in ch - tissue in the process of phloem and xylem how the water goes up from roots to plants,as their is gravitation too,so how??

Asked by seemakumar494 | 12th Feb, 2019, 11:45: PM

Expert Answer:

Water moves upwards from the roots to the different plant parts mainly by two processes-

  • Root pressure
  • Transpirational pull

Root Pressure

  • Water enters the root hair through osmosis, and mineral ions enter the root cells by active transport.
  • Both water and minerals move upward from cell to cell through the cortex of the root by osmosis.
  • From the cortex, water and minerals are brought to the xylem.
  • The sap which contains water and dissolved minerals move upwards from the root cells through the xylem. The upward movement of sap is called the ascent of sap.
  • The xylem vessels of the roots are in continuation with the xylem vessels of the stem.

Transpiration Pull

  • Transpiration is the loss of water in the form of water vapour from the aerial parts of a plant.
  • It occurs through openings called stomata.
  • Water loss through evaporation lowers the concentration of water inside the mesophyll cells.
  • Due to this, water enters mesophyll cells from neighbouring xylem vessels through osmosis.
  • As water evaporates from the leaves, a suction force is created. This force helps to draw more water up through the stem which causes the roots to absorb more water from the soil.
  • Higher the rate of transpiration, greater the rate of absorption of water and solutes from the soil.
  • Transpiration also helps in maintaining the temperature of the plant body.

Answered by Sheetal Kolte | 13th Feb, 2019, 11:54: AM