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The potential of Leersia hexandra grass in phytoremediation and natural attenuation of three groups of bacteria in soil contaminated with crude oil was evaluated for 180 days. The quantities of new shoots, root and aerial biomass were evaluated; changes in antioxidant concentrations in leaf and root caused by abiotic stress; population densities of Azoto-bacter, Azospirillum and Pseudomonas; and microbial respiration. The experimental data showed oil-induced increases of 315% and 196% in new shoots and root phytomass, respectively, and a 44% decrease in leaf + stem phytomass. The enzymatic defence in the grass leaf was manifested by higher concentrations of hydrogen peroxide, phenylalanine ammonium lyase and total flavonoids; the increases fluctuated from 35% to 52%. The response in the root was positive in catalase (16%), and in ammonium phenylalanine lyase, it increased 275% due to the effect of crude oil. The group of indigenous Azotobacter bacteria were tolerant to crude oil exposure, both in the phytoremediation process and in natural attenuation; the population densities varied from 212 to 438 x 10³ colony-forming units (CFUs); they are greater than 49% to 106% compared to densities in control soil. Azospirillum spp. and Pseudomonas spp. recorded population abiotic stress. The grass activates enzymatic and plant defence, complementing microbial respiration in response to adaptation to crude oil. [ABSTRACT FROM AUTHOR]

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The tomato crop is susceptible to various types of stress, both biotic and abiotic, which affect the morphology, physiology, biochemistry, and genetic regulation of plants. Among the biotic factors, is the phytopathogen Fusarium oxysporum f. sp. lycopersici (Fol), which can cause losses of up to 100%. Graphene–Cu nanocomposites have emerged as a potential alternative for pathogen control, thanks to their antimicrobial activity and their ability to induce the activation of the antioxidant defense system in plants. In the present study, the effect of the Graphene–Cu nanocomposites and the functionalization of graphene in the tomato crop inoculated with Fol was evaluated, analyzing their impacts on the antioxidant defense system, the foliar water potential (Ψh), and the efficiency of photosystem II (PSII). The results demonstrated multiple positive effects; in particular, the Graphene–Cu nanocomposite managed to delay the incidence of the "vascular wilt" disease and reduce the severity by 29.0%. This translated into an increase in the content of photosynthetic pigments and an increase in fruit production compared with Fol. In addition, the antioxidant system of the plants was improved, increasing the content of glutathione, flavonoids, and anthocyanins, and the activity of the GPX, PAL, and CAT enzymes. Regarding the impact on the water potential and the efficiency of the PSII, the plants inoculated with Fol and treated with the Graphene–Cu nanocomposite responded better to biotic stress compared with Fol, reducing water potential by up to 31.7% and Fv/Fm levels by 32.0%. [ABSTRACT FROM AUTHOR]

The metabolic activity of the fruits continues even after harvest, which results in the loss of bioactive compounds, a decrease in the quality of the fruits, softening and browning, among other negative effects. The use of certain elements such as silicon can improve postharvest quality, since it is involved in the metabolic, physiological and structural activity of plants, moreover can increase the quality of the fruits. In addition, nanotechnology has had a positive impact on crop yield, nutritional value, fruit quality and can improve antioxidant activity. For these reasons, the use of beneficial elements such as silicon in the form of nanoparticles can be a viable option to improve the characteristics of the fruits. In the present study was evaluated the application of potassium silicate (125, 250 and 500 mg L-1) and SiO2 nanoparticles (125, 250 and 500 mg L-1) during the development of the crop. The results showed that the application of silicon (potassium silicate and silicon nanoparticles) increased the content of total soluble solids (up to 15.6% higher than control), titratable acidity (up to 38.8% higher than control), vitamin C (up to 78.2% higher than control), phenols (up to 22% higher than control), flavonoids (up to 64.6% higher than control), and antioxidant activity in lipophilic compounds (up to 56.2% higher than control). This study suggests that the use of silicon can be a good option to increase the content of bioactive compounds in cucumber fruits when they are applied during the development of the crop. [ABSTRACT FROM AUTHOR]