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What happens when pressure greater than atmospheric pressure is applied to pure water or solution ?

Water potential is increased when pressure greater than the atmospheric pressure is applied to pure water. 
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How is mycorrhizal association helpful in absorption of water and minerals in plants?


Mycorrhiza : It is the symbiotic association between roots of some plants and fungi. The hyphae provide a very large surface area and absorb mineral ions and water from soil. This is not possible for roots. The fungi provides mineral and water to roots. The hyphae secrete chemicals which protect the roots from pathogens. Thus  mycorrhizal association is helpful in absorption of water and minerals in plant cells. 

 

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Difference between Diffusion and Osmosis

Diffusion

Osmosis

1.It is the process of movement of the molecules from high concentration to low concentration until molecules get uniformly distributed.

1.It is the process of diffusion of only solvent of water molecules from its higher concentration to lower concentration via semi permeable membrane.

2. Semi permeable membrane is not needed.

2. Semi permeable membrane is essential. 

3. It involves the movement of both solute and solvent

3. Osmosis involves movement of solvent molecules only.

 

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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. 

 

 

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What essential role does the root endodermis play during mineral absorption in plants?

The endodermal cells have transport proteins which act as control points, to adjust the quantity and types of solutes that reach the xylem. The suberin layer of the endodermis allows unidirectional active transport of the ions and the symplastic movement of water. 

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