Question

Water rises in plant due to:
A) Capillary
B) Viscosity
C) Fluid pressure
D) Osmosis

Answer 1

To solve this question, it is important to understand the flow of water in any plant is against gravity. Hence, the phenomenon explaining the rise of water should explain how the flow happens against gravity.

Complete answer:
Let us define and understand each of the terms mentioned in the options to understand the right phenomenon.
The Phenomenon of rise in liquid in a narrow thin tube against gravity due to the surface tension between the liquid and wall of tube is called the capillary action. Inside the stem of a plant, there are a large number of fibres which are very thin and small in diameters, these fibres actually carry the water from the root to the different parts of the plant.
Hence this option A is the correct answer.
The resistance between the walls and fluid or between the internal layers of the fluid is called viscosity and hence it is not responsible for the rise of water in plants. Hence, this option is incorrect.
Fluid pressure is a measurement of the force per unit area on an object in the fluid or on the surface of a closed container. This pressure can be caused by gravity, acceleration, or by forces outside a closed container. That’s why it is not responsible for water rise in plants. Hence, this option is incorrect.
Osmosis is the flow of liquid from low density towards the high density through a semipermeable membrane. There is no relation of water transportation in plants with the osmosis. Hence it is an incorrect option.

Therefore, the correct option is Option A.

Note: Always remember that the surface tension is responsible for the capillary action and the rise in height of liquid in a narrow thin tube due to surface tension is given by:
$h = \dfrac{{2T\cos \theta }}{{\rho gr}}$
Where h=rise in height, T=surface tension, g= acceleration due to gravity, r=radius of the tube and $\theta$ = angle of contact and $\rho$ = density of fluid.