Figure 3. Changes in the GA and IAA content in the stolon tip. GA content is initially high and IAA content is low under non-inductive long day conditions. The stolon is elongating longitudinally (A). The black dotted line represents switch to tuber inductive long days. StSP6A transcript (green arrow) is the mobile signal that reaches the stolon tip. Elongation of the stolon is terminated (B), and GA content drops while IAA content is increased. Tuber swelling is achieved initially by cell transversal division (C) and finally by random cell divisions (D).