Question

Force developed in cortex of root which pushes water into xylem of root is
A. Root pressure
B. Turgor pressure
C. Osmotic pressure
D. Diffusion

Answer 1

The water is absorbed from soil by roots. Water molecules enter roots by a process called diffusion. This passes through the apoplast and symplast pathway to reach the xylem vessels.

Complete step by step answer:
Diffusion is a process by which particles move from higher concentration to lower concentration freely. It is a passive process and doesn’t require any energy. Water enters the roots from the soil by this process. Once the water enters the root, it enters the xylem vessels by two pathways. They are apoplast and symplast. Here, transport is downhill as the movement is dependent on the gradient. Here the movement of water is according to the osmotic pressure. The pressures developed in a solution due to the amount of solute dissolved in it is called osmotic pressure. Osmotic pressure will be high in solutions having higher amounts of solute in them. Water moves from areas of lower osmotic pressure to higher osmotic pressure. In an apoplast pathway, the movement of water is through the intercellular spaces and cell wall without crossing the cell membrane. Meanwhile, water crosses cell membranes in a symplastic pathway. Water moves from one cell to another through plasmodesmata. Because of this reason, the water movement is slower in the symplastic pathway.
Hence the correct option is C.

Note: The water reaches up to the level of the casparian strip by both apoplast and symplast pathway. It is present in the endodermis. So, in order to cross endodermis, water has to move to the areas that are not coated with suberin. Then it crosses by symplast method.