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Water and ion uptake in plants

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Water and ion uptake in plants

The effect of loss and gain of water in plants respectively. Image credit slideshare.net

The effect of loss and gain of water in plants respectively. Image credit slideshare.net

ZIMSEC O Level Integrated Science Notes:Water and ion uptake in plants

  • When plant cells are surrounded by water, the water enters by osmosis until the cells are full of water.
  • The water enters the plants because there is relatively more water outside the cells than within.
  • These plant cells are surrounded by a strong cellulose cell wall that prevents them from bursting.
turgid_flaccid-min

Plamolysed (flaccid) vs turgid cell with arrows showing the direction of water diffusion. Image credit kshitij-pmt.com

  • When cells are full of water they are said to be turgid.
  • If plan cells are placed in a strong sugar/salt solution they lose water via osmosis.
  • Plasmolysis is the movement of water out of the cells.
  • Plasmolysis occurs because there is relatively more water outside the cells than within the cells.
  • When water moves out of the cells they become soft as the cell walls sag in.
  • When this occurs the cells are said to be flaccid.
  • Plants gain water continuously by osmosis through microscopic root hairs if there is enough water in the soil.
  • Water will only enter the plants if there is a higher concentration outside the roots than on the inside.
  • Dissolved minerals enter into plants at the same time as water.
  • The minerals are in the form of ions.
  • Ions are charged particles.
  • These ions are absorbed actively i.e. energy inside the roots is used to pull the ions.
  • This is because the ion in the soil are in lower concentrations which means they cannot be taken up via osmosis.
  • The ions that would otherwise enter the plant by diffusion would be insufficient to sustain the plant.
  • The ions are thus absorbed via active uptake against the diffusion gradient.
  • The minerals and water enter the plants via the roots and move up to all parts of the plant.

To access more topics go to the Integrated Science Notes page.

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By | 2017-01-17T11:16:11+00:00 January 24th, 2016|Notes, O Level Science Notes, Ordinary Level Notes|0 Comments

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He holds an Honours in Accountancy degree from the University of Zimbabwe. He is passionate about technology and its practical application in today's world.

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