Question

. You observe plant cells living in various conditions using high power on your microscope. Describe what you would expect to see when examining plant cells taken from a high salt environment compared to those from an isotonic environment. What kind of differences do you expect to see?  Why (include osmosis in your explanation)?  

Answer 1

Osmosis is the movement of solvent molecules of water molecules through a selectively permeable membrane from a region of higher concentration to a reason of lower concentration. It is a passive process.

On the basis of movement of water molecules across selectively permeable membrane, a solution can be of three types -

1. A solution is said to be hypotonic if its concentration is less than the solution surrounding it. In such a solution when a living cell is placed, water will enter into the cell and the cell will swell up and is said to be turgid.

If more amount of water enters into the cell then animal cell will burst because the plasma membrane is fragile and they are not protected by a tough rigid cell wall. But in case of Plant cell and the cell will not burst because of the presence of cell wall.

2. A solution is said to be hypertonic if its concentration is more than the surrounding solution.

When a living cell is placed in such a solution, water will exit the cell and enter into the solution. In such case the cell will shrink and is said to be plasmolysed.

3. A solution is said to be isotonic if its concentration is equal to the surrounding solution. In such a solution, there is no net movement of water across the membrane and therefore the cell will not change its shape.

For plant cell

If plant cells are kept in hypertonic solution then water will exit from cells and enter into the solution and therefore the cells will shrink.

If plant cells are kept in hypotonic solution then Water will enter the cells and the cells will swell up but will not burst.

No change in shape of the cell when kept in isotonic solution.

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