Re: What is the function or reddish abaxial leaf surface?

Title: Re: [Aroid-l] What is the function or reddish abaxial leaf surface?
Ferenc,

The reddish color is typically caused by anthocyanin pigments (and the spectrum can run from orangish red through red to purplish red to almost purple). From an article way back in the late 70’s {Lee, D.W., Lowry, J.B., and Stone, B.C. 1979. Abaxial anthocyanin layer in leaves of tropical rain forest plants: enhancer of light capture in deep shade. Biotropica 11(1): 70-77} the understanding is that the pigment layer acts as a reflective surface for the light that has already passed through the photosynthetic tissue, scattering the light back up through the same tissue again, essentially giving the plant in the lower light areas twice the available light, or at least making the light available to the photosynthetic tissue twice. With many of the plants in which these pigments are often seen on the abaxial leaf surfaces, moving the plant into higher light, but not so high that it burns the plant, will cause the new growth to exhibit less of the pigments. Likewise, as the plant grows into higher light, i.e. climbing up the tree into higher light, less of the pigmentation is seen.  In a completely different example that again illustrates the reflective nature of these pigments, a group of plants commonly known as crotons, Codiaeum variegatum (Euphorbiaceae) selections often exhibit dramatic coloration on the upper leaf surface when in full sun, again with varying anthocyanin pigments throughout the color spectrum mentioned above. This protects the leaves that would otherwise burn in the intense light. When any of these selections is  moved indoors into a lower light situation, the new growth will go to an all green leaf, much less interesting. Also you will note if you visit the tropics that there are a good many plants, especially but not only including many ferns, the new growth will emerge and enlarge with a translucent reddish/bronzy cast to the leaf material, not going green until the leaf/frond is close to full sized. This also is those same anthocyanins protecting the developing tissue. Good Growing.

Jonathan


On 4/3/10 7:20 AM, "Ferenc Lengyel" <feri.lengyel@gmail.com> wrote:

What might be the function (if any) of the reddish color of the abaxial leaf surface of some Philodendrons? I have acuired a juvenile specimen of a houseplant (presumably Philodendron sagittifolium or a Holland hybrid) which has leaves colored reddish on the abaxial surface. The undreside of some leaves are more reddish than those of others, but the adaxial surface is always green. I have read that juvenile specimens of Philodendron melinonii and maybe other species has a reddish underside too. Why is it good for the plant to have a reddish leaf surface on the underside? I can imagine that a reddish color could provide protection of leaf tissues from excess sunshine, but I can't see any meaning of it on the underside. 
Ferenc

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