This aim of this research was to analyse the influence of aqueous extracts of Miconia albicans
(Melastomatacea), Lantana camara (Verbenaceae), Leucaena leucocephala (Fabaceae) and Drimys winteri
(Winteraceae) on the ratio and percentage, root growth in tomato (Lycopersicon esculentum (L.) Karsten -
Solanaceae) and cucumber (Cucumis sativus L.- Cucurbitacea) seeds. Extracts were obtained from species
collected in areas for research and preservation of UFSCar ?Campus?. The bioassays were conducted in
laboratory with different concentrations (0%; 25; 50; 75; 100%) of aqueous extracts of leaves (fresh plant
material) (p/v) where the seeds were bedded using Petri plates with filter paper imbibed with solution-test
5ml and incubated in climatic chamber at 25oC, under constant light. The results of this research have
shown differential toxicity of allelopathic substances among the species according the concentration,
application method and tested species. Tomato was more susceptible than cucumber. Miconia albicans and
Drimys winteri extracts have presented inhibitory effects on tomato and cucumber germination mainly on
root growth of these species seeds. Lantana camara and Leucaena leucocephala extracts produced negative
or positive influence on seeds germination according the specie and the parameter. analysed