Autointoxication of tea (Camellia sinensis) and identification of its autotoxins

The regeneration in old tea gardens is a big problem. To understand its mechanism, the autointoxication of tea was investigated and the phenolic acids and total phenolics in the soil extracts and root exudates were analyzed. The aqueous extracts from different plant parts significantly inhibited the seed germination, root and shoot growth of tea seedlings. The seed germination and seedling growth of tea were also inhibited by the aqueous extracts of rhizosphere soil of tea trees with different ages. the inhibition increased with the growing years. Nine phenolic acids (ferulic, cinnamic, vanillic, p-coumaric, benzoic, p-hydroxybenzoic, caffeic, chlorogenic and gallic) were identified in soil extracts. But the benzoic acids and p-hydroxybenzoic acids were not detected in the root exudates. The soil extraction contained bound or free forms of ferulic, cinnamic, vanillic, p-coumaric, caffeic, chlorogenic and gallic acids. Their concentrations varied with tea tree age. The relative contents of total phenolic acids in the soil extraction increased with the age of tea trees. These results suggested that the phenolic acids accumulate in old tea garden might result in tea autotoxicity and the problem of continuous cropping.