TRANSPORT IN PLANT

Ø Transport in Plant can be occurred by the following methods

1. Diffusion:-

·         Transport of water, minerals, organic nutrients and growth regulators over a small distance i.e. cell to cell called diffusion.

·         In diffusion no expenditure energy takes place because the substances moving from the higher concentration to the lower concentration.

·         Diffusion is a slow process i.e. molecules move about 50µm in 2.5 seconds and doesn’t depend on living system.

·         Diffusion is obvious in gases and liquid but in solid it is more critical.

·         Diffusion is the most important in the plant because there is no any system is present for gaseous exchange.

·         The rate of diffusion is affected by the followings.

1.       Concentration gradient.

2.       Permeability of membrane.

3.         Temperature.

4.       Pressure.

2. Facilitated Diffusion:-

·         We all know that diffusion depends on the size of substances i.e. small substances diffuse faster than large.

·         The substances soluble with lipids are diffuse faster (Because membranes are made of lipids) while the substances which have hydrophilic moiety diffuse very slow so it can be facilitated through the site of proteins of membrane and the process called facilitated diffusion.

·         The rate of transport is maximum when all the proteins are used or saturated.

·         The facilitated diffusion has an advantage to allow the cells to select the substances for diffusion.

·         The protein inhibits the molecules when that reacts with site chain of the transport proteins.

·         Facilitated diffusion also occurs without any expenditure of energy.

·         The proteins have channels some of these channels are always open but some are controlled to cross over through them.

·         Some special proteins are also present in some bacteria, plastids, mitochondria etc. called porins having pores and when substances attached with them then it rotates to cross the substances through membranes.

On the basis of directions, the transports are of different types:-

1.      Uniport: - The single molecules diffuse through a membrane in only one direction.

2.      Symport: - The two different molecules diffuse in only one direction.

3.      Antiport: - The two molecules diffuse in opposite direction at a same time in a through the membrane.

3. Active Transport:-

·         It is the phenomenon where the molecules passes through the membrane with the help of protein the here the transport occurs from the lower concentration to the high concentration with the help of expenditure of energy called active transport or uphill transport.

·         As like facilitated diffusion its rate is maximum when all the proteins are used or saturated.

Comparison between different Transport Process:-

Property	Simple Diffusion	Facilitated Diffusion	Active Transport
1.       Requires special membrane protein	No	Yes	Yes
2.       Highly selective	No	Yes	Yes
3.       Transport Saturates	No	Yes	Yes
4.       Uphill transport	No	No	Yes
5.       Require ATP energy	No	No	Yes

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