The Role of Coumarin in the Growth of Roots of Melilotus alba. Contributions from the Hull Botanical laboratory 365

Abstract

1. Melilotic acid and o-coumaric acid inhibited cell elongation in the Avena coleoptile curvature test. Coumarin had no activity under the conditions employed. 2. All three compounds inhibited root growth of sweetclover and alfalfa seedlings. It is suggested that perhaps neither unsaturation nor lactone configuration is essential for their inhibitory activity. 3. The total length increment of roots of sweetclover and alfalfa seedlings grown on agar containing 5 p.p.m. of coumarin was about 55 and 40%, respectively, of the control. At a concentration of 50 p.p.m. of coumarin the increment of sweetclover roots was further decreased by only about 10%, whereas alfalfa roots placed on such agar did not grow at all. 4. The concentration of free and bound coumarin present in sweetclover roots was quantitatively determined. The average concentration of free coumarin was about 74 μgm/gm of fresh weight. Coumaric acid may account for 20% of this quantity. No longitudinal concentration gradient of coumarin was found in the roots of sweetclover seedlings. The possible role of coumarin as a natural growth inhibitor is discussed. 5. During the imbibition and subsequent periods of leaching of sweetclover seeds, coumarin was found in the leachate in quantities proportionate to the length of leaching time. During a leaching period of 24 hours, about 2 μgm. of coumarin were leached out per seed.