CBSE Class 9 Answered
Osmosis is the diffusion of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration. Plasmolysis is an effect of osmosis in plants and bacteria. It is the shrinkage or contraction of the protoplasm away from the wall of a living plant or bacterial cell, caused by loss of water through osmosis.
Plasmolysis is seen in only living plant cells and bacterial cells whereas osmosis occurs in all living cells.
For plasmolysis to occur, cell wall is required in addition to cell membrane. Osmosis requires only cell membrane.
(Plasmolysis only occurs in extreme conditions and rarely happens in nature. It is induced in the laboratory by immersing plant cells in strong saline or sugar solutions to cause exosmosis.)
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