Day‐length as Related to Vegetative Development in Ulexeuropaeus I.

Summary Seedling development, especially in respect of the ‘juvenile‐adult’transition, is shown to be far‐reachingly affected by day‐length. Extension of high‐intensity, short‐day illumination with sub‐compensation‐point light affects leaf and branch ontogeny both qualitatively and quantitatively. It is suggested that the changes affecting vegetative growth that go on during the low‐intensity light phase are of a formative nature, and that they may be more fundamental, in a general metabolic sense, than photoperiodic reactions (flower‐inducing) sensu stricto.