Ques.7. Write notes on :
(a) Economic Importance of Blue green Algae
(b) Economic importance of Red Algae.
Ans. Economic importance of Myxophyceae. Some species of green algae with gelatinous matrix including Nostoc are boiled in soup utilized as food. These Algae form much of the plankton eaten by fish and the human beings in turn consume the fish. The growth of these algae in abundance makes the water of lakes or rivers unsuitable for human consumption. Excessive growth of some blue green algae such as Aphanizomenon in lakes resulted in the death of innumerable fish due to depletion of the oxygen supply.
The species of Microcystis and Anabaena may even kill the cattle which drink the water polluted with these algae. These algae cause various liver, heart and lung diseases to the cattle which consume the algae with water, and ultimately they die. The active principle in Microystis is described as a potent neurotoxin. If the species of Oscillatoria are consumed by human being along with water, they cause the symptoms of itching, conjunctivities, blocking of nasal passages and bronchial asthma. The dominance of the blue-green algae possessing the ability for nitrogen fixation particularly in the tropics suggests that these organisms are of considerable importance in maintaining soil fertility.
Nitrogen fixation
Blue-green algae are the only organisms which are capable of performing ‘oxygenic’ photosynthesis and fix nitrogen also. Many of them are efficient nitrogen fixers. The existence of process of oxygenic photosynthesis and N2 fixation in same organism is surprising, since N2 fixation is an anaerobic process, and the enzyme nitrogenase in inactivated by the presence of O2 even in low concentrations. Usually, but not always, N2 fixing bacteria are filamentous organisms that produce a specialised type of cell, called heterocyst, within which N2 fixation occurs.
Economic Importance of Rhodophyceae
(i) The cell wall of red algae contains, certain polysaccharides called phycocolloids, some of which contain, sulphur e.g., Agar-Agar is somewhat like gelatin in that it can make a liquid become solid. It is widely used in preparing solid culture media for growing microorganisms in the laboratory. It is a complex carbohydrate and most living organisms do not possess necessary enzymes for breaking it down. As a result, it has no food value for bacteria or fungi. It is also used by human beings as thickness and binding agents in various food products. Agar-Agar is commercially obtained from Gelidium and Gracilaria.
(ii) The cell wall of red algae contain another biochemical carrageenin which is also used as thickening and binding agent in food products, especially in puddings. Many red algae like Porphyra, Palmaria, Gigartina and Rhodymenia are used as food. Porphyra is cultivated and harvested in shallow seas in Japan as food. Chondrus cripus is employed as a stabliser in food like chocolate milk, puddings etc.
BSc 1st Year Botany Economic Importance of Algae Sample Model Practice Question Answer Papers
BSc 1st Year Sample Model Practice Mock Test Question Answer Papers