INHIBITION OF RADISH GERMINATION AND ROOT-GROWTH BY COUMARIN AND PHENYLPROPANOIDS

Thirteen natural and synthetic phenylpropanoids as well as coumarin (2 X 10(-4) M) Were tested for their biological activity on radish germination and subsequent root growth in light and darkness. Coumarin was the most potent inhibitor. With some exceptions, phenylpropanoids with a carboxylic group in the side chain inhibited root growth. Coumarin was formed spontaneously by photooxidation of 2-hydroxycinnamic acid. Microscopic observations of root treated with coumarin suggest that this substance inhibits the elongation of cells of the differentiating zone of the root.