Pigmentation in algae:
Ø Algae show great diversity in pigmentation.
Ø Many coloured pigments such as green, red, yellow, and blue have been found in marine and freshwater algae.
Ø Different groups of algae have different and specific pigment composition.
Ø Pigments are usually found in specialized plastids called chromophores in all groups of algae except in the members of Cyanophyceae (blue green algae).
Ø Distribution pattern of pigments has great taxonomic significance in algal systematics.
Ø Classification of algae proposed by Fritsch is primarily based of the pigmentation of algae.
Ø All major algal groups have at least one characteristic pigment in their cells.
Pigments in algae belong to THREE major categories based on their physical and chemical properties.
Ø Chlorophylls are fat soluble green pigments
Ø They are chlorins which absorb blue region and reflect green light
Ø Chlorophylls are responsible for the green colour of algae and other higher plants.
Seven different types of chlorophylls are reported in algae. They are:
(a). Chlorophyll-a (C55H72O5N4Mg)
(b). Chlorophyll-b (C55H70O6N4Mg)
(c). Chlorophyll–c1 (C35H30O5N4Mg)
(d). Chlorophyll-c2 (C35H28O5N4Mg)
(e). Chlorophyll-d (C54H70O6N4Mg)
(f). Chlorophyll-e (C54H70O6N4Mg)
(g). Chlorophyll-f (C55H70O6N4Mg)
Ø Chlorophyll-a : Present in all groups of algae
Ø Chlorophyll-b : Present in Chlorophyta (green algae)
Ø Chlorophyll-c : Present in Bacillariophyceae (diatoms)
Ø Chlorophyll-d : Present in the members of Rhodophyceae (red algae)
Ø Chlorophyll-e : Present in Xanthophyceae.
Ø Chlorophyll-f : Recently discovered chlorophyll from stromatolites, possibly produced by Cyanobacteria
Ø Carotenoids are fat soluble yellow pigments present in algae
Ø Carotenoids are found in close association with chlorophylls.
Ø They protect chlorophylls from photo-damage (solarization)
Ø Chemically carotenoids are tetraterpenoids
Ø Carotenoids are present in almost all algal groups.
Ø Carotenoids with beta-ionone ring have Vitamin-A like activity
Ø All carotenoids are strong antioxidants
Two types of carotenoids are found in algae.
Ø Carotenes are yellow coloured pigments
Ø They are unsaturated fat soluble hydrocarbons
Ø They do not contain oxygen
Ø They absorb blue and green light and transmit yellow and red light.
Ø Examples: α-carotene, β-carotene, and lycopene
Ø Xanthophylls are also called as carotenols
Ø They are oxygen derivatives of carotenes.
Ø Example: lutein and zeaxanthin (both are responsible for the yellow colour of egg yolk)
Ø Phycobilins are water soluble pigments
Ø Phycobilins are always bonded with some water soluble proteins called phycobiliproteins
Ø They are blue and red in colour
Ø They are present in Cyanophyceae and Red algae
Ø Phycobilins are usually found in organisms living in deep water for the efficient absorption of light
Ø All phycobilins are strongly fluorescent
Ø They emit orange or red light after fluorescence.
Two classes of phycobilins are present in algae.
Ø Phycocyanin are blue coloured pigments
Ø They are blue green algae pigments
Ø Phycocyanins are also present in red algae
Ø They absorb green, yellow and red light and transmit blue colour.
Ø Phycocyanins are the principal pigment of Cyanophyceae.
Ø Phycoerythrin are red coloured pigments
Ø Phycoerythrin are red algae pigments
Ø They absorb blue green, green and yellow light and transmit red light.
Ø Phycoerythrin present abundantly in members of Rhodophyceae (red algae)
Distribution pattern of different pigments in different algal groups
Ø All photosynthetic algae contain chlorophylls, carotenoids and Xanthophylls.
Ø Members of Cyanophyceae (Myxophyceae = blue green algae) and Rhodophyceae (red algae) contain large amount phycobilins, particularly phycocyanins.
Distributions of individual pigments in specific algal group are summarized in the following table:
- What are the major pigments of algae?
- What are different types of Chlorophylls present in algae?
- What are carotenoids?
- What are phycobilins?
- What are phycocyanin and phycoerythrin?
- What are green algae pigments?
- What are brown algae pigments?
- What are red algae pigments?
- What Blue Green Algae pigments
- What are the pigments of Diatoms?
- What are the importance of pigments in algal classification and systematics?
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