Influência das condições de adensamento em populações de Eichhornia crassipes (Mart.) Solms (PONTEDERIACEAE) sobre o potencial alelopático da espécie

Abstract

Macrophytes are the macroscopic forms of aquatic vegetation, important primary producers, and essential for homeostasis of the environments where they are inserted. However, the occurrence of overpopulations of these plants in reservoirs is becoming an important problem in Brazil, especially in relation to impairment of economic uses of these environments, as caused by imbalances due to the increase of their populations. Water hyacinth [Eichhornia crassipes (Mart.) Solms] a floating macrophyte has high ability to colonize new habitats and ease overpopulations in training, and this benefit may be related to the fact that this species present allelopathic compounds capable of negatively influencing the development plants and microorganisms from the surrounding environment. The aim of this study was to evaluate the allelopathic potential of aqueous and ethanol extracts of leaves and rhizomes / roots Aguapé, occurring in Furnas Reservoir, Alfenas, Minas Gerais State. For this purpose, plants of two populations with different density conditions were divided between leaves and roots / rhizomes were collected. Aqueous and ethanolic extracts were prepared at 5% (w / v), which were diluted in 2.5% and 1.25%, for the realization of germination bioassays and initial growth for seven days, using bioassays as seeds lettuce (Lactuca sativa L.). The germination percentage, germination velocity index, number of normal seedlings, root elongation, fresh weight and dry weight were evaluated. The effect of the extracts on the mitotic index and the presence of abnormalities in the genetic material induced by the extracts in bioassays, bioassays were analyzed in 48 h. Phases of cell division were observed, as well as chromosomal abnormalities. From the ethanol extracts, chromatographic analysis was performed in order to identify compounds that may be related to success in colonizing species. The results showed that both extracts have inhibitory effect on germination, early growth and cell proliferation and this effect was concentration dependent for most of the parameters evaluated. Populations considered very densely packed and rhizomes/roots of both populations showed greater inhibitory effect on the ethanol extract. Chromatographic analysis identified the compounds as alpha-linolenic acid, margaric acid, adipic acid, among others, known in the literature for presenting allelopathic effect against phytoplankton. Differences between plant populations and structures were found, the largest amount of compounds identified in rhizomes / roots and densely population considered. The results suggest the existence of allelopathic effect on water hyacinth and this effect may also occur in nature and is related conditions density.