Phytochrome regulation of endogenous bud development in root cultures of Convolvulus arvensis.

Buds produced endogenously from dark-grown Convolvulus root segments do not elongate more than a few millimeters. Red-light exposures given repeatedly during the culture period induce the buds to elongate and to develop a morphology characteristic of etiolated shoots. Far-red light exposure following each red exposure completely reverses the promotive effect of red light. The role of light in regulating both root geotropism and bud development is discussed as it relates to the developmental pattern of Convolvulus.