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Plants of barrel medic (Medicago littoralis Rhode) were grown in a soil-manure-peat mixture in a growth chamber under controlled environmental conditions to determine the effects of leaf maturation and physiogenic spotting ou accumulation of coumestrol. The plants were free of disease and insect pests. Under these conditions, a physiogenic leaf spotting occurred which increased with age of the plants. Coumestrol content of the leaves increased with spotting and age. Very high quantities of coumestrol (in excess of 2,000 ppm) were found in mature, heavily spotted leaves. The effects of leaf age and physiogenic spotting on coumestrol content could not be entirely separated. However, further work showed that coumestrol was concentrated in the spots. Mature leaves with no spots contained less than 10 ppm coumestrol. ‘Vernal’ alfalfa (M. sativa L.) was included in this study as a control. No coumestrol was detected in the leaves of Vernal in the vegetative or early flowering stages. Small amounts (less than 30 ppm) were found in yellowing leaves of Vernal in the green seedpod stage. No coumestrol was detected in the immature or mature reproductive tissues of either barrel medic or alfalfa.
Key Words: Senescence • Plant Phenolics • Coumestrol • Estrogen
2 Formerly Research Agronomist, Crops Research Division, Agricultural Research Service, U. S. Department of Agriculture, at Brookings, S. D. 57008 (now Research Plant Physiologist, Crops Research Division, Bee Research Laboratory, Tucson, Ariz. 85719).
Received for publication October 20, 1967.
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