Abstract
In an effort to identify novel biopesticides, the present study aimed to assess the effects of Philodendron meridionale (Buturi & Sakur) stem and leaf ketonic and ethanolic extracts (SKE, SEE, LKE, and LEE, respectively) on the germination, growth, root respiration, and enzymatic activities of Lactuca sativa L. seeds, and to measure the associated saponins, phenolics, and flavonoids that may possess herbicidal, pharmaceutical, or pesticidal activities. The extracts were obtained using a modified Soxhlet apparatus and methanolic extracts of 0.1, 0.25, 0.5, 0.75 and 1.0 mg.mL-1 were tested, with water and methanol as a control. The presence of saponins and the concentration of phenolic compounds were determined. Allelopathic activity was evaluated in tests of germination, growth, cellular respiration and enzymatic activity. The presence of saponins and the concentration of phenolic compounds equivalent to 225.12 for LKE, 240.45 for LEE, 193.28 for SKE, and 265.14 for SEE (mg·g-1.gallic acid), and flavonoids 52.74 for LKE, 54.31 for LEE, 72.74 for SKE, and 67.21 for SEE (mg.g-1.quercetin) were determined. The allelopathy of the P. meridionale extracts against L. sativa was confirmed through negative effects on L. sativa seed germination, radical growth and morphology, dry mass, and the concentrations of α-amylase (EC 3.2.1.1), ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6), and polyphenol oxidase (EC 1.10.3.1). It was likely that the allelopathic action of the P. meridionale extracts was related to its effects on the membrane permeability and oxidative stress of the treated L. sativa seeds. The P. meridionale extracts contained saponins, calcium oxalate crystals, and flavonoids, including phenolic compounds, which are known allelochemicals with herbicidal activities.
Highlights
Knowledge about the mechanisms of action caused by secondary metabolites, physical-chemical characterization and biological tests of botanical products facilitated the development and industrial use of products, including medicines, cosmetics, foods, insecticides and herbicides, generated from of native species (Pino et al, 2013).Philodendron meridionale (Buturi & Sakur) is a recently described and non-threatened Brazilian endemic, found in the states of Paraná and Santa Catarina (Buturi et al, 2014)
Most of the control L. sativa seeds germinated within 24 h, whereas most of the seeds treated with high extract concentrations (0.5, 0.75, and 1.0 mg·mL-1) germinated between 24 and 48 h; the effect of the extracts increased as the treatment concentration increased
Interference with the primary root growth of treated plants, as observed in this study, is one of the main indicators used for the study of extracts with allelopathic potential (Souza-Filho et al, 1997)
Summary
Knowledge about the mechanisms of action caused by secondary metabolites, physical-chemical characterization and biological tests of botanical products facilitated the development and industrial use of products, including medicines, cosmetics, foods, insecticides and herbicides, generated from of native species (Pino et al, 2013).Philodendron meridionale (Buturi & Sakur) is a recently described and non-threatened Brazilian endemic, found in the states of Paraná and Santa Catarina (Buturi et al, 2014). Knowledge about the mechanisms of action caused by secondary metabolites, physical-chemical characterization and biological tests of botanical products facilitated the development and industrial use of products, including medicines, cosmetics, foods, insecticides and herbicides, generated from of native species (Pino et al, 2013). Other species of Philodendron have been reported to contain substances with biological activities, including anti-hemorrhagic (Moura et al, 2015), cytotoxic (Hassanein et al, 2011; Ghareeb et al, 2015), insecticide (Santiago et al, 2014) and larvicidal (Alliance et al, 2017). Allelopathy is the influence, beneficial or harmful, of one species of plant on another (Zimdahl, 2018) and occurs when plants release substances (ie, allelochemicals), usually secondary metabolites, which affect the growth and survival of the surrounding vegetation (Bogatek & Gniazdowska, 2007). Substances can work by affecting plant respiration, photosynthesis, enzymatic activity, water relations, stomatal opening, phytohormone levels, mineral availability, cell growth and the structure and permeability of cell membranes and walls (Rezende et al, 2003)
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