PHYTOTOXINS FROM SHOOT EXTRACTS AND ROOT EXUDATES OF AGROPYRON-REPENSSEEDLINGS

Allelopathic constituents of ethylacetate extracts from shoots and roo t exudates of 10-day old Agropyron repens seedlings were investigated. The allelochemicals were identified by GC-mass spectrometry and compa rison of retention times and mass spectra to data of respective refere nce compounds. In shoot extracts the cyclic hydroxamic acids 2,4-dihyd roxy-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 deriv ative 2-hydroxy-1,4-benzoxazin-3-one (HBOA), were found. The concentra tion of major component DIBOA was 0.5 mg g(-1) fr. wt, the concentrati on of DIMBOA was 0.02 mg g(-1) fr. wt. Futhermore maleic, t-aconitic a nd citric acid were found. In order to estimate the allelopathic poten tial 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 ,4-dihydroxy-7,8-dimethoxy-2H-1,4-benzoxazin-3- one (DIM(2)BOA) was detected. Vanillic, ferulic and beta-hydroxybutyri c acid are also phytotoxins released by intact, living quackgrass seed lings.