Tag: osmosis in plants

Questions Related to osmosis in plants

A cell with DPD=5 is surrounded by A,B,C and D cell having OP and Tp respectively 5 and 4, 7 and 5, 3 and 2, 0.5 and 0. From which cell it will withdraw water fast? 

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. D

  2. C

  3. B

  4. A

Show answer
Correct Option: D
Explanation:

DPD is the difference between Osmotic pressure and Turgor pressure. 

For cell A the DPD is 1.
For cell B the DPD is 2.
For cell C the DPD is 1
For cell D the DPD is 0.
So, the correct answer is 'D'.

Which of the following is correct about DPD?

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. DPD is the reduction in diffusion pressure of solvent in a system over its pure state

  2. DPD = OP - TP

  3. DPD is zero, entry of water will stop

  4. All of the above

Show answer
Correct Option: D
Explanation:

DPD is diffusion pressure deficit. It is the reduction in the diffusion pressure of solvent in a system over its pure state due to presence of solutes in it and forces opposing diffusion. Pure solvent has the maximum diffusion pressure. DPD is the difference between the osmotic pressure (OP) and turgor pressure (TP). When a cell is turgid, its OP is equal to TP and DPD is zero. When DPD is zero, the entry of water will stop as turgid cell cannot absorb any more water.

Thus, the correct answer is 'All of the above.'

Which of the following is not correct about DPD?

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. It is the loss of diffusion pressure

  2. Maximum value of DPD is equal to OP

  3. DPD of pure water is zero

  4. Low DPD means small gap between the value of OP and TP

Show answer
Correct Option: A
Explanation:

DPD or diffusion pressure deficit is the difference between the diffusion pressure of a solution and a pure solvent when both are subjected to the same atmospheric pressure. Since pure water does not contain any solute particles, therefore it has zero DPD. Movement of water is always from low DPD to high DPD. When increasing turgor pressure becomes equal to decreasing osmotic pressure, the entry of water into the cell would stop.

In a flaccid condition, the value of DPD equals OP.
Hence, the correct answer is 'It is the loss of diffusion pressure'.

Which option is true for a fully turgid cell?

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. OP $=$ DPD

  2. OP $=$ zero

  3. DPD $=$ Zero

  4. TP $=$ Zero

Show answer
Correct Option: C
Explanation:

As the cell becomes fully turgid, the value of turgor pressure becomes equal to that of solute potential $(\Psi _s)$ so that water potential $(\Psi _w)$ or DPD becomes either zero or equal to that of external hypotonic solution.
$\Psi _w=\Psi _s+\Psi _p=0$

Though there is no net movement of water between the cell and its environment, equilibrium is dynamic and not static. Equal exchange of water molecules continues between the cell and its environment.
So, the correct answer is 'DPD = Zero'.

Which of the following equations is correct in respect of osmotic phenomenon ?

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. DPD = OP - TP

  2. DPD = OP + TP

  3. DPD = OP $\times$ TP

  4. DPD = OP $\div$ TP

Show answer
Correct Option: A
Explanation:

DPD = Diffusion pressure deficit

OP = Osmotic pressure
TP = Turgor pressure
Diffusion pressure of a pure solvent is more than the solution and this difference is given by DPD.
TP is developed when water starts entering the cell and the osmotic pressure is the maximum pressure a system can develop in comparison to pure water.
Hence DPD is given when we subtract the TP from the OP.
So the correct answer is 'DPD = OP - TP'.

If DPD represents diffusion pressure deficit, OP is the osmotic pressure and TP is the turgor pressure, then which of the following equations is correct?

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. DPD $=$ OP $=$ TP

  2. DPD $=$ OP $+$ TP

  3. DPD $=$ OP $-$ TP

  4. DPD $=$ OP

Show answer
Correct Option: C
Explanation:

The reduction in the diffusion pressure of water in a solution over its pure state is called diffusion pressure deficit or DPD. Diffusion pressure deficit is also called suction pressure. It value is equal to the osmotic pressure or potential (OP) (positive value taken in bars or atm) of the solution in a cell or system minus the wall pressure (WP) ($=$ turgor pressure, TP) which opposes the entry of water into it provided the external water is pure DPD $=$ OP $-$ WP ($=$TP)

Water is absorbed by a system having higher DPD from another system with lower DPD.
So, the correct answer is 'DPD $=$ OP $-$ TP'.

Water moves from a cell with __________ DPD to a cell with ________ DPD.

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. Higher, Lower

  2. Lower, higher

  3. Lower, lower

  4. Higher, higher

Show answer
Correct Option: B
Explanation:

DPD (diffusion pressure deficit) opposes the diffusion process. so from that we conclude that water moves from a cell with lower DPD to a cell with higher DPD.
Correct option is B.

When a plasmolysed cell is placed in a hypotonic solution then water will move inside the cell this will happen due to which force?

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. Diffusion Pressure Deficit

  2. Osmotic Pressure

  3. Wall Pressure

  4. None of the above

Show answer
Correct Option: A
Explanation:
When a plant cell is placed in hypotonic solution, water enters into a cell by osmosis and as a result turger pressure develops. The cell membrane get stretched and osmotic pressure of cell decreases. As cell absorbs more and more water its Total Pressure increases and Osmotic Pressure decreases. When a cell is fully turgid, its OP is equal to TP and DPD is zero. Turgid cells cannot absorb any more water. Thus, with reference to plant cell, the DPD can be described as actual thirst of cell for water and can be expressed as DPD=OP-TP.

When DPD is zero, entry of water will stop. Thus it is DPD that tends to equate and represents water absorbing ability of a cell, it is also called suction force (SF) or suction pressure (SP).
The term diffusion pressure deficit (DPD) was coined by B.S Meyer in 1938. Originally DPD was described as suction pressure by Renner (1915). It is reduction in the diffusion pressure of water in solution or cell over its pure state due to presence of solutes in it and forces opposing diffusion.
DPD of a solution is equal to its osmotic pressure i.e. DPD = OP(of solution). DPD of a cell is influence by both osmotic pressure and wall pressure (turgor pressure) which opposes the endosmotic entry of water, i.e. DPD = OP - Wall pressure. DPD is directly proportional to the concentration of the solution. DPD decreases with dilution of solution. The actual pressure with which cell absorbs water is called "suction pressure".

Osmotic Potential - The potential of water molecules to move from a hypotonic solution (more water, less solutes) to a hypertonic solution (less water, more solutes) across a semi permeable membrane.
Water potential (Symbol Ψ). The difference between the chemical potential of the water in a biological system and the chemical potential of pure water at the same temperature and pressure. It is manifested as a force acting on water molecules in a solution separated from pure water by a membrane that is permeable to water molecules only and can be expressed as the sum of the solute potential and the pressure potential: Ψ = Ψs + Ψp 

A and B are contiguous cells. A has osmotic pressure (OP) = 10 atm. Turgor pressure (TP) = 7 atm and Diffusion pressure deficit (DPD) = 3atm. B has OP = 8 atm, TP = 3 atm, DPD = 5 atm. The direction taken by the water would be

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. No movement of water

  2. Equilibrium between the two

  3. Movement of water from A to B

  4. Movement of water from B to A

Show answer
Correct Option: C
Explanation:

Movement of water from A to B since water flows in the direction from low DPD to high DPD.  'A' cell has lower DPD than 'B' so the movement of water from A cell to B cell will be the correct answer.

In a plant cell DPD is zero when it is 

botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

  1. Plasmolysed

  2. Turgid

  3. Flaccid

  4. Incipient

Show answer
Correct Option: B
Explanation:

A cell is fully turgid means it is full of water i.e, it cannot absorb any more water. In a fully turgid cell DPD (Diffusion Pressure Deficit) is zero and the net movement of water into the cell stops satisfying the equation  DPD =  OP +  TP. Therefore, for the fully turgid cells has DPD is zero satisfying osmotic pressure (OP) and turgor pressure (TP) must be equal, when a cell absorbs more and more water turgor pressure increases thereby it will be positive value and osmotic pressure decreases hence it is negative value.

So, the correct answer is option B.