Avaliação fitotóxica e citogenotóxica do extrato aquoso bruto de Mimosa Caesalpiniifolia Benth. no biomodelo vegetal Lactuca sativa L.

Abstract

Allelopathy is a natural phenomenon that involves the release of chemical compounds that may have an inhibitory or stimulating action on other organisms. The species Mimosa caesalpiniifolia Benth is considered invasive and with allelopathic potential, so this work aimed to carry out a study on the action of the aqueous extract of this species, at different concentrations, on germination and cell cycle of the plant biomodel Lactuca sativa. From the crude extract, which used 300g of fresh leaves of M. caesalpiniifolia in one liter of distilled water, concentrations of 25%, 50%, 75% and 100% were prepared. For each treatment there were three Petri dishes with 100 lettuce seeds that were protected in DIC, in addition to the negative control, containing water. Every 24 hours, for 72 hours, the seeds were evaluated in relation to the percentage of germination and, after 72 hours of analysis, the germinated seeds had the length of their rootlets measured. In addition, cell cycle progression, manifestations of death and chromosomal aberrations were monitored. Biochemical analyzes of the lyophilized extract and lettuce seeds were carried out in the 72h period (SOD, POD, PPO and CAT enzymes). After the first 24 hours, there was a decrease in the germination rate, and, in the 72-hour period, almost all treatments were equal to the control, except for the 100% treatment, which maintained a lower rate in relation to the control. An analysis of the root length indicated that, after 72h, it was smaller than the control in all treatments and that all concentrations of M. caesalpiniifolia extracts induced a decrease in the mitotic index in the root meristems of L. sativa, in addition to increasing the index of chromosomal alterations in root meristems. The rate of micronuclei showed a difference in relation to the control only in the concentration of 100% at 72h of exposure, while the rate of cell death increased with the increase in the concentrations of the extracts, with a difference in the concentrations of 50% to 100%. Extracts between 50% -100% induced a higher rate of cell death. The presence of a whitish precipitate indicated tannin-gelatin complexation in the sample and, consequently, the presence of condensed tannins. There was no statistical difference between the phenol contents found. In the evaluation of the antioxidant activity by the reduction of the DPPH radical, the results did not show statistical difference. There was no significant difference for superoxidase dismutase. For polyphenol oxidation, there was no difference between the control and the other treatments that there was no difference between them. For catalase, there was no significant difference between the control group and the 25% treatment, but there was a difference between the control and the 25% treatment in relation to the 50%, 75% and 100% treatments, which had no difference between them. In the enzymatic activity of peroxidase, there was a significant difference between the control group, the 25% and 50% treatment and the 50%, 75% and 100% treatments. Thus, it is concluded that the aqueous extract of Mimosa caesalpiniifolia has phytogenotoxic activity on lettuce seeds, delaying germination and compromising root development, causing DNA damage that can lead to cell death.