Autotoxicity of root exudates from taro

Abstract

Effects of chemicals exuded from taro roots in hydroponic culture on the growth and yield of taro were investigated. Taro plants grown in the nutrient solution without activated charcoal (AC) had significantly lower leaf numbers (90%) and shoot dry weights (67%) than those grown with AC. The corm yield per plant also decreased by 34% in the nutrient solution without AC. The allelochemicals adsorbed by the AC were extracted and analyzed by gas chromatograph coupled to a mass spectrometer (GC–MS). The identified compounds included lactic acid, benzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, vanillic acid, succinic acid and adipic acid. The allelopathic potentials of these compounds were evaluated with taro plantlets as a test material. Results indicated that almost all the compounds were inhibitory to the growth of taro plantlets. But benzoic acid was the strongest inhibitor. All of these suggest that root exudates from the taro plant itself is one of the causes of problems in taro culture.