Shrinkage early in the day would result from transpirational water losses being replaced from the top of the plant first. Later, losses in this top part of the plant are replaced from lower in the tree. This leads to shrinkage later in the day in the lower part of the tree.
Work Step by Step
Use a sponge as an analogy. Squeeze water out of one end, and it becomes smaller but will re-expand as water moves to that part from the non-squeezed end of the sponge.