Relative Effects of Known Plant Inhibitors on Species from First Two Stages of Old-Field Succession

Abstract

The effects of six phenolic compounds on the growth of seedlings of three species of flowering plants important in old-field succession in central Okla- homa were investigated. These compounds were previously found to be produced by several species from the first stage of such succession and to be inhibitory to bacteria or higher plants. All six compounds, chlorogenic acid, isochlorogenic acid, gallic acid, gallotannic acid, p-coumaric acid, and p-hydroxybenzaldehyde inhibited Amaranthus retroflexus and Bromus japonicus, two species important in the first stage of old-field succession. On the other hand, Aristida oligantha, the dominant in the second stage of succession, was either stimulated or not affected. The concen- trations that caused inhibition were quite low. Chlorogenic acid and isochlorogenic acid were inhibitory to Amaranthus retroflexus at a 0.83 X 10-7M concentration. A 0.83 X 10-4M concentration of chlorogenic acid stimulated the growth of Aristida oligantha seedlings. Previous work in this laboratory indicated that several species of plants from the first stage of succession were very inhibitory to associated species of the first stage but less so to Aristida oligantha. The responses elicited by the pure compounds in the present study correlated well with the effects caused by the plants which produce them. It is possible, therefore, that the rapid disappearance of the first stage in the successional pattern (2-3 yr) is due to the fact that the species involved eliminate themselves by chemical inhibition, and Aristida oligantha invades simply because it is not harmed by the same inhibitors.