Background: Nanoparticles (NPs) serve various industrial and household purposes, and their increasing use creates an environmental hazard because of their uncontrolled release into ecosystems. An important aspect of the risk assessment of NPs is to understand their interactions with plants. The aim of this study was to examine the effect of Au (10 and 20 ppm), Ag, and Pt (20 and 40 ppm) NPs on oakleaf lettuce, with particular emphasis on plant antioxidative mechanisms. Nanoparticles were applied once on the leaves of 2-week-old lettuce seedlings, after next week laboratory analyses were performed. Results: The antioxidant potential of oakleaf lettuce seedlings sprayed with metal NPs at different concentrations was investigated. Chlorophylls, fresh and dry weight were also determined. Foliar exposure of the seedlings to metal NPs did not affect ascorbate peroxidase activity, total peroxidase activity increased after Au-NPs treatment, but decreased after applying Ag-NPs and Pt-NPs. Both concentrations of Au-NPs and Pt-NPs tested caused an increase in glutathione (GSH) content, while no NPs affected L-ascorbic acid content in the plants. Ag-NPs and Pt-NPs applied as 40 ppm solution increased total phenolics content by 17 and 15%, respectively, compared to the control. Carotenoids content increased when Ag-NPs and Au-NPs (20 and 40 ppm) and Pt-NPs (20 ppm) were applied. Plants treated with 40 ppm of Ag-NPs and Pt-NPs showed significantly higher total antioxidant capacity and higher concentration of chlorophyll a (only for Ag-NPs) than control. Pt-NPs applied as 40 ppm increased fresh weight and total dry weight of lettuce shoot. Conclusions: Results showed that the concentrations of NPs applied and various types of metal NPs had varying impact on the antioxidant status of oakleaf lettuce. Alteration of POX activity and in biosynthesis of glutathione, total phenolics, and carotenoids due to metal NPs showed that tested nanoparticles can act as stress stimuli. However, judging by the slight changes in chlorophyll concentrations and in the fresh and dry weight of the plants, and even based on the some increases in these traits after M-NPs treatment, the stress intensity was relatively low, and the plants were able to cope with its negative effects.

Nanoparticles (NPs) significantly modify the physiological functions and metabolome of plants. The purpose of the study was to investigate the effect of CeO2, Fe2O3, SnO2, TiO2, and SiO2 nanoparticles, applied in foliar spraying of oakleaf lettuce at concentrations 0.75% to 6%, on the antioxidant enzyme activity and content of non-enzymatic antioxidants, chlorophyll pigments, fresh weight (FW) and dry weight (DW). It was found that 3% Fe2O3-NPs caused a 27% decrease in fresh weight compared to control plants. Fe2O3-NPs caused an increase in dry weight (g 100 g−1 FW) when compared to the control for all concentrations, but total DW (g per plant) was similar for all NPs treatments. Significant increases in chlorophyll a + b content after treatment with 1.5% and 6% SiO2-NPs, 3% Fe2O3-NPs, and 3% TiO2-NPs were noted. Fe2O3-NPs caused a significant increase in the activity of ascorbate peroxidase, guaiacol peroxidase, and catalase (only for 3% Fe2O3-NPs). SnO2-NPs decreased ascorbate peroxidase (APX) and guaiacol peroxidase (GPOX) activity (for all tested concentrations) but increased catalase (CAT) activity when a 3% suspension of these NPs was applied. The level of glutathione (GSH) increased due to application of all metal/metalloid oxides, with the exception of SnO2-NPs. When all concentrations of TiO2-NPs were applied, L-ascorbic acid increased significantly, as well as increasing at higher concentrations of SiO2-NPs (3% and 6%) and at 0.75% and 3% Fe2O3-NPs. SiO2-NPs and TiO2-NPs significantly elevated the carotenoid and total phenolic content in treated plants compared to the control. The total antioxidant capacity of plants treated with 3% CeO2-NPs was almost twice as high as that of the control.

Kale is a plant known and valued since antiquity as a healthy vegetable crop, used for culinary, decorative, but also healing purposes. The aim of the study was to examine the effect of harvest date on physiological status and nutritional composition of two kale cultivars: 'Winterbor' F 1 (blue-green leaves) and 'Redbor' F 1 (red-purple leaves). The leaves were harvested in three periods: before frost (>0°C), after medium (−5.0°C) and heavy frost (−15.0°C). Content of dry weight, soluble sugars, l-ascorbic acid, carotenoids, chlorophylls, polyphenols, anthocyanins, as well as antioxidant activity and peroxidase activity were determined. Cold temperature significantly affected bioactive compounds of kale. The content of dry weight, soluble sugars, l-ascorbic acid, phenolics, and antioxidant activity increased after medium frosts for both cultivars. The level of anthocyanins also increased significantly for the 'Redbor' F 1 cultivar. After strong frost, most of the tested parameters (content of dry weight, soluble sugars, phenolics, anthocyanins, and total antioxidant and peroxidase activity) significantly increased. The chlorophyll a content was reduced by heavy frost in both seasons. Harvesting kale before and after frost may allow the level of biologically active ingredients to be regulated as cold also significantly affects the physiological status of the plants.

The aim of the study was to determine the effects of CeO2, Fe2O3, and SiO2 nanoparticles on the metabolism of phenols and flavonoids and the antioxidant status of butterhead lettuce...

Nowadays, there is an increasing interest in nanoparticle (NP) technology used in household and industrial products. It could cause an accumulation and dispersion of NPs in the environment, with possible harmful effects on living organisms. Nanoparticles significantly affect plants and alter their physiology and biochemical pathways, and nanotechnology can be used to improve plant characteristics that are desirable by humans. Therefore, more extensive studies of NP interactions with plants are still needed. The aim of this report is to investigate the effect of TiO2 nanoparticles (TiO2-NPs) on the enzymatic and non-enzymatic antioxidants, fresh and dry weights, and malondialdehyde contents in oakleaf lettuce seedlings. Plants were foliar treated with a 0.75% suspension of TiO2-NPs, while control plants were sprayed with deionized water. Leaves were sampled 4, 7, 9, 11, and 13 days after the treatment. The effects of TiO2-NPs were time-dependent, but the most spectacular changes were observed 4 days after the treatment. Exposure of the plants to TiO2-NPs significantly increased the contents of glutathione at all sampling points, total phenolics at days 4 and 13, and L-ascorbic acid at 4, 7, and 11 days after the treatment. Elevated levels of ascorbate peroxidase and guaiacol peroxidase activities were recorded at days 4 and 13, respectively. Total antioxidant capacity increased initially in treated seedlings, when compared with the control, and then decreased. On day 7, higher fresh and dry weights, as well as malondialdehyde contents in TiO2-NPs treated plants were observed, compared with the control. The study demonstrated that the activation of some antioxidant system components due to TiO2-NPs treatment was connected with the induction of mild oxidative stress, with no external symptoms of NP toxicity in oakleaf lettuce.

Background Most nanoparticles (NPs) have a significant impact on the structure and function of the plant photosynthetic apparatus. However, their spectrum of action varies significantly, from beneficial stimulation to toxicity, depending on the type of NPs, the concentration used and plant genotypic diversity. Photosynthetic performance can be assessed through chlorophyll a fluorescence (ChlF) measurements. These data allow to indirectly obtain detailed information about primary light reactions, thylakoid electron transport reactions, dark enzymatic stroma reactions, slow regulatory processes, processes at the pigment level. It makes possible, together with leaf reflectance performance, to evaluate photosynthesis sensitivity to stress stimuli. Results We investigated effects of different metal and metal(oid) oxide nanoparticles on photosynthesis of oakleaf lettuce seedlings by monitoring the chlorophyll a fluorescence light radiation and reflectance from the leaves. Observations of ChlF parameters and changes in leaf morphology were carried out for 9 days in two-day intervals. Spectrophotometric studies were performed at 9th day. Suspensions of NPs with the following concentrations were used: 6% TiO2, SiO2; 3% CeO2, SnO2, Fe2O3; 0.004% (40 ppm) Ag; 0.002% (20 ppm) Au. Nanoparticles were applied directly on the leaves which caused small symptoms of chlorosis, necrosis and leaf veins deformation, but the plants fully recovered to the initial morphological state at 9th day. Leaf reflectance analysis showed an increase in FRI for SiO2-NPs and CeO2-NPs treatments and ARI2 for Fe2O3, however, WBI and PRI coefficients for the latter nanoparticle were lower than in control. Chlorophyll a fluorescence parameters have changed due to NPs treatment. Fe2O3-NPs caused an increase in Fv/F0, PIABS, ET0/RC, DI0/RC, ABS/RC in different time points in comparison to control, also Ag, Au and SnO2 treatment caused an increase in Fv/F0, PIABS or ET0/RC, respectively. On the other hand, TiO2-NPs caused a decrease in Fv/Fm and Fv/F0 parameters, but an increase in DI0/RC value was observed. SnO2-NPs decreased PIABS, but increased ET0/RC than compared to control. Nanoparticles affected the shape of the O-J-I-P curve in slight manner, however, further analyses showed unfavourable changes within the PSII antenna, manifested by a slowdown in the transport of electrons between the Chl molecules of the light-harvesting complex II and the active center of PSII due to NPs application. Conclusion Changes in ChlF parameters and leaf reflectance values clearly proved the significant influence of NPs on the functioning of the photosynthetic apparatus, especially right after NPs application. The nature of these changes was strictly depended on the type of nanoparticles and sometimes underwent very significant changes over time. The greatest changes in ChlF parameters were caused by Fe2O3 nanoparticles, followed by TiO2-NPs. After slight response of O-J-I-P curves to treatment of the plants with NPs the course of the light phase of photosynthesis stabilized and at 9th day were comparable to the control curve.

Polypropylene (PP) covers are used in radish (Raphanus sativus L. var. sativus) production to provide better microclimate for improving yield and quality, but disposing of non-degradable covers is difficult and expensive. In this work, nonwovens prepared from biodegradable polymers (aliphatic-aromatic copolyesters with and without fatty acid dimers: SB48/11, SB20/13, SB21/13, SB28/13) were tested in the field as substitutes for nonwoven PP. Minimum air temperature under biodegradable covers was higher by 0.6-0.8 °C than under nonwoven PP, but photosynthetically active radiation (PAR) transmission was lower by 4.1% (SB20/13) and 7.1% (SB21/13). We observed a decrease in marketable yield of plants covered with biodegradable fleeces by 1.01 to 2.90 kg m-2 (SB48/11 and SB28/13, respectively) in spring seasons, but similar yields to nonwoven PP were obtained in the autumn seasons. Dry weight, soluble sugars, L-ascorbic acid, pigments content in radish was dependent on a specific set of environmental conditions rather than on the type of cover. However, L-ascorbic acid content in the roots increased significantly by 6.4 and 2.9 mg 100 g-1 FW for SB48/11 and SB20/13 (in one trial), respectively, as compared to nonwoven PP. It is possible to use biodegradable nonwovens as floating covers for radish cultivated in seasons with temperature drops.

This study evaluated sage (Salvia officinalis L.) genotypes (cultivars: ‘Berggarten’, ‘Icterina’, ‘Purpurascens’, ‘Tricolor’, local Czech accessions from the Lednice region, South Moravia: ‘LDN-1’ and ‘LDN-2’) subjected to chilling (4 °C, 2 weeks, 18 °C ‒ control) for comparison of antioxidant defence systems. Chilling caused the most significant increase in the peroxidase activity in ‘Purpurascens’ and ‘Tricolor’, by 108.5% and 15.7%, respectively, while the catalase was unaffected by the low temperature. The phenolics increased in ‘Purpurascens’ and ‘LDN-1’ by 17.2% and 18.1%, respectively, and decreased in ‘LDN-2’ and ‘Tricolor’, by 10.6% and 11.7%, respectively, as a result of the chilling. In the sage treated with chilling, the scavenging of 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH•) was higher (by 3%, on average), especially in ‘Berggarten’, ‘Icterina’, and ‘Purpurascens’, than in the control. However, the chilled ‘LDN-2’ and ‘Tricolor’ showed lower antioxidant∙ activity in comparison to the control. The malondialdehyde remained stable or was higher in the control, with the only exception being ‘LDN-1’, where its content increased by 11.4% in the chilled sage. In most genotypes, the content of the dry weight increased in the chilled plants by 9.4% on average. The responses of ‘Icterina’ and ‘Purpurascens’ to the low temperature was the most significant, but resulted from different physiological mechanisms. ‘Purpurascens’ showed the highest increase in the peroxidase activity due to the chilling, while the highest increase in the antioxidant activity was observed for ‘Icterina’.