How is water absorbed into the roots ? Explain with an experiment.
A. To prove that the water absorbed by root hairs.
Apparatus : Mustard seedlings, Filter paper, Slides, Cover slips, handlens and microscope.
- Take some mustard seedlings which have been grown on wet filter paper.
- Observe the mass of fine threads coming from the seed by hand lens.
- These are root hairs through which water enters the plant.
- Gently squash a portion of the radicle between slide and coverslip in a drop of water and examine under a microscope.
- Note the thinness of the walls of the root hairs. .
- Osmosis plays an important role in absorption of water by root hairs.
- Root hairs grow out into the space between the soil particles and that the hairs are surrounded by moisture.
- The soil water is an extremely dilute solution of salts, more dilute than that of the cell sap in the root hair, therefore water will pass into the vacuole of the root hair by osmosis.
- The entry of water dilutes the contents of the root hair vacuole so that it becomes weaker than its neighbour.