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NEET NEET Questions — Free MCQ Practice

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To initiate cell plasmolysis, the salt solution should be :

A.

Isotonic

B.

Hypertonic

C.

Hypotonic

D.

None of the above.

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Explanation

(A) An isotonic solution is a solution where there is no net movement of molecules due to equal concentration on both sides of the cell.

(B) Hypotonic solution is a solution where the movement of molecules is from outside to the inside of the cell.

(C) A hypertonic solution is a solution where the movement of molecules is from inside to outside of the cell.

A hypertonic solution is a solution which contains a high concentration of salt.

When the salt solution is the hypertonic solution then water will enter from outer soil inside the cell so that water will be available for photosynthesis.

So, the correct answer is 'Hypertonic'.

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Plant cells submerges in distilled water will become:

A.

Turgid

B.

Flaccid

C.

Plasmolysed

D.

Impermeable.

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Explanation

Plant cells have plasma membrane and rigid cellulose cell wall.

When the cell is placed or immersed in distilled water, the water is absorbed by osmosis.

The cell becomes turgid .

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Water potential in the leaf tissue is positive (+ve) during:

A.

Excessive transpiration

B.

Low absorption

C.

Low transpiration

D.

High Transpiration

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Explanation

Water potential depends on the number of water molecules in the system. More the number of water molecules, greater will be the water potential. Water potential of all solutions is negative in comparison to pure water which has water potential as zero. Under the conditions, when there are more water molecules in the system, water potential is expected to be higher, e.g., under conditions of low transpiration in leaf tissue the water potential is expected to be positive. When transpiration is low, considerably more water molecules will be stuffed up inside leaf in the intercellular spaces giving rise to a positive water potential.

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If cohesion-tension transpiration theory is correct then a break in water column in xylem vessels :

A.

should cause the mesophyll cells to become flaccid and result in wilting of leaves.

B.

should increase the water contents of leaves

C.

shouls have no effect at all

D.

should increase the rate of photosynthesis.

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Explanation

During the ascent of sap, the continuous water column is required. This is provided by the cohesive and adhesive forces between the water molecules. Due to the cohesive forces between the water molecules, the water column does not break. However, a break in the water column will result in the hindrance in the ascent of sap. This causes the wilting of leaves due to the inadequate water supply. There will be a loss of turgidity of leaves. This will result in the drooping, rolling and folding of leaves.
Thus, the correct answer is option C.

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The phytohormone which is supposed to be one of the factor responsible for regulating the opening and closing of stomata:

A.

ABA

B.

GA

C.

IBA

D.

Kinetin

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Explanation

Abscisic acid promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy]. It also promotes closing of stomata.

● ● ● ● ●

Which ion accumulate in the guard cells at the time of opening of stomata :

A.

P

B.

K

C.

Mg

D.

Ca

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● ● ● ● ●

Dry wooden stakes if driven into a small crack in a rock and then soacked, can develop enough pressure to split the rock. Such a pressure is built up through the phenomenon of :

A.

Imbition

B.

Butteress roots

C.

Prop roots

D.

Turgor pressure

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● ● ● ● ●

The cohesive force existing between molecules of water is contributing to :

A.

ascent of sap

B.

translocation

C.

plasmolysis

D.

osmosis.

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● ● ● ● ●

To initiate cell plasmolysis, the salt concentration must be :

A.

isotonic

B.

hypertonic

C.

hypotonic

D.

atonic

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● ● ● ● ●

The most accepted theory for stomatal opening and closing is :

A.

transpiration

B.

guard cell photosynthesis

C.

K⁺ efflux and influx

D.

starch glucose interconversion.

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NEET Practice Questions (MCQs) with Answers & Solutions

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