Transport of Water Experiment


 
 
Concept Explanation
 

Transport of Water Experiment

Some experiments on absorption and conduction of water in the plants

Experiment 1 :- To show that roots absorb water

  • Take a test tube(A) filled with water.
  • Pull out a young leafy plant from the soil with its roots intact.
  • Insert the roots into the test tube soon.
  • Put a few drops of oil in the test tube to prevent any loss of water by evaporation.
  • Mark the level of water.
  • Set up a similar test tube (B) but without the plant.
  • In a day or two you will find that the level of water in the test tube(A) falls but not in the test tube(B), proving that water lost in test tube A was absorbed by the roots.
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    Experiment 2 :- To show that water is conducted upwards through the xylem.

  • A medium - sized young balsam plant is uprooted, washed and placed in a beaker containing a stain eosin solution(pink) in water.
  • The roots should be completely submerged in the solution.
  • This set up  is kept aside for 3 - 4 hours.
  • At the end of this period, the plant is taken out of the solution and washed in tap water.
  • Then, a transverse section of the roots, stem and leaves is made and examined under a microscope.
  • The xylem vessels will appear distinct from the rest, because these will be stained red by the dye.
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    Experiment 3 :-

  • Conduction of water through xylem can  also be shown by another but delicate experiment.
  • Take two leafy shoots such as those of a balsam plant, which have been cut under water to prevent any air bubbles getting in .
  • Keep their lower ends dipping in water. Remove about 3 cm long, outer ring of the stem in one of them as shown in beaker(A), keeping the central part intact(ringing experiment also called girdling).
  • In the other beaker (B), remove an equal length of the central part (xylem) after incising the stem for full thickness and keeping the peripheral part intact.
  • The shoots are then fixed to stands are allowed to remain  for about two days with their lower ends immersed in water.
  • It will be found that the leaves in the first twig remain  turgid and stand out almost normally, but those in the second twig get wilted and droop down.
  • The experiment proves that water is conducted upwards in a plant through the deeper part i.e. xylem.
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    Experiment 4 : To show that food from the leaves is conducted downwards through the phloem in the stem.

  •  Cut a ring round the stem of a healthy potted plant or around a thin twig of guava or any other tree, deep enough to penetrate the phloem and cambium but not the xylem(Girdling) .
  • It will be seen that sap starts oozing out from the farther cut margin  of the stem showing thereby that sap in the peripheral parts flows in a downward direction.
  • After some weeks, it will be observed that the part of the stem  above the ring has grown in diameter, and the stem below the girdle has stopped growing and may even die when the stored organic contents of the lower part are exhausted.
  • The fresh healthy condition of the leaves, in this experiment, also proves that the leaves continue to get a supply of water through the deeper located xylem.
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