Investigation of chlorophyll degradation by tetracycline

Changes in Metabolism and Content of Chlorophyll in Common Duckweed (Lemna minor L.) Caused by Environmental Contamination with Fluorides

The impact of fluorine on plants remains poorly understood. We examined duckweed growth in extracts of soil contaminated with fluorine leached from chicken manure. Additionally, fluorine levels were analyzed in fresh manure, outdoor-stored manure, and soil samples at varying distances from the manure pile. Fresh manure contained 37-48 mg F- × kg-1, while soil extracts contained 2.1 to 4.9 mg F- × kg-1. We evaluated the physiological effects of fluorine on duckweed cultured on soil extracts or in 50% Murashige-Skoog (MS) medium supplemented with fluorine concentrations matching those in soil samples (2.1 to 4.9 mg F- × L-1), as well as at 0, 4, and 210 mg × L-1. Duckweed exposed to fluorine displayed similar toxicity symptoms whether in soil extracts or supplemented medium. Fluoride at concentrations of 2.1 to 4.9 mg F- × L-1 reduced the intact chlorophyll content, binding the porphyrin ring at position 32 without affecting Mg2+. This reaction resulted in chlorophyll a absorption peak shifted towards shorter wavelengths and formation of a new band of the F--chlorophyll a complex at λ = 421 nm. Moreover, plants exposed to low concentrations of fluorine exhibited increased activities of aminolevulinic acid dehydratase and chlorophyllase, whereas the activities of both enzymes sharply declined when the fluoride concentration exceeded 4.9 mg × L-1. Consequently, fluorine damages chlorophyll a, disrupts the activity of chlorophyll-metabolizing enzymes, and diminishes the plant growth rate, even when the effects of these disruptions are too subtle to be discerned by the naked human eye.

Studies on the Efficiency of Iron Release from Fe(III)-EDTA and Fe(III)-Cit and the Suitability of These Compounds for Tetracycline Degradation

Iron ions can be used to degrade tetracycline dispersed in nature. Studies of absorption and fluorescence spectra and quantum chemistry calculations showed that iron is more readily released from Fe(III)-citrate than from Fe(III)-EDTA, so Fe(III)-citrate (Fe(III)-Cit) is more suitable for tetracycline (TC) degradation. At 30 °C, a severe degradation of TC by Fe(III)-Cit occurred as early as after 3 days of incubation in the light, and after 5 days in the dark. In contrast, the degradation of TC by Fe(III)-EDTA proceeded very slowly in the dark. By the fifth day of incubation of TC with Fe(III)-Cit in darkness, the concentrations of the former compound dropped by 55% and 75%, at 20 °C and 30 °C, respectively. The decrease in tetracycline concentrations caused by Fe(III)-EDTA in darkness at the same temperatures was only 2% and 6%, respectively. Light increased the degradation rates of TC by Fe(III)-EDTA to 20% and 56% at 20 °C and 30 °C, respectively. The key role of the light in the degradation of tetracycline by Fe(III)-EDTA was thus demonstrated. The TC degradation reaction showed a second-order kinetics. The rate constants of Fe(III)-Cit-induced TC degradation at 20 °C and 30 °C in darkness were k = 4238 M^-1day^-1 and k = 11,330 M^-1day^-1, respectively, while for Fe(III)-EDTA were 55 M^-1day^-1 and 226 M^-1day^-1. In light, these constants were k = 15,440 M^-1day^-1 and k = 40,270 M^-1day^-1 for Fe(III)-Cit and k = 1012 M^-1day^-1 and 2050 M^-1day^-1 at 20 °C and 30 °C; respectively. A possible reason for the higher TC degradation rate caused by Fe(III)-Cit can be the result of its lower thermodynamical stability compared with Fe(III)-EDTA, which we confirmed with our quantum chemistry calculations. Two quantum chemistry calculations showed that the iron complex with EDTA is more stable (the free energy of the ensemble is 15.8 kcal/mol lower) than the iron complex with Cit; hence, Fe release from Fe(III)-EDTA is less effective.

Inactivation Mechanism of Algal Chlorophyll by Allelochemical Quercetin

Cyanobacteria harmful algal blooms (CyanoHABs) are a global concern. Application of allelochemicals is a promising solution for cyanobacteria control, due to its high efficiency, low cost and ecological safety. Flavonoids (natural polyphenols produced by aquatic plants) are reported capable of effectively inhibiting the growth of algae; however, the molecular mechanism of algae chlorophyll inactivation is still unclear. In this study, quercetin was used as a typical flavonoid, to investigate the inactivation effect of allelochemical on Microcystis aeruginosa chlorophyll a. The absorption and fluorescence spectra showed that chlorophyll reacted with quercetin to form pheophytin, and the formation rate of pheophytin increased with increasing quercetin concentration (1 × 10^-5-1 × 10^-2 M). FTIR spectra and DFT calculation showed that Mg²⁺ complexed with the 3-OH and 4-C = O groups in the quercetin ring C so that chlorophyll was inactivated due to the loss of Mg²⁺ ions. Overall, this study revealed that quercetin inactivated chlorophyll a of cyanobacteria by capturing Mg²⁺ ions, providing insights into the molecular mechanisms of algal bloom control by allelochemicals.

Physiological and Biochemical Parameters of Common Duckweed Lemna minor after the Exposure to Tetracycline and the Recovery from This Stress

In this study, the ability of Lemna minor L. to recover to normal growth, after being degraded in a tetracycline-containing medium, was extensively investigated. The plants were exposed to tetracycline (TC) at concentrations of 1, 2.5, and 10 mM. Subsequently, their physiological status was analysed against the following criteria: rate of plant growth; free radical accumulation; antioxidant enzyme activity; chlorophyll content; HSP70 protein content; cell membrane permeability, and mitochondrial activity. The study showed that duckweed can considerably recover from the damage caused by antibiotics, within a week of cessation of stress. Of the plant properties analysed, mitochondrial activity was the most sensitive to antibiotic-induced disturbances. After transferring the plants to a tetracycline-free medium, all plant parameters improved significantly, except for the mitochondrial activity in the plants grown on the medium containing the highest dose of tetracycline. In the plants treated with this antibiotic at the concentration of 10 mM, the proportion of dead mitochondria increased and was as high as 93% after one week from the beginning of the recovery phase, even after the transfer to the tetracycline-free medium.

Toxicity of chlortetracycline and oxytetracycline on Vallisneria natans (Lour.) Hare

Tetracyclines are frequently detected in water bodies due to their widespread use in aquaculture and animal husbandry. A hydroponic experiment was conducted to explore the phytotoxic effects of Vallisneria natans (Lour.) Hare exposed to various concentrations of chlortetracycline (CTC) and oxytetracycline (OTC) (0, 0.1, 1, 10, 30, 50, and 100 mg/L) for 7 days (7 D) and 14 days (14 D), respectively. The results showed that similar to OTC treatment for 7 D, the relative growth rates (RGR) and catalase (CAT) activity of V. natans, after 7 D of CTC exposure, decreased significantly at 10 mg/L and 30 mg/L, respectively. The content of soluble protein notably decreased when CTC ≥ 10 mg/L and OTC ≥ 30 mg/L. The hydrogen peroxide (H₂O₂) content was significantly stimulated when OTC ≥ 10 mg/L, while it hardly changed when exposed to CTC. After 14 D, the malondialdehyde (MDA) and H₂O₂ contents of V. natans were significantly higher than those of the control group under a high concentration of OTC (≥ 30 mg/L), but they did not change significantly under a high concentration of CTC. The activity of polyphenol oxidase (PPO), under CTC treatment after 14 D, showed first a significant increase then decreases; the maximum value (125% of the control) was noticed at 10 mg/L CTC, while it remained unchanged when exposed to OTC. The soluble protein content significantly decreased at 10 mg/L CTC and 0.1 mg/L OTC, respectively. The RGR, CAT, and peroxidase (POD) activities, similar to OTC treatment after 14 D, decreased evidently when CTC was 10 mg/L, 30 mg/L, and 0.1 mg/L, respectively. CTC and OTC harm the chlorophyll content of V. natans after 14 D, and the reductions of chlorophyll a and carotenoid were more pronounced than chlorophyll b. The results suggest that CTC and OTC both have a negative effect on the growth of V. natans, and OTC can cause oxidative damage in V. natans but CTC harms the metabolism process without inducing oxidative damage. Overall, the toxicity of OTC to V. natans is stronger than that of CTC.

Different Inhibitory Effects of Erythromycin and Chlortetracycline on Early Growth of Brassica campestris Seedlings

Veterinary antibiotics, including erythromycin (Ery) and chlortetracycline (CTC), are often detected in agricultural land. Although these contaminants affect plant growth and development, their effects on crops remain elusive. In this study, the effects of Ery and CTC on plant growth were investigated and compared by analyzing transcript abundance in Brassica campestris seedlings. Treatment with Ery and/or CTC reduced chlorophyll content in leaves and photosynthetic efficiency. Examination of the chloroplast ultrastructure revealed the presence of abnormally shaped plastids in response to Ery and CTC treatments. The antibiotics produced similar phenotypes of lower accumulation of photosynthetic genes, including RBCL and LHCB1.1. Analysis of the transcript levels revealed that Ery and CTC differentially down-regulated genes involved in the tetrapyrrole biosynthetic pathway and primary root growth. In the presence of Ery and CTC, chloroplasts were undeveloped and photosynthesis efficiency was reduced. These results suggest that both Ery and CTC individually affect gene expression and influence plant physiological activity, independently of one another.

Selenium biofortification enhances ROS scavenge system increasing yield of coffee plants

There are conclusive evidences of selenium (Se) deficiency in Brazilian soils and foods. Brazil is the largest producer and consumer of coffee worldwide, which favors agronomic biofortification of its coffee. This study aimed to evaluate effects of foliar application of three formulations and six rates of Se on antioxidant metabolism, agronomic biofortification and yield of coffee beans. Seven Se concentrations (0, 10, 20, 40, 80, 100 and 160 mg L^-1) were applied from three formulations of Se (sodium selenate, nano-Se 1500, and nano-Se 5000). Selenium application up to 40 mg L^-1 increased the concentration of photosynthetic pigments such as chlorophylls, pheophytins and carotenoids in coffee leaves. Foliar application of Se ranging from 20 to 80 mg L^-1 decreased lipid peroxidation and concentration of hydrogen peroxide, but increased superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase activities in coffee leaves. These results indicated that foliar Se application stimulates antioxidative metabolism to mitigate reactive oxygen species. Foliar application of 20 mg Se L^-1 of sodium selenate increased coffee yield by 38%, and 160 mg Se L^-1 of nano-Se 5000 increased dramatically coffee yield by 42%. Selenium concentration in grains ranged from 0.116 to 4.47 mg kg^-1 (sodium selenate), 4.84 mg kg^-1 (nano-Se 1500) and 5.82 mg kg^-1 (nano-Se 5000). The results suggest the beneficial effect of Se on the increment of photosynthetic pigments, antioxidative metabolism, increased coffee yield and nutritional quality of grains. The recommended foliar Se application in this study can mitigate abiotic stressors such as high temperatures resulting in higher yield of coffee plants.

Coffea arabica seedlings genotypes are tolerant to high induced selenium stress: Evidence from physiological plant responses and antioxidative performance

Selenium (Se) is considered a beneficial element to higher plants based on its regulation of antioxidative system under abiotic or biotic stresses. However, the limit of beneficial and toxic physiological effects of Se is very narrow. In the present study, the antioxidant performance, nutritional composition, long-distance transport of Se, photosynthetic pigments, and growth of Coffea arabica genotypes in response to Se concentration in solution were evaluated. Five Coffea arabica genotypes (Obatã, IPR99, IAC125, IPR100 and Catucaí) were used, which were grown in the absence and presence of Se (0 and 1.0 mmol L^-1) in nutrient solution. The application of 1 mmol L^-1 Se promoted root browning in all genotypes. There were no visual symptoms of leaf toxicity, but there was a reduction in the concentration of phosphorus and sulfur in the shoots of plants exposed to high Se concentration. Except for genotype Obatã, the coffee seedlings presented strategies for regulating Se uptake by reducing long-distance transport of Se from roots to shoots. The concentrations of total chlorophyll, total pheophytin, and carotenoids were negatively affected in genotypes Obatã, IPR99, and IAC125 upon exposure to Se at 1 mmol L^-1. H₂O₂ production was reduced in genotypes IPR99, IPR100, and IAC125 upon exposure to Se, resulting in lower activity of superoxide dismutase (SOD), and catalase (CAT). These results suggest that antioxidant metabolism was effective in regulating oxidative stress in plants treated with Se. The increase in sucrose, and decrease in SOD, CAT and ascorbate peroxidase (APX) activities, as well as Se compartmentalization in the roots, were the main biochemical and physiological modulatory effects of coffee seedlings under stress conditions due to excess of Se.