High-performance liquid chromatographic analysis of a crude extract of Alternaria brassicae gave three compounds affecting plant growth. Based on spectral analyses, these compounds were identified as N-methyl-2,5 dimethyl-N'-cinnamoylpiperazine, 2-hydroxy-l'-methylzeatin and 3-carboxy-2-methylene4pentenyl4butenolide. Treatment of seedlings of canola/rapeseed with N-methyl-2,Sdimethyl-w-cinnamoylpiperazine and 3-carboxy-2 methylene4pentenyl-4-butenolide reduced their growth whereas 2-hydroxy-1'-methylzeatin increased the growth of seedlings. Moreover, treatment of canola/rap-eseed cotyledons with 2-hydroxy-l'-methylzeatin increased the chlorophyll content, whereas the other two compounds induced chlorosis.