PHYTOTOXINS FROM SHOOT EXTRACTS AND ROOT EXUDATES OF AGROPYRON-REPENS SEEDLINGS

Allelopathic constituents of ethylacetate extracts from shoots and root exudates of 10-day old Agropyron repens seedlings were investigated. The allelochemicals were identified by GC-mass spectrometry and comparison of retention times and mass spectra to data of respective reference compounds. In shoot extracts the cyclic hydroxamic acids 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one (DIMBOA) and 2,4-dihydroxy-2H-1,4-benzoxazin-3-one (DIBOA), as well as the corresponding lactam derivative 2-hydroxy-1,4-benzoxazin-3-one (HBOA), were found. The concentration of major component DIBOA was 0.5 mg g(-1) fr. wt, the concentration of DIMBOA was 0.02 mg g(-1) fr. wt. Futhermore maleic, t-aconitic and citric acid were found. In order to estimate the allelopathic potential of living plants an investigation of root exudates was performed. The cyclic hydroxamic acids were identified as important constituents. Their concentrations were 0.4 mu mol l(-1) DIMBOA and 0.2 mu mol l(-1) DIBOA. Additionally 2,4-dihydroxy-7,8-dimethoxy-2H-1,4-benzoxazin-3-one (DIM(2)BOA) was detected. Vanillic, ferulic and beta-hydroxybutyric acid are also phytotoxins released by intact, living quackgrass seedlings.