(a) Why is transport of materials necessary in an organism (plant or animal)?
(b) What is the need for special tissues or organs for transport of substances in plants and animals?
(c) How are water and minerals transported in plants?
(d) How is food transported in plants?
(a) Transport in organisms (plants and animals) is necessary as it absorbs all essential substances and transports them to all parts so that they reach each and every cell of the body.
(b) Special tissues and organs are needed for the transport of substances in plants and animals because these tissues and organs can pick up the essential substances like food, oxygen, water, etc. at one end of their body and carry them to all other parts.
(c) Water and minerals are transported to various parts of the plant by xylem tissues called xylem vessels and tracheids. Plants take in water from the soil through the roots. The water containing minerals called cell sap is carried by the xylem vessels to all the parts of the body. The roots have root hairs to absorb water and minerals from the soil by diffusion and then pass from cell to cell by osmosis through epidermis, root cortex, endodermis and then reach the root xylem. The water enters the root xylem into the stem xylem and then reaches the leaves from the petioles.
Diagram to show how water (and dissolved minerals) are transported from the soil up to the leaf of a plant.
(d) Transportation of food in plants: The transport of food from the leaves to other parts of the plant is called translocation. Phloem tissue transports the food from the leaves to the other parts of the plant. The movement of food in phloem takes place by utilising energy. The sugar made in the leaves is loaded into the sieve tubes of phloem by using ATP. Water enters the sieve tube containing sugar which causes high pressure and pushes the food to all the parts of the plant having low pressure. This is how the food is transported according to the needs of the plant.