Germination measurements to evaluate allelopathic interactions

The search for new technologies to control weeds is stimulating studies on the action of allelochemicals on seed germination, since many secondary compounds produced by plants are potential source of active principles for formulation of new herbicides. The aim of this paper was to test the extracts of leaves and bark of Copaifera langsdorffii on achene germination of Bidens pilosa, using some mathematical expressions and statistical methods to measure this effect. The aqueous extract of leaves (1:10), bark total alkaloids fraction (62.5, 125, and 250 mg mL⁻¹), and water as control were applied in a Typic Acrustox soil where achenes of B. pilosa were sown. Germination was recorded every six hours, based on embryo protrusion. The total alkaloids fraction at 250 mg mL⁻¹ significantly reduced the germinability and the rate, increasing the time and asynchrony of germination. The results show C. langsdorffii as promising source of natural inhibitors of the germination.