Class 10 Science - Chapter Life Processes NCERT Solutions | What are the differences between the tra

XYLEM

PHLOEM

Xylem helps in the transport of water and minerals with the help of pressure.

Phloem helps in the transportation of the food with the help of energy in the form of ATP.

Xylem is composed of living and non- living cells. Mainly non- living cells are present, including tracheary elements- tracheids and vessel elements. Xylem tissue also contains xylem parenchyma cells for storage function and xylem fibres for the mechanical function.  

Phloem is composed of mainly four components- sieve tube elements mainly for sugar transport, companion cells carry all metabolic functions of sieve tubes, phloem fibres provide tension strength and phloem parenchyma cells helps in transfer of food also called transfer cells. 

Xylem involves the route from roots to the aerial parts of the plants and then evaporation occurs. Once water is absorbed in the root hair, then goes into the cortex then transports in xylem. Path of the transport in xylem goes through apoplast (transport in the cell walls to the intercellular spaces) and symplast (transport occurs from cell protoplast by the interconnection of plasmodesmata). Movement:- 

Epidermis      →       cortex        →         Endodermis          →         Xylem

Transport of food in the form of organic solutes from one place to another place in the higher plants known as translocation. In this, carbohydrates are translocated from leaves to the roots and then in the storage organs like tubers, bulbs, fruits etc. along to the phloem in the form of sugar (sucrose). They are transported through the sieve elements of the phloem and this translocation needs the metabolic energy to transport the food. 

Uptake of water and minerals from the roots includes root pressure to the leaves and includes positive hydrostatic pressure in the xylem. When the water moves upward to a tall tree, at the top of the tree develops a large tension, i.e, negative hydrostatic pressure is developed which pulls the water and the minerals through the xylem.  

Transportation of food movement involves along the turgor pressure gradient that is induced by maintained gradient of water potential; and the flow of organic solutes takes place from the high concentration to the lower concentration, i.e, from leaves to the roots and the organs. Transportation of food is a downward movement.

One most accepted theory is given for the upward movement of water in the xylem is Cohesion- tension theory also known as transpiration pull. This theory includes high tensile strength and high capillarity.

Transpiration pull includes pull from soil to leaves.

Phloem translocation describes the downward movement of the food from leaves to the roots and the organs of the plants. Several theories have been given to explain this phloem translocation- Diffusion hypothesis, Activated diffusion theory, Electro- osmotic theory, Munch hypothesis etc. And; the most accepted theory is the Munch hypothesis. 

Water and minerals from the plants through the roots then cross the root cortex and pass into the stele (xylem) and move upward to the leaves. And, this upward movement of the water and minerals against the gravitational force from roots to the aerial parts through xylem is known as the ascent of sap.

By using the energy in the form of ATP food in the form of organic solutes loaded into the sieve elements of the phloem vascular tissue and by the process of osmosis water enters in the sieve tubes that raise the pressure in the phloem and then the food is transported to the parts of the plants.

Transportation of water and minerals through the xylem is a passive process.

Transportation of food by the translocation process through the phloem is an active process.