Dyschoriste setigera fast branch

One progressive Dyschoriste setigera stem has grown solitary above the many that remain fairly equal down below. The leaves upon it are decussate, meaning that the opposite pairs succeed each other up the stem at right angles, resulting in four vertical arrays of leaves. The arrays are more distinct when the spacing of the leaves is dense, the internodes short. A new branchlet is starting in picture from a leaf axil low down on the elongated stem.

Such leader‑shoot formation incidents are triggered by hormonal conditions, the capturing of light, or readiness for the next development phase. A stem shoot behaves like this when it “wins” the hormonal and resource competition, allowing it to become the plant’s new “main axis”. Auxin is the relevant hormone produced in shoot tips, allowing for surging ahead.

Leadership is a phenomenon in humans that appears similar to what is happening here in some respects, and hormones may play a role as well. Taking the lead differs much among species (Wikipedia).