Allelopathic effect of aqueous extracts of Persea americana Mill. on Lactuca sativa L.

Abstract

Allelopathy refers to the ability that a plant has to interfere in the metabolism of another by means of substances released into the environment. The objective was to investigate the allelopathic effects of aqueous extracts of fresh and dried leaves of Persea americana on germination and early growth of lettuce. Extracts were prepared at concentrations of 2, 4 and 8%. Phytochemical profile, pH and osmotic potential were also performed from the extracts. Treatments consisted of four replicates of 25 seeds of lettuce distributed in Petri dishes with two sheets of germitest paper and 5 mL of extract. Germination parameters consisted on percentage of germination (PG), speed of germination (VG), speed of germination index (IVG) and coefficient of uniformity of germination (CUG).  Initial growth was evaluated through length (root and shoot), mass (fresh, dried and water content) and content of chlorophyll (a, b and total). Extracts of fresh and dried leaves affected all parameters examined for germination (PG, VG, IVG and CUG). The extracts also led to reductions in length (root and shoot), in mass (fresh and dry) and in the levels of chlorophyll. The action of the extracts was disassociated from any effect of osmotic potential and pH, indicating allelopathic activity. However, the effects can not be associated to the presence of flavonoids and tannins found in fresh and dried leaves of the avocado, as only qualitative tests were performed for identification.