Potencial aleloquímico de cumarinas derivadas do eugenol em bioensaios com Lactuca sativa L.

Abstract

Plant bioassays are widely used to evaluate the biological effect of environmental samples, bioactive compounds of plants and/or synthetic substances. To perform these types of experiments, the substrate to be used must be carefully considered. The substrates have a direct influence on biotests, being their physical and chemical characteristics directly related to the development of target plants. In addition, secondary metabolites produced by plants that have an allelopathic effect, such as coumarins, or their laboratory-produced synthetic derivatives, may be less aggressive to the environment when compared to commercially available chemical or synthetic herbicides. This work aims to elucidate the effects of four different types of substrates on the germination and initial growth of Lactuca sativa L., as well as to evaluate the allelochemical potential of synthetic coumarins derived from eugenol on the physiological, cytogenetic and biochemical processes of Lactuca sativa L. For the standardization of the substrates, were used 30 seeds of Lactuca sativa L. cv. Babá de verão in each bioassay, which was composed of filter paper, agar (6 g.L-1), vermiculite and organic substrate Mococa®. For allelochemical action of coumarins, each coumarin was suspended in agar (7 g.L-1) + 8% de Tween 80 to obtain the stock solution of concentration 800 μg.mL-1, from which the concentrations of 50, 100, 200 e 400 μg.mL-1 were obtained. Experiments were performed to verify its activity on germination, initial growth, chromosomal complement behavior and enzymatic antioxidant metabolism of the biotest. For the standardization of substrates, vermiculite provided the greatest growth of the seedlings, being therefore the most indicated, considering the bioassays in which it is not necessary to evaluate aspects of germination, due to the fact that it is possible to evaluate only emergency aspects. In cases where it is essential to evaluate germination aspects, agar is the most suitable substrate, since it has provided considerable growth of the seedlings. To evaluate the allelochemical effect of coumarins, it was verified that the six synthetic coumarins evaluated presented allelochemical action, that is, they interfere in the germination and initial growth of Lactuca sativa seedlings, being the coumarin C1 the molecule with greater allelochemical potential for promoting drastic redution of many parameters. In addition, coumarin C1 has influence on the cell cycle, reducing the mitotic index and increasing the frequency of chromosomal abnormalities; however, did not promote oxidative stress on Lactuca sativa.