"Cell physiologists have found a world inside an autumn leaf that resembles the pandemonium on a sinking ship. Metabolic pathways start to fail. Compounds break apart. Doomed cells rush to salvage the valuables, especially nitrogen, by sending them off to safer tissues. So in this final crisis, why make a special effort to turn red? Does the red-making machine turn on by accident, or do the red pigments contribute something valuable? Why would passengers fleeing the Titanic stop to repaint their staterooms?...
In the 1990s, other researchers also explored the idea of red pigments as sunscreen. Debate bloomed over how to devise a test that avoids confounding factors, such as different rates of photosynthesis in different-colored leaves...
the aging leaf has to salvage as much nitrogen as possible and send it to tissues that will survive the winter. So, as decrepit as the photosynthetic mechanism becomes at the end, it has to keep catching and processing sunlight if the leaf is to finish the salvage operation...
Gould's lab made a movie. The researchers filmed the stabbing of both the all-green and the red-splotched leaves of P. colorata. In the October Plant, Cell and Environment, Gould and his colleagues report seeing an oxidative burst of hydrogen peroxide a minute or less after they pushed the needle into the upper layers of leaf tissue. In red tissues, the burst faded quickly. In green ones, however, it intensified...
A suggestion for yet a third function for anthocyanins in leaves comes from physiologist Linda Chalker-Scott of the University of Washington in Seattle. She proposes that the pigments regulate water movement. "
FB: oh, so this is why you kinda see a color gradient in trees "In fall, leaves bathed in brilliant sunlight turn red, but shaded leaves don't develop anthocyanins and so just turn yellow. The red leaves recovered faster from flashes of intense blue light, the researchers report in the October Plant Physiology."
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