The Steam

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  • Topic: Water, Xylem, Phloem
  • Pages : 2 (459 words )
  • Download(s) : 71
  • Published : February 13, 2013
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Good morning
Today we will tell u about the transportation of water and minerals in plants. The plants absorb water and minerals from the ground through roots. These nutrients are transported to various parts of the plant like stem, leaves and flowers. The phenomenon of upward movement of water and minerals is called ascent of sap. Only a small quantity of water is used up in metabolic process and growth of the plant. The plants require water and mineral salts for making food by process of photosynthesis and other functions. The process of transportation of water and minerals is done thru a really thin tube which is called the xylem. It works on the law of the capillary action The water and minerals absorbed by roots are conducted upwards to the leaves, flowers and other parts of the plant. It takes place through xylem tubes. The upward movement of sap that contains war and minerals is called ascent of sap. Water, mineral salts and sugar (food) are transported by two methods in higher plants: (1) translocation, which is the movement of dissolved substances from one part of the plant to another, and (2) transpiration, in which water evaporates from the leaves and the subsequent movement of absorbed water takes place through xylem. Water and dissolved salts travel upwards in the xylem vessel, while food passes downwards and upwards in the sieve tubes of the phloem. There are four main differences between xylem and phloem: (1) xylem is dead, where as phloem cells are alive. (2) Xylem carries mainly water and minerals, while organic compounds such as sugar and amino acids are transported to the phloem. (3) The flow of liquid in xylem is upward only, whereas the flow of liquid in phloem is bidirectional. (4) The contents in phloem can move up and down the plant simultaneously. Observations * The mechanism is based on purely physical forces because the xylem vessels and tracheids are lifeless. * Roots are not needed. This was demonstrated over a...
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