Transportation is a vital process in plants. The process involves the transportation of water and necessary nutrients to all parts of the plant for its survival. One of the major factors that are concerned in case of plants is the transportation of water and its termination depending upon the growth.
To overcome this limitation the plant uses several process namely Absorption, Utilization of water, Storing and Translocation. Transportation occurs in three levels in case of plants:
- Transportation of substance from one cell to another.
- A long distance transport of sap within phylum and xylem.
- The release and uptake of solute and water by individual cells.
In the case of active absorption, water moves through symplast and it is absorbed according to DPD changes. The rate of absorption is slow. It comprises of Osmotic and non-osmotic forces. The rate of absorption does not significantly depend on humidity and temperature. It mainly depends on humidity and temperature. The force required for the absorption of water mainly generated in the root cells itself. There would be a decrease the rate of water absorption if the metabolic inhibitors are applied.
The rate of absorption is fast. It occurs in rapidly transpiring plants. The movement of plants is mainly through apoplast and it is absorbed due to transpiration pull. This transpiration pull is created due to the tension created in xylem sap. The rate of absorption significantly depends upon the rate of transpiration. The force required for the absorption of water mainly generated in the mesophyll cells.
Means of Transport
There are three means of transport in plants. They are stated below:
- Facilitated diffusion
- Active Transport
Diffusion: It is a process that involves the passive movement of a substance from cell to cell or from one part of the plant to the cell. They do not involve in the movement of molecules takes place in random fashion and in the expenditure of energy. It is a slow process.
Here the substance moves from higher concentration region to lower concentration region. The diffusion is the only means of transport for gases in case of plants. The rate of diffusion depends on the temperature, pressure, and mainly on a gradient of concentration.
The gradient is a vital component of the process of diffusion. Hence smaller substance have to be diffused faster when compared to large ones. Facilitated Diffusion is a passive process that comprises of Antiport, Uniport, and Symport. Airport Proteins exchange to solute by transporting one out of the cell and one into the cell. The main function of uniport protein is to carry single solute across the membrane. Symport proteins transfer two different solutes simultaneously in the same direction.
Active transport pumps molecules against the concentration gradient. Here the energy of ATP is used to drive the pump. The following figure illustrates the active transport in the cell:
First ATP denotes a phosphate to a particular gateway molecule than it pumps the desired molecule across the membrane.
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