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Plant Pigments

Plants have different things in their cells that enable them to absorb light. The most common ones we find in the majority of plants are Chlorophyll A and Chlorophyll B. Below we will briefly discuss the main pigments found in plant cells and relate them to the light spectrum.

The light spectrum.


There are actually more than one kind of chlorophyll, but not all are present in all plants. In most plants they have at least Chlorophyll A and often chlorophyll B. Other Chlorophylls, which we won't discuss here, are: Chlorophyll cl, Chlorophyllc2, Chlorophyll d.

Chlorophyll's are arranged in something called "photosystems" which are in the thylakoid membranes of chloroplasts. The main function of chlorophyll is to absorb light energy and transfer it to the reaction center chlorophyll of the photosystem.

Chlorophyll a has an approximate absorption peak of 665 Nm and 465 Nm.

Chlorophyll b has an approximate absorption peak of 640 Nm and 450 Nm.

Accessory Pigments

Accessory pigments are other pigments that are also able to absorb light. Chlorophyll a & b are green and are able to best absorb light in the 450 nm (violet-blue) and 650 nm (red) area of the light spectrum. Well, that leaves (haha) the green, yellow and orange parts of the spectrum unusable. This is why plants have extra pigments (colours), in order to take in light from different wavelengths that chlorophyll is not good at absorbing.

Carotene is an orange pigment capapble of photosynthesis. This pigment transmits light energy to chlorophyll. As well as photosynthesis, these pigments also help protect against too much light, photoinhibition.

Phaeophytin a are gray-brown in colour.

Phaeophytin b are yellow-brown.

Xanthophyll are yellow pigments in the carotenoid group. These pigments seem to absorb best at 400-530nm. These are involved with photosynthesis with chlorophyll. Chlorophyll is often much more abundant than xanthophylls, and this is why the leaves are still a green colour. When fall arrives in many countries and the leaves change colour, the chlorophyll "dies back" and the xanthophylls are more apparent in the yellow colour you see (like a maple tree)

-The Xanthophyll cycle is a wondeful skill a plant has. In order to protect itself from absorbing too much light, and thus causing photoinhibition, Xanthophyll cycle converts pigments that do not quench energy into ones that do. When a plant recieves too much light, the xanthophyll cycle changes violoxanthin to antheraxanthin and zeaxanthin which are photoprotective pigments.

Anthocyanin pigments are often red, purple or blue. These pigments have been said to help a plant against light stress and act to help protect a plant from blue-green and UV light. Cacti do not have these, they have Betalain instead.

Betalain These pigments are found in Caryophyllales (cacti and beets for example). They are often a red-yellow-purple colour that is often found in flower colour, but it can also be found in leaves, stems, fruits and roots of these plants as well. It is not really known what the exact purpose of these pigments are.

-Betacyanins are reddish to violet Betalain pigments. They absorb light best at 535 nm.

-Betaxanthins are yellow to orange Betalain pigments. They absorb light best at 480 nm.

In relation to Photosynthesis

It would seem, in my opinion, that given the various pigments, and the areas they are most abundant, that Chlorophyll a & b, and to a lesser extent, the various carotenoids (such as carotene and xanthophyll) would be the most productive in the absoprtion of light for photosynthesis. When applying this to cultivation and artificial lights, it would seem logical to choose lights that peak in the 430-470nm and 640-680nm range, to allow the 2 main chlorophyll types to gather the most energy. Light in the blue spectrum may also be a little stronger to allow the carotenes and xanthophylls to absorb more light as well.