Plants make their own food by taking in carbon dioxide from the air, minerals and water from the soil. They release oxygen and water vapour, and the process is termed photosynthesis. Plants get energy from the food to perform the vital activities. Food and water is transported to various cells in the body.
The transportation process
Plants take in water through their roots. All roots have a root cap to protect the tender root tip from getting damaged by the soil particles. When the plants grow, the roots branch and rebranch and get fixed in the soil. At the roots tips, there are a large number of cells that absorb water and nutrients from the soil. The amount of water absorbed is proportionate to the number of root hairs. As the number of root hair increases, the surface area also increases, and the plant absorbs more water and minerals.
Xylem and phloem
There are pipe-like vessels in plants through which water and minerals enter. Each vessel is made up of thick walls and elongated cells.
A tissue is a group of cells that performs a specialised function in organisms. These are commonly known as conducting tissue. The conducting tissues are of two types. They are xylem and phloem. These tissues form a continuous network within the plants, and spread across the roots, stem, branches and leaves. The xylem carries water and nutrient minerals from the roots to the leaves. The phloem carries food from the leaves to various parts of the plant.
Transportation process – An example: The functioning of cells in potato:
Peel a potato, cut it into two pieces and slice its bottom
Make a deep hole on the top part of the potato and make a potato cup.
Put some sugar solution in the cup.
Make a note of the level of the sugar. Pierce the outer wall of the potato with a pin.
Place the potato in a container with water in such a way that it is partly immersed in water. Leave it undisturbed for some time. Now observe that the level of the sugar solution increases. This is because water moves from glass beaker (low concentration) to potato (high concentration).
By the force of suction, water and nutrients are transported to all parts of a plant. Water and minerals reach the leaves and use only a small amount to make food. There are small pores, called the stomata, on the lower surface of the leaves through which excess water is released in the form of water vapour. The process of releasing water vapour from the leaves into the atmosphere through the stomata is called transpiration.
Transpiration increases the moisture content in the atmosphere and cools the surroundings. Suction develops in the plant when water from the leaves is lost in the form of water vapour. This force is used to absorb more water and minerals. The suction force is also known as the transpiration pull. It is strong enough to draw water even in tall trees.