Seed-Germination and Seedling-Growth Inhibition by Aqueous Extracts from Hyptis Rhomboidea

To evaluate the allelopathic potential of Hyptis rhomboide Mart. et Gal (native to tropical America ), the effects of aqueous extracts (0.0125, 0.025, 0.05, 0.1 g/mL ) prepared from stalks and leaves of H. rhomboide were studied on the seed germination and seedling growth of four crops (Brassica campestris, Raphanus sativus L., Oryza sativa, and Lactuca sativa). The results showed that the two aqueous extracts significantly inhibited the seed germination and seedling growth of Brassica campestris, Raphanus sativus L., Oryza sativa at the higher concentrations (0.05, 0.1 g/mL), and emerged positive relative with concentration, whereas the lower concentrations had a positive effect on the seed germination and seedling growth of Lactuca sativa by the leaf extracts. By synthetical effect,both the two extracts caused the four receiver seeds with low promote high inhibit effect. The stalks aqueous extracts showed the greatest inhibition effect on the Raphanus sativus L, the leaf showed the greatest inhibition effect on the Brassica campestris and the maximum allelopathic effect occurred with leaf extracts. The results suggested that stalks or leaves extracts of H. rhomboide may influence the natural crops with in allelopathic y effect via the release of allelochemicals from the aerial parts into the environment. The results demonstrate that the aqueous extracts from H. rhomboide allelopathic potential and should be evaluated as an allelopathic species, presenting a risk or advantage to seed germination and seedling growth of crop or weed plants.