Allelopathic effects of aqueous extracts of Duranta repens on the germination and early growth of Lactuca sativa and Lycopersicum esculentum

Allelopathy can be efined as any stimulatory or inhibitory effect by one plant on another through production of chemical compounds released into the environment. In this work, the effects of aqueous extracts of Duranta repens fresh, dried leaves and fruit on the germination and early growth of lettuce and tomato were investigated. Aqueous extracts at concentrations of 1%, 2% and 4% (w/v) were prepared and characterized as to pH and osmotic potential. Phytochemical analysis of leaves and fruits was also carried out. Germination parameters consisted of the percentage of germination (PG), speed of germination (VG) and speed of germination index (IVG). Initial growth was evaluated through length (root and shoot) and mass (fresh, dried and water content). Extracts of fresh and dry leaves altered the tomato PG and leaf lettuce and tomato VG and IVG. All extracts affected the root length of the lettuce and tomato, as well as the length of the shoots and mass (dry and fresh) of the lettuce. The phytochemical analysis revealed the presence of saponins and flavonoids. The action of the extracts was disassociated from any effect of osmotic potential and pH, indicating allelopathic activity.