Q.2. Write an illustrated account of the habit, structure and methods of reproduction in Oscillatoria.
Ans.2. Occurrence: The species of oscillatoria are commonly found in fresh water. They are fourth in ditches, ponds, etc. Some species have been reported from hot springs.
Structure: The plant body is filamentous. The filaments are unbranched, cylindrical and uniseriate. The filaments are known as trichomes, they are free and found either singly or in masses. Each trichome consists of numerous cells placed end to end. The trichome does not show any differentiation into base and apex. The filaments are capable of spontaneous movements.
Each cell of the trichome is almost rectangular. Some of the intervening filaments are different in shape and are called separation discs The cell wall consists of cellulose and pectic compounds.
Beneath the cell protoplast is present which is easily distinguishable into peripheral pigmented portion, the chromoplasm and a central colourless region, the central body or centroplasm. The chromoplasm contains the pigments, and reserve food material. There are no definite chromatophores and so the pigments may also be present in the chromoplasm. The central body or centroplasm on incipient nucleus is the nucleus without nuclear membrane. This is an autotrophic algae. (BSc 1st Year Botany Cyanophyta Sample Model Practice Question Answer Papers)
Reproduction: Only vegetative types of reproduction have been reported in Oscillatoria which takes place with the help of hormogone.
In this method, at certain place of the filaments biconcave dead disc are formed known as separation disc. From these places where disc are formed, the trichomes get broken into number of hormogonia. Now, each hormogonium separates and directly gives rise to a new thread (trichome).
BSc 1st Year Botany Cyanophyta Sample Model Practice Question Answer Papers
BSc 1st Year Sample Model Practice Mock Test Question Answer Papers