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The following points highlight the four experiments on the conduction of water in plants.
Experiment # I:
Immerse a Peperomia plant and a few stalks of tuberose (Rajanigandha) in water coloured with eosin or acid fuchsin.
After some time observe narrow streaks of pink in the transparent stem and pink veins of Peperomia leaves showing the movement of coloured water through inner conducting xylem strands.
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In tuberose the white flowers take a beautiful pink shade after about 24 hours, again showing upward movement of coloured solution through the stalks to the flowers themselves. The colouring of the white flowers involves also lateral diffusion of the dye.
Experiment # II:
Immerse leafy twigs of Vinca, Trabernaemontana coronaria (Tagar), etc., in red- coloured solutions. After some time the detection of the coloured soln. at various heights of the stem can be made by visual observation and also by making sections and looking through a microscope.
It becomes at once evident that the red colourings are primarily confined to the xylem vessels, proving again that the xylem strands are the main path of the upward movement of the solutes in plants.
Experiment # III:
Ringing Experiment: Take a forked twig of Vinca or any other suitable plant and leave its main axis intact. From the left-hand fork remove all the cortical portions from a narrow zone. Sever the central woody strand very carefully from the right-hand fork leaving the cortical tissue undamaged. (See Fig. 686.) Immerse (he lower end of the main axis in water coloured with eosin in a beaker.
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Observe after a few hours. It is seen that leaves of the right-hand fork have considerably wilted and no eosin could be detected above the incision, proving that severance of vascular strands stops upward translocation of liquids, causing the leaves to wilt.
For the same reason, the leaves of the left-hand fork are more or less unaffected and eosin can be easily detected above the stripped zone—removal of cortical tissue does not seriously interfere with water conduction if the xylem remains intact.
Experiment # IV:
Two leafy Vinca or Tagar twigs are taken, the lower end of one is dipped in boiling water for some time in one case and in a strong solution of CuSO4 or any other toxic substance in the other. After such drastic treatment which kills all the living cells in the treated regions, the twigs are put in a beaker containing eosin-coloured water. After about 24 hours, eosin can be detected in the xylem strands throughout the stem and leaf of both the twigs (there is very little wilting of the leaves) indicating that living cells take a very small part, if any, in the upward conduction of liquid through the plant.
