Characterization of Inhibitory Substances of Tall Fescue on Birdsfoot Trefoil

Abstract

Tall fescue (Festuca arundinacea Schreb.) is known to inhibit the growth of birdsfoot trefoil (Lotus corniculatus L.) seedlings, but the inhibitors have not been identified. Our objectives were to characterize and identify these inhibitory substances. Water extracts of tall fescue herbage were fractionated into anion, cation, and neutral fractions. Paper and gas‐liquid chromatography were used to identify possible inhibitory substances. Birdsfoot trefoil germination and seedling development were inhibited mainly by the anion fraction. At pH 7.0, the anion fraction suppressed root growth by two‐thirds and hypocotyl growth by one‐halL Dilution of the total extract or its anion fraction to one‐third of its original concentration eliminated inhibition of germination, but not of hypocotyl and root growth. Root growth was inhibited more by the inhibitory substance(s) than either germination or hypocotyl growth. Concentration of extracts and low pH of the anion fraction were partial contributory factors to inhibition. Lactic, succinic, malic, citric, shikimic, glyceric, fumaric, and quinic acids plus several unknowns were identified as possible inhibitory substances. Lactic and succinic acids appeared as the major inhibitors.