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explain the role of xylem and phloem in transportation in plants

Dear Student,

Function of Xylem 

The transportation of water and minerals in plants take place by these steps:

Absorption by roots: The cells of root hairs absorb water and mineral salts dissolved in water by active and passive absorption.

Root pressure: After the absorption by root hairs a pressure is created by the roots that push the water into the xylem vessels. In small herbs and shrubs this root pressure is sufficient to send the water to the tip.

Cohesive and adhesive force: These are the additional forces that help water flow through xylem in upward direction. The force of attraction between water molecules are known as cohesive force and the force of attraction between water molecule and cell walls is adhesive force.

Transpiration pull: It is an anti gravitational force created due to transpiration or water loss from the leaves which pulls up water from the roots. In tall trees transpiration pull helps to draw water to the tips.


Function of Phloem

Food synthesized in the form of sucrose, amino acids is transported by translocation in the phloem. the food enters the sieve elements and can flow bidirectional. One of the major hypothesis of phloem transport is pressure theory according to which water containing food molecules flows under pressure from low to high pressure. This pressure is created by transpiration pull or by turgor pressure that builds between source and sinks. Both forms pressure which leads to transport along the gradient by osmosis. Also, 

Phloemtransports food materials from the leaves to different parts of theplant body. The transportation of food inphloem is achieved by utilizing energy from ATP. As a result of this,the osmotic pressure in the tissue increases causing water to moveinto it. This pressure moves the material in the phloem to thetissues which have less pressure. This is helpful in moving materialsaccording to the needs of the plant. For example, the food material,such as sucrose, is transported into the phloem tissue using ATPenergy.

 


You will learn more in your subsequent classes. 


Hope this information will clear your doubts about the topic.

If you have any more doubts just ask here on the forum and our experts will try to help you out as soon as possible.

Regards
 

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Xylem and phloem. ... Xylem tissue is used mostly for transporting water from roots to stems and leaves but also transports other dissolved compounds. Phloem is responsible for transporting food produced from photosynthesis from leaves to non- photosynthesizing parts of a plant such as roots and stems.
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My ans is bit lengthy but it is correct
Plants, like us, need food and water to survive. We have a heart, arteries and veins that help us circulate our blood around. But plants don't have that and need ways of transporting water and food, which they do through xylem and phloem. Both xylem and phloem are long continuous tubes made by rows of cells. Water is absorbed by plants through the roots, and it needs to be transported from there to the rest of the plant. The xylem, a long tube, moves water and solutes, from the roots all the way to the leaves. This process is called transpiration. Plants need glucose and amino-acids for survival. Plants make glucose in the leaves with photosynthesis and it is converted in sucrose. The phloem, also a long tube, moves sucrose and amino acids from the leaves all around the plant. This process is called translocation. 

The xylem and phloem are arranged in clusters called vascular bundles. They have a specific arrangement, which is slightly different in the roots to the stems. The xylem is made up of dead cells containing lignin - a woody material that makes the walls thick and stiff. This makes xylem impermeable to water and allows it to transport water. Xylem moves the water upwards - only one way, from the roots to the leaves by transpiration. Transpiration is the evaporation of water from the leaves and stems of the plant. Imagine a long string of beads - this is how water droplets stick to each other and move up the plant in the xylem. When this water evaporates out of the leaves, a suction pressure is created pulling the rest of the water through the plant. This pull is called the transpiration pull. On the other hand, the phloem is made up of living cells which have "end walls with perforations". Phloem transport sucrose and amino-acids both up and down the plant, depending on where they are needed via translocation. The leaves, that produce sucrose and amino acids are called "sources" and the places they are delivered are called "sinks". Active transport (means it uses energy) pushes the sucrose from the leaves into the phloem against the concentration gradient. 

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