Phenolic compounds such as gallic acid, ferulic acid, p-hydroxybenzoic acid, vanillic acid, salicylic acid, tannic acid, and hydroquinone were idntified from the aqucous extracts and volatile substances of tomato plant by paper chromatography, high performance liquid chromatography and gas chromatography.
The seed germination and seedling growth of the experimental species, lettuce and egg plant, were severely inhibited in 5×10 exp(-3) M of phenolic reagents identical to those identified from tomato plant. Germination and growth rate of test species in 5×10 exp(-4) M and 5×10 exp(-5) M were higher than that of 5×10 exp(-3) M. Therefore, 5×10 exp(-3) M of phenolic compounds would be assumed to be threshold concentration for allelopathic effects.
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