Monday, May 16, 2005

This may sound like a silly question, but it's been bothering me for a while: how does a tree with red leaves photosynthesize? Posted by Hello
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4 comments:

Nick said...

As I recall from high school biology... Red leaves contain green cholorphyl which allows them to carry on photosynthesis. You just don't see the green because the red pigment in the leaves overwhelms the green.

5/16/05, 11:21 AM
Be said...

Aah - thank you! I don't ever remember this being brought up in school (but then again, the high school years are a loooong time away for me). Was twice presented with this issue over the weekend: first, with a red maple. Second, with this apple (I think) tree.

5/16/05, 11:28 AM
Simon Kenton said...

Nick is right. The anthocyanin obscures the cholorophyll. Present in obverse proportion in normally green leaves, the anthocyanins and carotenes are revealed in the fall when the chlorophyll quits.

Now a question for others: in the midst of an entire golden hillside, there will be a patch of aspen whose leaves show red in the fall. This is quite persistent from year to year. Aspen are a clonal species, so that patch could be a progenitress and her daughters with uniform genetics and a uniform predilection for manufacturing anthocyanin; or it could also be a mineral deposit cropping out right there. What's the explanation?

5/16/05, 11:37 AM
Nick said...

I'm not sure... Simon. I do know that hear in Wisconsin the color of the leaves in the fall is very dependent on the weather.

When the cold snaps hit, the cells where the leaves attach to the branches close off (which is why they fall). If after this occurs, and you get warmer days and nights, the anthocyanins and carotenes become stronger due to increased ability to produce sugars I believe, which results in deeper reds because they get trapped in the leaves.

I don't know if its possible that something else might be affecting certain Aspens in a similar way.

5/16/05, 3:22 PM

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