In this article we will discuss about the Characters and Economic Importance of Algae.
Characters of Algae.
1. Algae are usually aquatic, either marine or fresh water. Only a few algae occur in moist terrestrial habitats like tree trunks, wet rocks, moist soil, etc.
2. Plant body is thallus (a form without any differentiation into root, stem and leaves) which may be unicellular, colonial, filamentous, parenchymatous or pseudo parenchymatous.
3. Algae, like other aquatic plants, are covered over by mucilage. Mucilage protects the algae from epiphytic growth and decaying effect of water. It also prevents desiccation if the algae happen to get exposed on the shores during low tide.
4. Vascular tissues are absent. Being aquatic, water conduction is not required. Some of the giant algae do have a system for conduction of food. The same is not needed in other algae because of their small size and presence of photosynthetic cells all over the body.
5. A mechanical tissue is absent. The body is flexible. It helps the algae to sway with water tides without being torn.
6. Nutrition is photosynthetic. Grana are absent in chloroplast. Algae contain chlorophyll a, carotenes and xanthophyll’s. Additional pigments like phycobilins, fucoxanthin occurs in specific groups.
7. Vegetative and asexual modes of reproduction are abundant. Asexual spores are of two types, mitospores and meiospores. They are easily dispersed in aquatic habitat actively if motile and passively by water currents if non-motile.
8. Sexual reproduction is absent in blue-green algae. In others, it is present. Sex organs are non-jacketed and one celled called gametangia. Sexual reproduction involves isogamy, anisogamy and oogamy in different groups.
9. An embryo stage is absent.
10. Life cycle is various— haplontic, diplontic or diplohaplontic.
Algae are usually differentiated on the basis of their pigments, flagellation and storage products. Algae included under kingdom planate by Whittaker (1969) are of three types— red algae, brown algae and green algae.
Economic Importance of Algae:
Some 70 species of marine algae are used as food, e.g., Porphyra, Laminaria, Sargassum, Ulva.
2. Food Supplements:
Chlorella (green alga) and Spirulina (blue green alga) are rich in proteins. They can be used as food supplements even by space travellers.
Nearly 50% of total carbon dioxide fixation or photosynthesis of the world is carried out by algae. Photosynthesis releases oxygen in the immediate aquatic environment. It is essential for respiration of aquatic life.
4. Primary Producers:
Algae are primary producers of food in large bodies of fresh, brackish and sea waters. This form the basis of food cycles of all aquatic animals.
5. Phycocolloids (Hydrocolloids):
(i) Agar from Gelidium and Gracilaria is used as a culture medium, canning of fish and meat, sizing of textiles and paper,
(ii) Algin from Laminaria, Fucus and Sargassum is used in stabilising emulsions (shaving creams, shampoos, ice creams, jellies) flameproof plastics, security glass and artificial fibres,
(iii) Carrageenin from Chondrus is emulsifier and clearing agent.
6. Sewage Disposal:
Chlamydomonas, Chlorella, Scendesmus, etc. are algae of sewage oxidation tanks which provide aerobic conditions for disposal of sewage by decomposer organisms.