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.
