. Explain Means of Transport in Plants

Best Answer

Means of transport:

(a) Diffusion

i. In diffusion, substances move from regions of higher concentration to regions of lower concentration.

ii. It is a passive slow process that does not involve energy expenditure and is not dependent on a living system.

iii. It is very important to plants since it is the only means of gaseous movement within the plant body.

iv. Factors affecting diffusion rates are gradient of concentration, the permeability of the membrane separating them, temperature and pressure, density of diffusing substance 

Diffusion rate also depends on :

i. Size of the substances - Smaller substances diffuse faster.

ii. Diffusion of any substance across the membrane depends on solubility of substance in lipids - Substances soluble in lipids diffuse through the membrane faster. 

iii. Diffusion rate – Gas > Liquid > Solid

iv. Diffusion pressure- The diffused molecules or ions exert pressure on the substance or medium in which diffusion takes place is called diffusion pressure.

(b) Facilitated Diffusion

i. It is the diffusion of hydrophilic substances along the concentration gradient through membrane transport protein without energy expenditure.

ii. Particles which are lipid soluble can easily pass directly through the cell membrane as it is mainly made of it.

iii. The hydrophilic solutes find it difficult to pass through the membrane. For this membrane possess transport proteins.

iv. This diffusion is very specific as it allows cell to select substances for uptake.

v. It is sensitive to inhibitors.

vi. When all of the proteins are used transport rate reaches to maximum and show saturation.

vii. The proteins form channels in the membrane of molecules to pass through. Some channels are always open; others can be controlled.


(c) Active transport

i. It is uphill transport i.e., against concentration gradient and is faster than passive transport.

ii. It involves pumps (movable carrier proteins) and employ ATP for transport across the membrane.

iii. It reaches to maximum when all proteins pumps are being used.

iv. Carrier proteins are highly specific and also sensitive to inhibitors.





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