NCERT Solutions for Class 11 Biology Chapter 11
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Transport in Plants: Solutions
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Important Notes on Transport in Plants
- Osmotic Pressure-External pressure applied to prevent the diffusion of water. It depends upon solute concentration. Numerically, osmotic pressure is equal to osmotic potential osmotic pressure has positive (+) sign. Osmotic potential has negative (-) sign.
- Turgor Pressure-Due to osmotic entry of water, the protoplasm of a plant cell presses the cell wall towards the outside with a force, it is called Turgor Pressure.
- Diffusion Pressure-The pressure exerted by the tendency of the particles to diffuse from the area of higher concentration to lower concentration. It is directly proportional to the concentration of particles of diffusing substance.
- Osmosis is movement of solvent or water molecules from the region of their higher diffusion pressure or free energy to the region of their lower diffusion pressure of free energy across a semipermeable membrane. Water molecules move from higher water potential to lower water potential until equilibrium is reached.
- Hypotonic solution: The external solution which is more dilute than the cytoplasm.
- Hypertonic solution: The external solution, which is more concentrated than the cytoplasm.
- Isotonic solution: When the external solution balances the osmotic pressure of the cytoplasm.
More to Know
- Plasmolysis: Process of shrinkage of protoplast in a cell due to exosmosis in hypertonic solution. If a plasmolysed cell is placed in water or a hypotonic solution it becomes turgid.
- Casparian strip: It is the tangential as well as radial walls of endodermal cells having the deposition of water impermeable suberin.
- Transport of water in plants: Water is absorbed by root hairs by diffusion. Then water moves upto xylem by two pathways apoplast and symplast pathway.
Apoplast Pathway-Movement occurs through the intercellular spaces or walls of the cell, without entering the cytoplasm. This movement is fast. In roots, movement of water occurs via apoplast except at the carparian strip, most of water enters through apoplast.
Water enters the cell through cell membrane and travels intercellularly through plasmodesmata. This movement is slow. At casparian strip region water moves through symplast.
Imbibition: Imbibition is the phenomenon of absorption of water by the solid particles of an adsorbent causing it to enormously increase in volume without forming a solution.