(2) initiation of differential growth of lateral stem segments, paced
to the east-to-west movement of the light source throughout the
day; (3) a light-independent and likely entrained driver involved
in the reversed differential lateral stem growth during the night
that reorients the shoot apex from facing west to facing east before
sunrise; and (4) a molecular signal or structural change that slows
and stops the movements at anthesis. None ofthese putative mechanisms have been determined.