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Differentiate between apoplast pathway and symplast pathway.

Apoplast pathway

Symplast pathway

1. Apoplast is the system of adjacent walls and continuous through the plant except at casparian strips.

2. There is no role of plasmodesmata.

3. It occurs through cell wall and intercellular spaces. Cell membrane is not crossed.

4. It is fast.

5. It is not aided by streaming movement of cytoplasm.

6. It does not involve osmosis.

1. It is the system of interconnected protoplasts.

2. Continuity of protoplasm from one cell to another cell is through plasmodesmata.

3. It occurs through cell membrane.

4. It is slow.

5. It is aided by streaming movements of cytoplasm.

6. It involves osmosis.

 
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Explain why pure water has maximum water potential.

The greater the concentration of water in a system, the greater its water potential. In pure form water has maximum concentration as no substance is dissolved in it, thus it has the maximum water potential. 
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What role does root pressure play in water movements in plants?

Root pressure only provides a moderate push in the overall movement of water or water transport. It does not play a major role in the movement of water up the tall trees. 
The main contribution of the root pressure is to re-establish the continuous flow of water molecules in the xylem which often break under the enormous tensions created by transpiration.


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Distinguish between imbibition and diffusion.

Imbibition

Diffusion

1. It is the proces by which solid absorbs water and swells up without getting dissolved.

2. In this only water or liquid is absorbed.

3. Imbibant is required.

4. Due to imbibition pressure is increased.

 

1. It is the diffusion of molecules from higher concentration to lower concentration.

2. This may occur in water, liquids, solids and gases.

3. Imbibant is not required .

4. The pressure is reduced after diffusion.

 

 
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What are porins ? What role do they play in diffusion ?


Porins : These are special proteins having large pores and are present in outer membrane of plastids, mitochondria and some bacteria. These allow molecules to pass even upto size of small proteins Thus moelcules can diffuse through them. They help in facillitated diffusion. 
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