Botany : Water Relation, Diffusion, Osmosis

BOTANY

Water relation   

1.       Diffusion: Diffusion is the movement of ions, molecules of gases, liquid, and solids from a region of higher concentration to lower concentration due to their random kinetic motion so as to get evenly distributed throughout the available space.

2.       Diffusion pressure :- The pressure exerted by the tendency of the particles to diffuse from the area of its higher concentration to the region of its lower concentration is called diffusion pressure

3.       Diffusion pressure deficit:- It is the amount by which the diffusion pressure of a solution is lower than that of its pure solvent.

Pure solvent has maximum diffusion pressure. Addition of solute decreases the diffusion pressure of solvent.

4.       Significance of Diffusion:-

i.    Transpiration in plant takes place due to the diffusion of water molecules from wet plant interior to comparatively dry atmosphere.

ii.   During photosynthesis and respiration exchange of oxygen and carbon dioxide gas takes place by diffusion.

iii. Diffusion helps to transport the substances within the cell and between the cells.

iv. Salts and ions are absorbed by plant by the process of diffusion.

v.  Aroma of flower spread due to diffusion of volatile aromatic compounds. This helps to attract pollinating insects or agents.

vi. Diffusion is the means of spreading of ions, molecules, and other important substance throughout the protoplasm of the cell.

vii.    Some of the products of digestion in animals are absorbed from ileum by diffusion.

5.       Osmosis:- It can be defined as the movement of solvent molecules or water molecules from a lower concentrated solution(hypotonic) to a higher concentrated solution(hypertonic) when they are separated by a semi-permeable membrane.

6.       Significance of Osmosis:-

i.    Entry of soil water into root is carried out by osmosis

ii.   Cell to cell movement of water is brought about by osmosis

iii. The turgidity of living cells is maintained due to the osmotic entry of water.

iv. Osmosis regulates the guard cell movement in plants due to tugor changes and so regulates the opening and closing of stomata.

v.  Many plant movements like drooping of leaves in Mimosa are brought about by osmosis.

vi. A high osmostic pressure helps to protect plants against drought and frost injury.