Unexpected shifts in cell populations revise understanding of aging process

If you looked at two snapshots of the same maple tree taken in July and December, you'd see a dramatic change from summer's full green crown to winter's bare branches. What those two photos don't show you, however, is how the change occurred—gradually or all at once? In truth, deciduous trees tend to hold out for an environmental signal—a change in light or temperature—and then shed all their leaves within just a week or two.