Soil Toxicity Induced by Terpenes from Salvia leucophylla

Abstract

The capacity of dry soil colloids to adsorb volatile terpenes from the atmosphere suggests a mechanism for seedling inhibition by Salvia leucophylla. Gas chromatography showed diminishing terpene concentration in air exposed to soil. Fresh soil treated with volatiles from macerated Salvia leaves was shown to be highly toxic when assayed against Bromus rigidus. The soil was shown to retain its toxicity for several months. This suggests the following mechanism for patterning of annual herbs about Californian sage thickets: Toxins which are evolved by Salvia in hot weather are adsorbed by dry soil. Seedling growth is inhibited when adsorbed terpenes are dissolved in the cutin of seedlings in contact with the soil colloids. Other factors such as moisture conditions and animal activity may contribute to the observed patterning.