Researchers have uncovered a surprising mechanism that allows plants to carefully coordinate the formation and growth of new leaf parts. The study shows that the hormone auxin regulates different phases in organ formation by oppositely affecting the activity of another hormone, gibberellin, to trigger the formation of new leaf structures before reversing course and boosting gibberellin to drive their expansion. The findings offer new insight into how plants build complex organs and could eventually help scientists develop crops with improved growth and architecture.

A plant's ability to produce leaves, flowers and other organs depends on precise location and timing. It must first determine where a new structure will form before allowing it to expand. Now, researchers have uncovered the molecular switch that coordinates these two steps, revealing how plants carefully alternate between putting on the brakes and stepping on the accelerator during organ development.