Photosynthesis, as everyone knows, is the process whereby a plant uses green chlorophyll to turn light into the energy it needs. So, how does Purple Copper Beech photosynthesise…
Purple Copper Beech & Photosynthesise
The answer is that it’s not the greeness of chlorophyll that does the job but its chemical composition. As one expert puts it: “The chlorophyll needed for photosynthesis is hiding within the leaf colour, whether it is purple, yellow or red. We simply can’t see that the chlorophyll is there.”
Leaves get their colour from pigments. These pigments fall into one of three primary classes: chlorophyll, carotenoids and anthocyanins:
Because Chlorophyll absorbs red and blue light, the light reflected from or transmitted through the leaf has little or no red and blue light. To our eyes it therefore appears green. It is by far the most common pigment in the plant kingdom.
Carotenoids absorb blue-green and blue light and so the light reflected from foliage (and roots etc.) with a high concentration of this pigment appear yellow or yellow-orange. They also work with chlorophyll in photosynthesis. Carotenoids are therefore what give modern carrots their orangey colour. But carrots were originally purple (the orange came through hybridisation) because their dominant pigment was…
Anthocyanins absorb blue, blue-green and green light resulting in leaves that appear red or purple. They give us red apples, red grapes, red onions and the Purple Copper Beech. The chlorophyll may be masked, but it is still there. The leaves from Purple Copper Beech can even prove it. If you look closely at one in the shade, you will notice it has a slightly greenish tinge – that’s the chlorophyll.
At low light levels, though, green leaves photosynthesise more efficiently (anthocyanin plays no part in photosynthesis) and that is why Purple Copper Beech, unlike Common Beech, needs full sun even though its leaves do produce more chlorophyll when light levels are reduced.
And that is how Purple Copper Beech photosynthesises – along with other non-green plants.