A) Spirogyra
B) Ulothrix
C) Nostoc
D) Anabaena
Correct Answer: A
Solution :
Cell wall of Spirogyra surrounds the protoplast and is protective in function. Cell wall consists of two concentric layers. The inner is cellulosic in nature and external is made up of pectose, whose outermost portion changes into pectin. The latter dissolves into water to form slimy sheath. This mucilage sheath is referred to as the third layer of the cell wall, which makes its filaments slippery to touch. Ulothrix is a common, freshwater, thread like alga found in cold flowing water. Cell wall of Ulothrix may be thick and lamellated or thin and homogeneous. It consists of two concentric layers, inner and outer. Inner layer is cellulosic and outer layer consists of pectic substance chiefly. Protopectin, which is insoluble in water. The cell wall of blue-green algae shows granular structure. Its principal constituentsare glucosamine, diaminopimelic acid, amino acids and muramic acids with some amino sugars. Cellulose is absent, eg, Nostoc, Anabaena.
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