Just curious because I've seen coral red colloring on vine maples out in the sun in a clearcut, yet olive green throughout on the maples still in the shade under the forest canopy. I'm trying to get a handle on red or coral colorings in maples and possible other plants.
Anyone know, what is the coloring of an "Autumn Moon" maple if kept in shade 24/7?
In maples it is anthocyanin that gives leafs the coral red colorings. It is a pigment that protects the photosynthetic apparatus from becoming overloaded and damaged. There is no need for it in shade, so even normally red leaves turn greenish. However, it you take a shade adapted vine maple, say, and then put it in full sun, the leaves will turn a brilliant coral red. Here, in my area, it is usually cool and cloudy in the spring, so the leaves are adapted to those cloudy conditions. Then, by late May we usually get a string of cloudless days and maple leaves in full sun are suddenly ODed on sunlight and get a flush of redishness - anthocyanin - that persists.
Acer shirasawanum 'full moon' aurem strangely lacks this capacity to redden and this, I think, is the principle reason it needs some protection. Autumn moon, on the other hand, has the capacity and can be kept in full sun, but will be green in shade.
There is also protective xanthophyls which give leaves yellow coloring. Unlike anthocyanins that are located in tissues over the photocenters, xanthophyls are incorporated into the photocenter itself and divert electrons away from the thylakoids. Alpine conifers load up on xanthophyls going into fall to protect the chlorophyl through the winter. This is why Japanese white pine needles, for example, are yellow in winter. 'Full moon' aurem has a high level of xanthophyls which is part of why the foliage is a luscious limy green.
... very simplistically speaking.