The toxicological effect on pak choi of co-exposure to degradable and non-degradable microplastics with oxytetracycline in the soil.

Microplastics and antibiotics are emerging as ubiquitous contaminants in farmland soil, harming crop quality and yield, and thus threatening global food security and human health. However, few studies have examined the individual and joint effects of degradable and/or non-degradable microplastics and antibiotics on crop plants. This study examined the individual and joint effects of polyethylene (PE) and polylactic acid (PLA) microplastics and the antibiotic oxytetracycline (OTC) on pak choi by measuring its growth, photosynthesis, antioxidant enzyme activity, and metabolite levels. Microplastics and/or oxytetracycline adversely affected root weight, photosynthesis, and antioxidant enzyme (superoxide dismutase, catalase, and ascorbate peroxidase) activities. The levels of leaf metabolites were significantly altered, causing physiological changes. Biosynthesis of plant secondary metabolites and amino acids was altered, and plant hormones pathways were disrupted. Separately and together, OTC, PE, and PLA exerted phytotoxic and antagonistic effects on pak choi. Separately and together with OTC, degradable microplastics altered the soil properties, thus causing more severe impacts on plant performance than non-degradable microplastics. This study elucidates the effects on crop plants of toxicity caused by co-exposure to degradable or non-degradable microplastic and antibiotics contamination and suggests mechanisms.

Impact of polystyrene microplastics with combined contamination of norfloxacin and sulfadiazine on Chrysanthemum coronarium L.

Antibiotics and microplastics including nanoplastics are emerging contaminants which have become global environmental issues. The application of antibiotics along with microplastics in soil and their entrance in food chain may pose a major threat to human health. The single and combined exposure of polystyrene microplastic (MPS), norfloxacin (NF) and sulfadiazine (SFD) on Chrysanthemum coronarium L. a medicinal food crop, were investigated. Accumulation of nutrient element contents (Fe, Mn, Mg, Zn, K) differentially responded to the single or combined treatments compared to the control. Scanning electron microscopy and transmission electron microscopy analysis indicated that MPS, NF and SFD accumulated in roots, shoots, and leaves and affected their ultrastructure. Compared with that of the single contamination, the co-contamination of microplastics and antibiotics had a greater effect on leaf metabolites due to combination of multiple abiotic stresses. MPS, NF and SFD accumulated from roots and transported to shoots and leaves which ultimately impacts plant metabolites and, nutritional value. They subsequently impact agricultural sustainability and food safety of medicinal food plants. This investigation suggests the possible ecological risks of microplastics to medicinal food plants, especially in co-exposure with organic pollutants like antibiotics and help to reveal potential mechanisms of phytotoxicity of different antibiotics with polyethylene microplastic.

Phytotoxic effects on chloroplast and UHPLC-HRMS based untargeted metabolomic responses in Allium tuberosum Rottler ex Sprengel (Chinese leek) exposed to antibiotics.

Introduction of antibiotics into agricultural fields poses serious health risks to humans. This study investigated the uptake of antibiotics, their effects on metabolic pathways, and chloroplast structure changes of Allium tuberosum exposed to norfloxacin (NFL), oxytetracycline (OTC), and tetracycline (TC). Among all the antibiotic treatments, the highest accumulation of antibiotics in roots (4.15 mg/kg) and leaves (0.29 mg/kg) was TC, while in bulbs it was NFL (5.94 mg/kg). OTC was with the lowest accumulation in roots: 0.19 mg/kg, bulbs: 0.18 mg/kg, and leaves: 0.11 mg/kg. The number of mitochondira and the number of plastoglobulli increased. The chloroplast structure was disturbed under the stress of NFL, OTC, and TC. Disturbance in the chloroplast ultrastructure leads to altered chlorophyll fluorescence variables. Simultaneously, metabolomic profiling of leaves demonstrated that NFL stress regulated more of metabolic pathways than OTC and TC. Differences in metabolic pathways among the antibiotic treatments showed that each antibiotic has different impact even under the same experimental conditions. TC and NFL have more toxic effects than OTC antibiotic. Metabolic variations induced by antibiotics stress highlighted pools of metabolites that affect the metabolic activities, chlorophyll fluorescence, ultrastructural adjustments, and stimulate defensive impact in A. tubersoum. These findings provide an insight of metabolic destabilization as well as metabolic changes in defensive mechanism and stress response of A. tuberosum to different antibiotics.

Effects of antibiotics stress on growth variables, ultrastructure, and metabolite pattern of Brassica rapa ssp. chinensis.

Antibiotics frequently contaminate agricultural fields and through plant uptake enter into the food chain. This study aimed to explore the effects of antibiotics; tetracycline (TC), oxytetracycline (OTC) and norfloxacin (NF) on the growth, cell ultrastructure, and metabolite pattern of Brassica rapa ssp. chinensis. Oxytetracycline accumulated more than other antibiotics followed by TC and NF. Plant growth, chlorophyll fluorescence, and antioxidant activities were negatively affected under all antibiotic treatments. Ultrastructural investigation of mesophyll of leaves performed by transmission electron microscopy indicated that antibiotic stress caused the changes in thylakoid orientation, number of plastoglobuli, and starch grains. Identification of functional groups through Fourier transform infrared analysis indicated that carboxyl group, carbonate and ammonium ions are involved in the adsorption of antibiotics. The metabolic profiling of B. rapa leaves demonstrated that all of the antibiotics treatments distorted phenylalanine, tyrosine and tryptophan biosynthesis, d-glutamine and d-glutamate metabolism, alanine, aspartate and glutamate metabolism, phenylalanine metabolism and TCA cycle. Metabolic alterations as a result of antibiotics stress provide insights of metabolites that affect the physiological changes attributed to antibiotic stress. These results will improve the understanding of antibiotic contamination effects on plants.

Study amino acid contents, plant growth variables and cell ultrastructural changes induced by cadmium stress between two contrasting cadmium accumulating cultivars of Brassica rapa ssp. chinensis L. (pak choi).

Cadmium (Cd) is an inauspicious abiotic traction that not only influences crop productivity and its growth parameters, but also has adverse effects on human health if these crops are consumed. Among crops, leafy vegetables which are the good source of mineral and vitamins accumulate more Cd than other vegetables. It is thus important to study photosynthetic variables, amino acid composition, and ultrastructural localization of Cd differences in response to Cd accumulation between two low and high Cd accumulating Brassica rapa ssp. chinensis L. (pak choi) cultivars, differing in Cd accumulation ability. Elevated Cd concentrations significantly lowered plant growth rate, biomass, leaf gas exchange and concentrations of amino acids collated to respective controls of both cultivars. Electron microscopy indicated that the impact of high Cd level on ultrastructure of leaf cells was associated to affecting cell functionalities, i.e. irregular cell wall, withdrawal of cell membrane, and chloroplast structure which has negative impact on photosynthetic activities, thus causing considerable plant growth suppression. Damage in root cells were observed in the form of enlargement of vacuole. The energy dispersive micro X-ray spectroscopy of both cultivars leaves indicated that cellular structure exhibited exudates of Cd-dense material. Ultrastructural damages and phytotoxicity were more pronounced in high accumulator cultivar as compared to the low accumulator cultivar. These findings are useful in determining the mechanisms of differential Cd-tolerance among cultivars with different Cd tolerance abilities at cellular level.