Detection and Attempted Quantification of Allelopathic Chemicals in Buffelgrass (Pennisetum ciliare) Root Leachates Using Reverse Phase-HPLC

Abstract

Pennisetum ciliare, commonly known as buffelgrass, is an invasive grass that has led to noticeable declines in perennial diversity and abundance. Allelopathy, which describes the exudation of secondary metabolites that result in detrimental effects upon neighboring species, has been implicated as a possible mechanism for buffelgrass' success due to observations that its root leachates inhibit the growth of native plants. Since past researchers have only revealed the identity of the acids present within the leachates (Table 1), I have proposed methods in which to extract and quantify these chemicals by employing reverse phase-HPLC. By comparing retention times with that of standards for the identified allelochemicals, p-hydroxybenzoic, vanillic, syringic, and p-coumaric acid were confirmed in buffelgrass root leachates by HPLC. Using calibration curves, buffelgrass roots were found to consist of 5.801x10⁻³±5x10⁻⁶% p-hydroxybenzoic acid, 3.259x10⁻³±8x10⁻⁶% vanillic acid, 4.940x10⁻³±5x10⁻⁶% syringic acid, and 4.369x10⁻³±5x10⁻⁶% p-coumaric acid, by weight. The detection of the acids demonstrated that these compounds were at a significant enough concentration to be detected, thereby suggesting that they may play a major role in plant interference. By detecting and quantifying phytotoxins in native and invasive plants, the chemicals responsible for inhibiting plant growth could be elucidated, establishing a quantifiable criterion of allelopathy.