Allelopathic effects by Empetrumhermaphroditum on seed germination of two boreal tree species

Indoor and outdoor experiments demonstrated that allelopathy is an important factor explaining seed regeneration failures of Scots pine (Pinus silvestris L.) in forest floor vegetation dominated by the dwarf shrub Empetrum hermaphroditum Hagerup. Scanning electron micrograph views of the leaf surfaces of E. hermaphroditum reveal secretory glands that are shown to be involved in the release of water-soluble phytotoxic substances. Bioassays indicate that low doses and short exposure times of seeds to leachates have strong negative effects on germination and early root development. Activated carbon can eliminate the inhibitory effects of leachates and litter. This technique demonstrates the occurrence of allelopathic interference by E. hermaphroditum on seed germination of both Scots pine and aspen (Populus tremula L.). In a field experiment the allelopathic effects by E. hermaphroditum are strong during early spring when germination and growth initiate and ground ice still is present. Extracts passed through soils collected from an E. hermaphroditum site were detoxified, while those passed through sterilized soil were not. Therefore, microorganisms may detoxify the allelochemicals under some environmental conditions.