Explain The Concept Of Path Of Water ?

1.	Explain The Concept Of Path Of Water ?
Answer» It is well established that longitudinal water MOVEMENT through the plant takes place predominantly through the xylem, but the whole cross-sectional area of the root or stem may be available for flow, except in dense woody regions. Evidence for the xylem path comes from the observation that water flow is not immediately stopped when a ring of TISSUES external to the xylem is removed. If a section of xylem is removed leaving other tissues intact, ascent of sap is impaired. When solutions labeled with water-soluble dyes, radioactive solutes or water containing 3H or 18O are supplied to plants, the label is rapidly detected in the xylem of roots and stems, particularly in the vessels and tracheid’s. If the cut END of a flowering twig of tuberose is dipped in eosin solution its flowers turn red. The t.s. of the stem shows only xylem vessels stained red. That the lumen of xylem vessels are the path through which water moves can be shown by clogging the vessels of a balsam twig by gelatin jelly or low melting point paraffin. The cut end of the twig is dipped in molten gelatin jelly or low melting paraffin. After a few minutes the gelatin or paraffin enters the xylem cavities and block them. A section is removed from the cut end to expose the vessel walls and xylem parenchyma, although the cavities are still blocked. Then the cut end is put in water. The leaves on the twig are found WILTING as water cannot go up through the wall of xylem elements sufficiently to maintain turgor pressure. This clearly indicates that water TRANSLOCATION takes place mainly through the xylem vessels.

Answer»

It is well established that longitudinal water MOVEMENT through the plant takes place predominantly through the xylem, but the whole cross-sectional area of the root or stem may be available for flow, except in dense woody regions. Evidence for the xylem path comes from the observation that water flow is not immediately stopped when a ring of TISSUES external to the xylem is removed.
If a section of xylem is removed leaving other tissues intact, ascent of sap is impaired. When solutions labeled with water-soluble dyes, radioactive solutes or water containing 3H or 18O are supplied to plants, the label is rapidly detected in the xylem of roots and stems, particularly in the vessels and tracheid’s.
If the cut END of a flowering twig of tuberose is dipped in eosin solution its flowers turn red. The t.s. of the stem shows only xylem vessels stained red. That the lumen of xylem vessels are the path through which water moves can be shown by clogging the vessels of a balsam twig by gelatin jelly or low melting point paraffin.
The cut end of the twig is dipped in molten gelatin jelly or low melting paraffin. After a few minutes the gelatin or paraffin enters the xylem cavities and block them. A section is removed from the cut end to expose the vessel walls and xylem parenchyma, although the cavities are still blocked. Then the cut end is put in water.
The leaves on the twig are found WILTING as water cannot go up through the wall of xylem elements sufficiently to maintain turgor pressure. This clearly indicates that water TRANSLOCATION takes place mainly through the xylem vessels.

Explain The Concept Of Path Of Water ?

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