Allelopathic Activity of the Water Extract of Aloe (Aloe vera L.) and mint (Mentha SP.) on lettuce (Lactuca sativa L.)

Abstract

Possible allelopathic activity of water extracts of the medicinal plants aloe and mint on the germination and initial growth of lettuce is evaluated. Extracts were prepared from an initial solution at 20% (weight/volume) of fresh leaves. Solutions at concentrations 25 and 50% were dosed from the crude extract taken as 100%; distilled water (0%) was used for control. Germination and growth tests for lettuce seeds exposed to extracts were undertaken by soaking of the substrate paper. Germination biotest showed the following parameters: germination percentage and germination speed index after 5 days evaluation. Plantlets with 2 days of germination were exposed to different treatments to evaluate the effects of extracts on growth. Length and fresh and dry biomass of the aerial part and root were evaluated. Assays were kept in a BOD-type germination chamber for a 12-h photoperiod, at 25°C. Water extracts of mint and aloe did not affect germination percentage of lettuce seeds but germination speed index was negatively affected. Extracts delayed the germination process. Extract of both plants stimulated the growth of lettuce plantlets and extracts had an apparent allelopathic activity on the target plant.