemical parameters, acute and subchronic toxicities, and anti-diabetic activity of Spondias venulosa (Engl.) Mart. ex Engl. leaf extract on alloxan-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Spondias venulosa is a medicinal plant whose leaves are popularly used for decades in Northeast Nigeria as a first-choice medicinal plants for the treatment of diabetes. This claim has not been proven scientifically.

AIM OF THE STUDY

The present study was carried out to determine the physicochemical profiles, acute, sub-chronic toxicities, and antidiabetic activity the leaf extract in alloxan-induced diabetic rats.

MATERIALS AND METHODS

The physicochemical parameters of S. venulosa leaves, acute, subchronic toxicities, and antidiabetic activity in alloxan-induced diabetic rats were determined using standard procedures. All physicochemical parameters were carried out triplicate. Acute and subchronic toxicity studies were carried out following OECD guidelines by administering maximum extract dose of 2000 mg/kg orally to Wistar rats. Subchronic toxicity and antidiabetic studies were carried out in rats of opposite sexes at doses 300, 600, and 1200 mg/kg (orally).

RESULTS

Results obtained showed that the moisture content, water soluble extractive, and organic matter had values of 4.98 ± 1.01, 12.04 ± 1.24 and 1.01 ± 0.01% w/w respectively. The metallic contents of the methanol leaf extract revealed the presence of zinc with value of 12.01 ± 1.01 ppm (normal range:< 100 mg/kg DM) and copper with value of 6.24 ± 2.14 ppm (normal range:< 30 mg/kg DM). Oral median lethal dose (LD₅₀) was estimated to be greater than 2000 mg/kg since the extract did not produce any sign of toxicity or death in short term while, subchronic toxicity study showed that there was no significant weight loss in the rats after 28 days of extract administration. All hematology and biochemical parameters showed no elevated values when compared to the control group (p < 0.05). Histopathological examinations of major organs do not show signs of organ damages which indicate that the extract was safe at the doses administered. Oral administration of extract doses for 30 days reduced blood glucose levels in alloxan-induced diabetic rats in dose-dependent manner compared (p < 0.05) to standard drug (Glibenclamide).

CONCLUSIONS

Our study showed some physicochemical parameters of S. venulosa leaf which are essential for its identification from closely related species in traditional medicine. The study further showed that S. venulosa methanol leaf extract possessed antidiabetic activity, thus, justifying its use for the treatment of diabetes in Nigeria. However, there is need to identify and investigate the bioactive compound(s) responsible for the activity towards drug discovery.