EXTRACTION AND IDENTIFICATION OF PHYTOTOXIC SUBSTANCES ACCUMULATED IN NUTRIENT SOLUTION FOR THE HYDROPONIC CULTURE OF TOMATO

Phytotoxic substances were extracted with diethyl ether and ethyl acetate from an acidic aqueous solution prepared by the concentration and acidification of a residual nutrient solution (RNS) for the hydroponic culture of tomato. A similar extraction was also carried out for an eluent with an alkaline methanol solution from the residual activated charcoal (RAC) added to the nutrient solution during the cultivation. Gas chromatography and gas chromatography/mass spectrometry showed that the extract with diethyl ether from RNS contained benzoic, phthalic, sinapic, and palmitic acids as phytotoxic substances and the extract from RAC contained additional organic acids such as 4-hydroxybenzoic, phenylacetic, vanillic, ferulic, caffeic, and 2-hydroxy-3-phenylpropanoic acids.