Phytotoxic Substances Involved in Teak Allelopathy and Agroforestry

Abstract

Teak (Tectona grandis L.f.) is one of the most valuable timber species, and is cultivated in agroforestry systems in many countries across the tropical and subtropical regions of the world. The species is also one of the most essential trees in home gardens in South Asia due to its wood quality and medicinal value in folk remedies. It is a deciduous tree species, and the amount of litter that falls from teak trees is huge. The decomposition rate of the litter is relatively fast in tropical humid conditions. The interactions between teak and weeds, or crops, under the teak trees have been evaluated in terms of allelopathy. Evidence of allelopathy is documented in the literature over the decades. The leachate and extracts of teak leaves suppress the germination and growth of several other plant species. Phytotoxic substances, such as phenolics, benzofurans, quinones, terpens, apocarotenoids and phenylpropanoids, in the teak leaves, were isolated and identified. Some phytotoxic substances may be released into the soil under teak trees from leaf leachate and the decomposition of the litters, which accumulate by annual leaf fall and can affect the germination and growth of undergrowth plant species as allelopathic substances. The allelopathy of teak is potentially useful for weed management options in agroforestry and other agriculture systems to reduce commercial herbicide dependency. It was also reported that agroforestry systems with teak enhance income through the production of crops and woods, and provide energy efficiency for crop cultivation.