Allelopathic activity of Chenopodium ambrosioides L.

Abstract

In the chinampas of San Andrés Mixquic, Mexico, the farmers allow Chenopodium ambrosioides L. to grow only where there are no crops. Previous studies suggest that this plant interferes with the growth of other plants. Given current concerns over pesticide use, it is important to understand the management and chemical properties of certain plant species with allelopathic potential since these species may help lessen herbicide dependency in agriculture. Extracts of C. ambrosioides L. were bioassayed in germination and hypocotyl growth inhibition tests of Amaranthus hypochondriacus L. A volatile active fraction was found. At a concentration of 0.552 μ/petri dish, C. ambrosioides essential oil inhibited germination of A. hypochondriacus by 50%, while the hypocotyl growth of previously-germinated seeds of the same species was inhibited by 50% with 0.509 μ/petri dish. α-Terpinene, γ-terpinene, p-cymene, limonene and ascaridole (1-methyl-4(l-methylethyl)-2-3-dioxibicyclo[2.2.2]oct-5-ene) were identified in the essential oil of C. ambrosioides. Ascaridole was the principal allelochemical; 0.098 μ/petri dish caused a 50% inhibition of A. hypochondriacus germination and 0.216 μ/petri dish inhibited hypocotyl growth of the same species by 50%. Another crop species, Phaseolus acutifolius A. Gray, grown hydroponically, was inhibited significantly with the lowest concentration of C. ambrosioides essential oil tested (0.15 ml/I). With higher concentrations, the primary root died and plant growth was visibly stunted. The management of C. ambrosioides as a means of pest control with allelopathy in the chinampa agroecosystem is discussed.