Predicting the translocation of organic contaminants to plants is crucial to ensure the quality of agricultural goods and assess the risk of human exposure through the food web. In this study, the performance of a modified plant uptake model was evaluated considering a number of chemicals, such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs), with a range of physicochemical properties; different plant species (Ipomoea aquatica Forsk (swamp morning glory), Chrysanthemum coronarium L. (crown daisy), Zea mays L. (corn), Brassica rapa pekinensis (Chinese cabbage), Cucurbita moschata (pumpkin), Raphanus sativus L. (radish), Spinacia oleracea L. (spinach) and Capsicum annuum L. (pepper)); and different types of soil (paddy soil, laterite soil and black soil). The biases of predictions from a previously used partition-limited model were −76.4% to −99.9% relative to the measured concentrations. An overall transmission factor (αtf=0.39), calculated from a linear regression of the measured bioavailable fraction (Cbᵢₒ) and the total concentration in plants, was considered a crucial modification and was included in the modified model. Cbᵢₒ was found to better represent the chemical content available in soil for root uptake. The results from this study improve the accuracy of predictions for vegetation-uptake assessments by modifying the partition-limited model and then validating the modified model using comparisons between predicted data and measured values. The accuracy of the concentrations of organic contaminants in plants improved: when using the modified model, 89.5% of the predictions were within 40% of the actual value. The average bias was limited to 1.5%–30.5%. The model showed great potential to predict plant uptake using the bioavailable fraction concentration in soil.

Metabolic profiling in plants can be used to differentiate between treatments and to search for biomarkers for exposure. A methodology for processing Ultra-High-Performance Liquid Chromatography–Diode-Array-Detection data is devised. This methodology includes a scheme for selecting informative wavelengths, baseline removal, retention time alignment, selection of relevant retention times, and principal component analysis (PCA). Plant crude extracts from rapeseed seedling exposed to sublethal concentrations of glyphosate are used as a study case. Through this approach, plants exposed to concentrations down to 5 μM could be distinguished from the controls. The compounds responsible for this differentiation were partially identified and were different from those specific for high exposure samples, which suggests that two different responses to glyphosate are elicited in rapeseed depending on the level of exposure. The PCA loadings indicate that a combination of other metabolites could be more sensitive than the response of shikimate to detect glyphosate exposure.

To improve risk estimates at the screening stage of Ecological Risk Assessment (ERA), short duration bioassays tailored to undisturbed soil cores from the contaminated site could be useful. However, existing standardized bioassays use disturbed soil samples and often pH sensitive organisms. This is a problem as naturally acidic soils are widespread. Changing soil properties to suit the test organism may change metal bioavailability, leading to erroneous risk estimates. For bioassays in undisturbed soil cores to be effective, species able to withstand natural soil properties must be identified. This review presents a critical examination of bioassay species' tolerance of acidic soils and sensitivity to metal contaminants such as Pb and Zn. Promising organisms include; Dendrobaena octaedra, Folsomia candida, Caenorhabditis elegans, Oppia nitens, Brassica rapa, Trifolium pratense, Allium cepa, Quercus rubra and Acer rubrum. The MetSTICK test and the Bait lamina test were also identified as suitable microorganism tests.

Studying tolerance limits in organisms exposed to climatic variations is key to understanding effects on behaviour and physiology. The presence of pollutants may influence these tolerance limits, by altering the toxicity or bioavailability of the chemical. In this work, the plant species Brassica rapa and Triticum aestivum and the earthworm Eisenia andrei were exposed to different levels of soil moisture and carbaryl, as natural and chemical stressors, respectively. Both stress factors were tested individually, as well as in combination. Acute and chronic tests were performed and results were discussed in order to evaluate the responses of organisms to the combination of stressors. When possible, data was fitted to widely employed models for describing chemical mixture responses. Synergistic interactions were observed in earthworms exposed to carbaryl and drought conditions, while antagonistic interactions were more representative for plants, especially in relation to biomass loss under flood-simulation conditions.

Plants need to be included to develop a comprehensive toxicity profile for nanoparticles. Effects of five types of nanoparticles (multi-walled carbon nanotube, aluminum, alumina, zinc, and zinc oxide) on seed germination and root growth of six higher plant species (radish, rape, ryegrass, lettuce, corn, and cucumber) were investigated. Seed germination was not affected except for the inhibition of nanoscale zinc (nano-Zn) on ryegrass and zinc oxide (nano-ZnO) on corn at 2000 mg/L. Inhibition on root growth varied greatly among nanoparticles and plants. Suspensions of 2000 mg/L nano-Zn or nano-ZnO practically terminated root elongation of the tested plant species. Fifty percent inhibitory concentrations (IC50) of nano-Zn and nano-ZnO were estimated to be near 50 mg/L for radish, and about 20 mg/L for rape and ryegrass. The inhibition occurred during the seed incubation process rather than seed soaking stage. These results are significant in terms of use and disposal of engineered nanoparticles. Engineered nanoparticles can inhibit the seed germination and root growth.

Biological tests with plant seeds have been adopted in many studies to investigate the phytotoxicity of pollutants to facilitate the control of risks and remain to be optimized. In this work, the experiment with a small sample size (Experiment 1) and the experiment with a large one (Experiment 2) were designed to study the effect of tetracycline (TC) on Chinese cabbage (Brassica rapa L.) at seed germination and radicle elongation stages. At the former stage, germination number data were obtained to analyze the germination energy (GE) and to judge the probability of the number of germinated seeds (Pₙ) by the binomial distribution model in Experiment 1. While germination time-to-number data were obtained to analyze the mean time to germination (MGT), the estimate of mean time to germination (EMGT) by survival analysis method, the time to germination for 50% of total seeds (T₅₀) and the germination rate (GR) besides GE in Experiment 2. At the latter stage, the data of radicle length (RL) were obtained in all the experiments and the influence from the former stage on this stage was excluded in Experiment 2 but not in Experiment 1. Results showed that TC had universal adverse effects on the latter stage but not on the former stage in the experiments. Considering the availability of germination data for statistical analysis and the robustness of RL data, the methods adopted in Experiment 2 were more feasible than those in Experiment 1. In addition, Chinese cabbage seeds with medium size have the character of rapid germination compared with the commonly used crop species and can be used to shorten the experimental cycle to study the responses of seeds to pollutants to evaluate the phytotoxicity.We introduced survival analysis method to analyze the germination time-to-number data obtained in seed germination test to evaluate the phytotoxicity of tetracycline.

To better determine phytotoxicity thresholds for metals in the soil, studies should use actual field-contaminated soil samples rather than metal-spiked soil preparations. However, there are surprisingly few such data available for Cu phytotoxicity in field-contaminated soils. Moreover, these studies differ from each other with regards to soil characteristics and experimental setups. This study aimed at more accurately estimating Cu phytotoxicity thresholds using field-collected agricultural soils (Entisols) from areas exposed to contamination from Cu mining. For this purpose, the exposure to Cu was assessed by measuring total soil Cu, soluble Cu, free Cu2+ activity, and Cu in the plant aerial tissues. On the other hand, two bioassay durations (short-term and long-term), three plant species (Avena sativa L., Brassica rapa CrGC syn. Rbr, and Lolium perenne L.), and five biometric endpoints (shoot length and weight, root length and weight, and number of seed pods) were considered. Overall plant growth was best predicted by total Cu content of the soil. Despite some confounding factors, it was possible to determine EC10, EC25 and EC50 of total Cu in the soil. Brassica rapa was more sensitive than Avena sativa for all endpoints, while Lolium perenne was of intermediate sensitivity. For the short-term bioassay (21 days for all three species), the averaged EC10, EC25 and EC50 values of total soil Cu (in mg kg−1) were 356, 621, and 904, respectively. For the long-term bioassay (62 days for oat and 42 days for turnip), the averaged EC10, EC25 and EC50 values of total soil Cu (in mg kg−1) were 355, 513, and 688, respectively. The obtained results indicate that chronic test is a suitable method for assessing Cu phytotoxicity in field-contaminated soils.

Exogenous regulation of plant physiology is a kind of effective approach to help plant grow under Cd (cadmium)-contaminated environment. CA (cinnamaldehyde) is an environmental friendly natural compound with medicinal properties and antimicrobial activities. In this work, we found that CA was able to confer plant Cd tolerance by priming defense in the root of B. rapa. Pretreatment with CA attenuated the phytotoxicity induced by subsequent Cd stress, such as root growth inhibition, ROS accumulation, oxidative injury, and cell death in root tip. Cd stress decreased the intracellular Ca²⁺ level in roots, which could be enhanced by pretreatment with CA. Pretreatment with a Ca²⁺ chelator or a Ca²⁺ channel blocker blocked all the beneficial effects of CA on the increase in the intracellular Ca²⁺ level and the amelioration of physiological injury in roots under Cd stress. Correlation analysis combined with cluster analysis suggested that CA was able to prime plant defense by regulating endogenous Ca²⁺ in order to facilitate Cd tolerance. These results shed a new light on the novel role of CA in modulating plant resistant physiology against metal stress, which may extend our knowledge on both CA and plant Cd tolerance.

Soil washing is an effective technology for the remediation of soils contaminated with various metals. However, the bioavailability of residual metals in soils and soil properties can be changed during the washing processes. In this study, we used four amendments to revitalize mixed chelator (MC)–washed soils (WS). These amendments included zeolite, CaCO₃, biochar, and chicken manure. Results showed that inorganic amendments reduced the available Cd and Zn concentrations, while organic amendments, particularly chicken manure, reduced the Pb bioavailability in WS. The combination of 0.2% CaCO₃ and 2% chicken manure amendments reduced the Cd, Pb, and Zn bioavailability by 45.8%, 77.8%, and 15.0% compared with the control treatment, respectively. The inorganic amendments should increase the seed germination rate of Chinese cabbage (Brassica rapa L.). However, the shoot growth decreased significantly. The combination of amendments cannot increase the seed germination but can significantly increase the shoot growth of Chinese cabbage compared with the control. The combination of amendments enhanced the fertility of WS, particularly available P and exchangeable K, which may improve plant growth. These results suggested that the combination of amendments, especially CaCO₃ (0.2%) and chicken manure (2%), can be used to revitalize MC-WS.

Histochemical and biochemical approaches were used to investigate the phytotoxicity induced by microcystin-LR (MC-LR) in the shoots of Brassica rapa seedlings. MC-LR exposure was able to induce oxidative stress by triggering the over-generation of reactive oxygen species (ROS) including superoxide anion radical (O₂ [Sʸᵐᵇᵒˡ: ˢᵉᵉ ᵗᵉˣᵗ] ⁻ ) and hydrogen peroxide (H₂O₂) in the shoots of B. rapa. MC-LR exposure led to the significant increase in the concentration of endogenous nitric oxide (NO) in B. rapa. However, such increase was completely suppressed by the treatment with nitrate reductase (NR) inhibitor NaN₃, while L-NMMA, a NO synthase (NOS) inhibitor, had only slight effect on the content of endogenous NO in MC-LR-treated plant. These data suggested that NR-dependent pathway was the main source for endogenous NO generation under MC-LR stress. Afterwards, treatment with NaN₃ reduced the ROS generation, lipid peroxidation, and loss of membrane integrity in MC-LR-treated plant. MC-LR stress induced the increase in the expression of superoxide dismutase, ascorbate peroxidase, and catalase. However, such an effect could be reversed by the treatment with NaN₃. These results indicate that NR-dependent NO production mediates MC-LR-induced oxidative stress by triggering the over-generation of ROS in B. rapa.