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Transport in Plants

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Briefly describe water potential. What are the factors affecting it ?

Water potential : This term was given by Slatyer and Taylor (1960). It is the difference in free energy or chemical potential per unit molal volume of water in a solution over its pure state at same temperature and pressure. It is denoted by Psi or Ψw and is expressed in Pascals (Pa). T

The water potential of pure water is always taken as zero at standard temperature and pressure.

Water potential (Ψw) is expressed as the sum of solute potential (Ψs) and pressure potential (Ψp).

Ψw = Ψs + Ψp

Factors affecting the water potential are as followwing:

i. Solute concentration - The dissolution of solute in water decreses its water potential. All mixtures have a water potential less than zero. More the solute more negative will be the water potential.

ii. Pressure - If pressure greater than the atmospheric pressure is aaplied to a pure water or solution, its water potential increases. 




What is transmembrane pathway ?

The movement of water through cell membranes is called trans membrane pathway.

Who introduced the apoplast—symplast concept ?

E. Munch (1930).

Give the term for the ability to resist a pulling force.

Tensile strength

Why the water is forced to move through cell membrane beyond endodermis ?

Water is forced to move through cell membranes beyond endodermis because of the suberin (waxy substance) present on radial walls of endodermal cells blocks water and solute movement through cell walls of endodermis. 

Why the cortex produces no resistance to movement of water ?

The cortical cells are loosely packed and produce no resistance to movement of water via cell walls or apoplast.