question_answer 25)

  Plasmolysis in a plant cell is defined as (a) break down (lysis) of plasma membrane in hypotonic medium (b) shrinkage of cytoplasm in hypertonic medium (c) shrinkage of nucleolus                                            (d) None of the above

Answer:

  When a cell is immersed in hypertonic (very concentrated) solution, water diffuses out of the cell by the process of osmosis. This is because there is a lower concentration of water outside the cell. Although water molecules pass the cell membrane in both direction but more amount of water goes out of the cell than the amount of water which enters it. As a result of this the cell shrinks. This process is called exosmosis. If exosmosis continues in a plant cell, the cytoplasm appears to be shrunken. This is called plasmolysis and the cell is said to be plasmolysed.