Photoperiodic regulation of axillary bud differentiation in strawberry. Longitudinal sections of non-differentiated (a) and differentiated (b and c) axillary buds. Buds were collected from SD-grown 6-day-old runner tip (a) and SD- or LD-grown 10-day-old runners (b and c, respectively). d: Schematic drawing showing the growth habit of the strawberry runner. Under LD conditions, the axillary bud of the mother plant (Mp) produces a runner, which consists of units of two long internodes and a daughter plant (Dp 1, 2, 3). When the terminal bud of the runner produces a new Dp, the second axillary bud of the runner (Ab2; axillary bud #2) forms the next sympodial unit, continuing the growth of the runner in LD. In SD, runner growth ceases and Ab2 forms a branch crown (Bc). N1, N2 = node 1 or 2; Rm = rib meristem, Rz = rib zone. Scale bar = 200 μm.