PHOTOCONTROL OF ETHYLENE PRODUCTION BY LETTUCE SEEDS AND BEAN HYPOCOTYLS

Red light of about 660 millimicrons has been shown to promote the germination of Lactuca sativa var. Grand Rapids seeds and to cause the unfolding of the hypocotyl hook of Phaseolus vulgaris L. var. Black Valentine. In both cases, the effect of red light was reversed by far-red light at about 730 millimicrons. Ethylene promoted the germination of lettuce seeds and caused a negative curvature of bean hooks. Red light stimulated ethylene production from lettuce seeds but it inhibited ethylene production from the bean hooks. Lettuce seed germination and bean hook unfolding seem to be examples in which phytochrome promotes or inhibits the formation of ethylene that, in turn, appears to control the physiological response.