Chlorophylls.
The chlorophylls are oil-soluble. Chlorophyll a (greenish-yellow in solution) is the primary photosynthetic pigment in green plants for the trans�fer of light energy to a chemical acceptor. Light that is absorbed provides the energy for photosynthesis. A green leaf absorbs blue light (mostly at 430nm) and red light (mostly at 660 nm). It reflects the green wavelengths so as to appear green to us. Chlorophyll a, alone, is found in blue-greens and in some red algae. Accessory pigments in photosynthesis transfer light energy to chorophyll a. One of these is chlorophyll b (blue-green solution), found in higher plants and green algae with chlorophyll a. Chlorophyll c is also an accessory pigment found with chlorophyll a in brown algae and diatoms. Chlorophyll d, together with chlorphyll a, is found in some red algae.
Carotenoids.
These pigments are considered as accessory pigments in photosynthesis, when found in chloroplasts associated with chlorophyll, and as color pigments when found in chromoplasts. Carotenoids,
like the chlorophylls, are not water-soluble. They absorb mainly violet and blue light between 400 and 500nm, and they reflect red, orange, yellow, brown, and the green color of avocado fruit. They give color to
carrot roots, tomato fruit, and many yellow flowers.
Carotenoids of red and yellow are revealed in autumn leaves (h, I) after the green chlorophyll pigments begin to break down. This occurs when daylengths start to shorten and cooler temperatures prevail in temperate regions of the world. Carotenes (yellow or orange non oxygen containing pigments) seem to function in the prevention of chlorophyll destruction in the presence of light and oxygen. β-carotene is the most important of the carotines. Xanthophyll pigments are oxygen containing carotenoids. They transfer energy to chlorophyll from light. Some of the xanthophylls include lutein, zeaxanthin, violxanthin, and fucoxanthin, which is found in brown algae.
Phycobilins.
These pigments are water-soluble. As accessory pigments they absorb light and transfer excitation energy to chlorophyll a. The red pigment, phycoerythrin, is found in red algae. The blue pigment, phycocyanin, is present in blue-greens and some red
algae.
Phytochrome.
This pigment plays an important role in
regulating many processes of plant growth and development. Phytochrome is found in two reversible forms.
One form, Pr, absorbs red light (mostly at 660 nm) and reflects a blue-green color. The other form, Pfr, absorbs far-red light (mostly at 730 nm) and reflects a light-green color. The highest amounts of phytochrome are found in meristermatic tissues.
Flavinoids.
These water-soluble pigments accumulate in cell vacuoles. They absorb ultraviolet wave lengths of light. Anthocyanins are phenolic pigments that are found in most fruits and in many flowers. These red-, purple-, and blue-reflecting pigments are seen in the red color of apple (Malus) fruit and geranium (Pelargonium) flowers; the blue of cornflowers (Centaurea) and larkspur (Delphinium); and the red and purple of Fuchsia (l, m) flowers. The function of these pigments can only be hypothesized, but study of plants having
these pigments is useful in determining evolutionary relationships. Flavins often appear to us as yellow or ivory-colored flowers. Some flavins, such a riboflavin
(vitamin B2), act as co-factors in enzyme reactions and some are thought to be receptor pigments in the bending of plants toward light (phototropic responses.
Betalains.
These are water-soluble, nitrogen-containing reddish pigments that are found in only 9 families of the flowering plant subclass, Carophyllidae.
These pigments are water-soluble and found in the vacuoles of cells. Betacyanin appears as blue-violet to red and is found in beet (Beta) roots (n) and red cactus flowers. Betaxanthin pigments reflect yellow, orange, and orange-red.
