Question

What happens to plant cells when placed in a hypertonic solution?

What happens to plant cells when placed in a hypotonic solution?

What is the purpose of Koehler illumination?

Answer 1

When plant cells are placed in a hypertonic solution, the water concentration is much higher within the cell as compared to outside the cell. To compensate this and equalize it, water from within the cell starts going outside. Hence the cell slowly loses turgor pressure which keeps the cell contents swollen and in contact with the cell wall. Plasmolysis causes the protoplasm (the living part of the cell) to compress and thus causing the plant cell to shrink.

When the plant cell is placed in a hypotonic solution, the water concentration is much higher outside the cell as compared to inside the cell. To compensate this and equalize it, water from outside the cell starts going inside. it takes up water by osmosis and starts to swell. The rigid cell wall prevents bursting. This state is referred to as a turgid state.

Koehler Illumination is a specimen illumination process that relies on even spreading of the path of light over the field of view as well as adjusting to provide good viewing conditions by focusing the light path. It's main advantage is ensuring that an image of the lighting source will not be obtained at the retina end and hence not interfere with the study of the specimen. It does so by using different planes such that the aperture plane makes a diffused image on the retina.