Richard A. Cone

“It’s not just breaking down because it’s old and getting cold,” Spicer said. “It’s being deliberately broken down. Because it is precious.” Spicer explained that every molecule of chlorophyll contains four atoms of nitrogen. If the maple tree in the Arbo simply dropped its leaves in the fall, it would have to make a huge effort in the spring to gather a fresh supply of nitrogen from the soil, which it would then have to pump up from its roots to its branches. Instead, the tree spent the autumn carefully dismantling its chlorophyll into molecular parts, which it moved down little tunnels from the leaves into the branches. There the parts would spend the winter in safekeeping, ready to be quickly moved into new leaves in the spring and reassembled into fresh chlorophyll. It was a smart strategy”
― Carl Zimmer, Life's Edge: The Search for What It Means to Be Alive