Monday, May 22, 2017

Why Aren't Trees Black?

If trees were more efficient solar collectors, the leaves would be black instead of green. They'd look more like solar cells, which are black so that they can absorb as much light energy as possible.

James Gurney, River Suir, Ireland, Oil, 8 x 10 inches

The green color that we see is "leftover" light, a wavelength that the tree's solar engine is not able to process.

This so-called "green gap" is caused by the fact that chlorophyll does well harvesting blue and red light. But because of a deficiency in the organic chemistry, leaves are not as good at capturing light in the green range.

Then why is some foliage red? The red color is a sun block for young leaf tissue as it develops in the early spring. Without it, some delicate leaves would burn in the spring sun. Normally that red color of early spring foliage gives way to green thanks to the action of enzymes.



The copper beech—or Blutbuche (blood beech in German)—keeps its red color all year round. That happens because a metabolic disorder interferes with the normal action of those enzymes.

This type of tree probably would have died out in the wild, were it not for the intervention of human gardeners, who like the way red foliage stands out in gardens.

I've adapted these ideas from the book The Hidden Life of Trees
Scientific paper on ScienceDirect
Discussion on Biology website


5 comments:

Susan Krzywicki said...

The red can also be due to a cold spell. The leaves are late to develop chlorophyll. Tender new leaves will have red-rimmed leaves that eventually grow out full-stop green when the weather warms up.

Our world is so embedded with these weird quirks: we see the leftover color, we love how our world looks and think we would find black leaves to be unattractive....I remember reading old science fiction novels that dealt with some of these - worlds were created that were fabulously beautiful and totally "off" from our standards of beauty.

And, even the ideas that all of our perceptions are artificially created constructs - that one I have never wrapped my brain around.

Have a beautiful day, everyone.

Bryn Barnard BIFS said...

Love my copper beech!

GJ said...

Black trees: Yes, but consider what a dreary world it would be. Blackness is all very well, but don't you think it's a touch—how shall I put it?—undifferentiated? gj

Newt said...

I love the pale red spring growth of many oaks. Red new growth is supposed to be especially common with tropical trees.

Being more efficient solar collectors might be un-helpful to plants; as it is, trees and other plants spend a lot of their resources repairing and replacing pigments damaged by the sunlight they are charged with collecting. Presumably there is a point where gathering more light causes more trouble than it's worth (and of course, solar energy is not always the limiting factor in plant metabolism; it's often availability of minerals, CO2, or water, so extra solar energy would go unused if those deficiencies could not be addressed).

Lily Oliver said...

Our world is so embedded with these weird quirks: we see the leftover color, we love how our world looks and think we would find black leaves to be unattractive slope ....I remember reading old science fiction novels that dealt with some of these - worlds were created that were fabulously beautiful and totally "off" from our standards of beauty.