The release of a chemical by a plant that inhibits the growth of nearby plants and thus reduces competition. For example, pines (Pinus) produce substances that kill any seedlings of the same species (autotoxicity or autoal-lelopathy) growing too close to the parent plant. Allelopathy may also be indirect, if one plant inhibits the growth of a second plant or microorganism that itself is essential to the growth of a third plant. Allelopathic substances have been shown to be responsible for various changes during plant successions. For example, in a field succession the pioneer weed stage is replaced by annual grasses because the weeds produce substances inhibitory to other weeds. In arid or semiarid habitats the allelopathic substances are often volatile terpenes released from the leaves. For example, in the Californian chaparral aromatic shrubs, such as Artemisia and Salvia, release oils (e.g. camphor) that inhibit the germination of herbaceous plants. In wetter areas various phenolic compounds have been shown to be allelopathic. See also phytoalexin. |
