BIOLOGICALLY-ACTIVE SECONDARY METABOLITES OF BARLEY .2. PHYTOTOXICITYOF BARLEY ALLELOCHEMICALS

The release of alkaloids by barley was quantified by HPLC. Hordenine w as released from the roots of barley in a hydroponic system for up to 60 days. The amount reached a maximum, 2 mu g/plant/day, at 36 days, t hen declined. Effects on white mustard by hordenine and gramine includ ed reduction of radicle length and apparent reduction in health and vi gor of radicle tips. Transmission electron microscopic examination of white mustard radicle tips exposed to hordenine and gramine showed dam age to cell walls, increase in both size and number of vacuoles, autop hagy, and disorganization of organelles. The evidence of the morpholog ical and primary effects of barley allelochemicals at the levels relea sed by living plants indicates that the biologically active secondary metabolites of barley may lead to a significant role in self-defence b y the crop.