Removal of prometryn from hydroponic media using marsh pennywort (Hydrocotyle vulgaris L.)

The complete chloroplast genome sequence of Hydrocotyle vulgaris L. (Araliaceae)

Hydrocotyle vulgaris is a perennial wetland clonal plant in the Araliaceae family, which was introduced to China as an ornamental plant in the 1990s. Although H. vulgaris is now considered a potential invasiveness species in China, it also plays a significant role in the remediation of water pollution. Here, we reported its complete chloroplast genome and analyzed the basic characteristics. The chloroplast genome was 153,165 bp in length, including a pair of inverted repeat (IR) regions of 25,072 bp separated by a large single-copy (LSC) region of 84,291 bp and a small single-copy (SSC) region of 18,730 bp. The H. vulgaris chloroplast genome contained 132 predicted genes, and its overall GC content was 37.60%. Phylogenetic analysis revealed that H. vulgaris was closely related to H. verticillata. The H. vulgaris chloroplast genome presented in this study will lay a foundation for further genetic and genomic studies of the genus Hydrocotyle.

Co-contamination by heavy metal and organic pollutant alters impacts of genotypic richness on soil nutrients

Co-contamination by heavy metal and organic pollutant may negatively influence plant performance, and increasing the number of genotypes for a plant population may reduce this negative effect. To test this hypothesis, we constructed experimental populations of Hydrocotyle vulgaris consisting of single, four or eight genotypes in soils contaminated by cadmium, cypermethrin or both. Biomass, leaf area and stem internode length of H. vulgaris were significantly lower in the soil contaminated by cypermethrin and by both cadmium and cypermethrin than in the soil contaminated by cadmium only. A reverse pattern was found for specific internode length and specific leaf area. In general, genotypic richness or its interaction with soil contamination did not influence plant growth or morphology. However, soil nutrients varied in response to soil contamination and genotypic richness. Moreover, plant population growth was positively correlated to soil total nitrogen, but negatively correlated to total potassium and organic matter. We conclude that co-contamination by cadmium and cypermethrin may suppress the growth of H. vulgaris population compared to contamination by cadmium only, but genotypic richness may play little role in regulating these effects.

Use of cover crops in vineyards to prevent groundwater pollution by copper and organic fungicides. Soil column studies

Several fungicides, such as copper and organic products (synthetic or natural), are currently being used in vineyards to control downy mildew (Plasmopara viticola) resulting in soil, surface water, and groundwater pollution. This study aims to assess the effectiveness of using cover crops as an agricultural practice in vineyards to protect soil and groundwater pollution. For that purpose, we performed different soil column studies to quantify soil leaching of selected fungicides (copper, dimethomorph, oxathiapiprolin, zoxamide, acibenzolar-s-methyl, and laminarin) following a rainfall event after a conventional fungicide vineyard application. Two types of vineyard soils (loam and sandy-loam soil textures) and three ground covers (bare ground, monoculture cover, and polyculture cover) were assessed. These studies were completed with hydroponic assays to check the effectiveness of cover roots in the fungicide degradation. Mass balance results show that whereas 3 fungicides (Cu, zoxamide, and dimethomorph) were leached through sandy soil columns, only copper was leached from loam soil columns. The effect of cover crops was only significant for Cu and zoxamide when fungicides were applied 24 h before the rain event, reducing the fungicide leaching by 30%. Hydroponic studies showed that cover roots enhanced the kinetic rates of almost all tested fungicides by 5-467%, suggesting that they are relevant to improving the degradation of fungicides in the soil column. These results are relevant to drawing up recommendations on the use of cover crops to protect soil and groundwater pollution by fungicides.

Reviewing chemical and biological risks in urban agriculture: A comprehensive framework for a food safety assessment of city region food systems

Attention to urban agriculture (UA) has recently grown among practitioners, scientists, and the public, resulting in several initiatives worldwide. Despite the positive perception of modern UA and locally grown, fresh produce, the potential food safety risks connected to these practices may be underestimated, leading to regulatory gaps. Thus, there is a need for assessment tools to evaluate the food safety risks connected to specific UA initiatives, to assist practitioners in self-evaluation and control, and to provide policy makers and scholars a means to pursue and assess food safety in city regions, avoiding either a lack or an excess of regulation that could ultimately hinder the sector. To address this aim, this paper reviews the most recent and relevant literature on UA food safety assessments. Food safety indicators were identified first. Then, a food safety assessment framework for UA initiatives was developed. The framework uses business surveys and food analyses (if available) as a data source for calculating a food safety index for single UA businesses and the whole UA landscape of a given city region. The proposed framework was designed to allow its integration into the CRFS (City Region Food System) toolkit developed by FAO (Food and Agriculture Organization of the United Nations), RUAF foundation (Resource Centres on Urban Agriculture and Food Security) and Wilfrid Laurier University.

•

Connection of several biological and chemical food safety risks to UA techniques.

•

Identifiable food safety risk factors for diverse UA practices.

•

Framework for the assessment of food safety levels of UA initiatives.

•

Development of a risk-based assessment that can be integrated into the FAO CRFS framework.

Hydrocotyle vulgaris L.: a new cadmium-tolerant landscape species and its physiological responses to cadmium exposure

Landscape plants have both ecological and aesthetic value and may also represent ideal candidates for phytoremediation. In the present study, one round of hydroponic culture for 14 days with different cadmium (Cd) concentrations (0, 0.5, 1, and 2 mg L^-1 Cd) was carried out to test whether Hydrocotyle vulgaris L. is a Cd-tolerant plant. Furthermore, physiological parameters, including pigment concentrations, photosynthesis, antioxidant enzyme activities (AEAs), and nutrient uptake, were also examined to determine the tolerance of H. vulgaris to Cd exposure. The results showed that H. vulgaris could grow normally under all Cd supply levels. The Cd removal efficiency reached 100% at Cd concentrations ≤1.0 mg L^-1. The concentrations of Cd in roots and shoots increased (P < 0.05) with Cd supplementation. The maximum concentrations of Cd reached 26.4 and 118 mg kg^-1 in shoots and roots, respectively. The translocation factor values were similar under all Cd treatments. The highest mean daily increase in biomass (MDIB) was obtained under 1 mg L^-1 Cd exposure, which increased by 69.86% compared to that in the control, which may be due to the increased photosynthetic pigments, photosynthetic rate, and the consistent nutrient concentrations under this Cd level, as there were positive relationships between these parameters and MDIB. Moreover, the activities of AEA also generally explicated highest among all Cd levels. All these results indicate that the above physiological parameters play a positive role in promoting plant growth and alleviating Cd stress. In summary, H. vulgaris was verified as a potential Cd-tolerant plant, providing new information for Cd phytoremediation. Furthermore, given its extensive habitat distribution, this species might be tested for phytoremediation of contaminated soils in future work.

Toxicity, uptake and transport mechanisms of dual-modal polymer dots in penny grass (Hydrocotyle vulgaris L.)

The use of polymers such as plastic has become an important part of daily life, and in aqueous environments, these polymers are considered as pollutants. When macropolymers are reduced to the nanoscale, their small particle size and large specific surface area facilitate their uptake by plants, which has a significant impact on aquatic plants. Therefore, it is essential to study the pollution of nanoscale polymers in the aquatic environment. In this work, we prepared nanoscale polymer dots (Pdots) and explored their toxicity, uptake and transport mechanisms in penny grass. From toxicological studies, in the absence of other nutrients, the cell structure, physiological parameters (total soluble protein and chlorophyll) and biochemical parameters (malondialdehyde) do not show significant changes over at least five days. Through in vivo fluorescence and photoacoustic (PA) imaging, the transport location can be visually detected accurately, and the transport rate can be analyzed without destroying the plants. Moreover, through ex vivo fluorescence imaging, we found that different types of Pdots have various uptake and transport mechanisms in stems and blades. It may be due to the differences in ligands, particle sizes, and oil-water partition coefficients of Pdots. By understanding how Pdots interact with plants, a corresponding method can be developed to prevent them from entering plants, thus avoiding the toxicity from accumulation. Therefore, the results of this study also provide the basis for subsequent prevention work.