Avaliação do potencial citogenotóxico do extrato aquoso de Tecoma stans (Bignoniaceae): uma espécie ornamental, invasora e com ação alelopática

Abstract

Allelopathy refers to the beneficial or harmful effect that one plant can exert on another through the release of allelochemicals. The species Tecoma stans (Bignoniaceae), endemic to Mexico and introduced in Brazil, exhibits high seed production, aggressive invasive behavior, and relevant allelopathic potential. In this context, the present study aimed to evaluate how different concentrations of aqueous extracts from the leaves, flowers, and fruits of T. stans affect germination, root and shoot development, the cell cycle, and the numerical and structural stability of chromosomes in Lactuca sativa. Leaves, flowers, and fruits of T. stans were collected on the UFJF campus, and a crude aqueous extract was obtained by diluting 100 g of plant material in 1 L of distilled water. From this extract, dilutions were made to obtain concentrations of 75%, 50%, and 25%, with distilled water used as the control. The experiment followed a completely randomized design, with four concentrations and three replicates, using Petri dishes containing 50 seeds placed on moistened paper with the respective solutions for each plant part analyzed. Every 18 hours over a period of 72 hours, germination percentage and the lengths of the radicles and hypocotyls were measured. Cytological slides were prepared using the squashing method and stained with 5% Giemsa, with three slides analyzed per replicate under a microscope. The cell cycle, chromosomal alterations, and cell death index were recorded. Means were calculated for each concentration and the control, and data were subjected to analysis of variance, with mean comparisons performed using Tukey's test (p<0.05). The results showed that, for all parts of the plant analyzed, there was a significant reduction in germination rate, root growth, and hypocotyl development. The leaf extract caused a significant reduction in the cell death index. The flower extract increased mitotic activity and showed significant chromosomal alterations and a higher number of dead cells. The fruit extract also increased the mitotic index and chromosomal alterations. All extracts demonstrated allelopathic and cytotoxic potential, while the flower and fruit extracts additionally showed genotoxic potential.