NEET Previous Year Questions (2016-2024): Transport in Plants (Old NCERT) PDF Download

Q.1.  Given below are two statements :       (NEET 2023)
Statement I : The forces generated transpiration can lift a xylem-sized column of water over 130 meters height.
Statement II : Transpiration cools leaf surfaces sometimes 10 to 15 degrees evaporative cooling.

In the light of the above statements, choose the most appropriate answer from the options given below :
(a) Both Statement I and Statement II are correct
(b) Both Statement I and Statement II are incorrect
(c) Statement I is correct but Statement II is incorrect
(d) Statement I is incorrect but Statement II is correct

Ans. (a)

Statement I is correct as measurements reveal that the forces generated by transpiration can create pressures sufficient to lift a xylem sized column of water up to 130 meters high.
Statement II is also correct as transpiration cools leaf surfaces, sometimes 10 to 15 degrees, by evaporative cooling.

Q.2.  Movement and accumulation of ions across a membrane against their concentration gradient can be explained by      (NEET 2023)
(a) Osmosis
(b) Facilitated Diffusion
(c) Passive Transport
(d) Active Transport

Ans. d

Movement and accumulation of ions across a membrane against their concentration gradient can be explained by active transport. It uses energy to transport molecules from lower concentration to a higher concentration. 

Q.3.  Match List I with List II :       (NEET 2023)

Choose the correct answer from the options given below :
(a) A – II, B – IV, C – I, D – III
(b) A – IV, B – III, C – II, D – I
(c) A – III, B – I, C – IV, D – II
(d) A – II, B – I, C – IV, D – III

Ans. a

Cohesion represents mutual attraction between water molecules. Adhesion represents attraction of water molecules to polar surfaces Surface tension represents water molecules are attracted to each other in the liquid phase more than to water in the gas phase. Guttation represent loss of water in liquid phase.

Thus, option (1) is correct.

Q.4. Which of the following is not observed during the apoplastic pathway?     (NEET 2022)
(a) The movement does not involve crossing of cell membrane
(b) The movement is aided by cytoplasmic streaming
(c) Apoplast is continuous and does not provide any barrier to water movement
(d) Movement of water occurs through intercellular spaces and walls of the cells

Ans. b

During the apoplastic movement the movement is not aided by cytoplasmic streaming. In Symplastic pathway the movement is aided by the cytoplasmic streaming.

• Inside a plant, the apoplast is the space outside the plasma membrane within which material can diffuse freely. It is interrupted by the Casparian strip in roots, by air spaces between plant cells and by the plant cuticle.
• The apoplastic pathway involves the movement of water through the intercellular spaces and the cell walls.
• This movement does not involve crossing the cell membrane.
• Water movement through the apoplast is dependent on the gradient.
• The apoplast does not provide any barrier to water movement, and water moves through mass flow.
• When water evaporates into the intercellular spaces or the atmosphere, tension develops in the continuous stream of water in the apoplast.
• Mass flow of water occurs due to the adhesive and cohesive properties of water.

Q.5. "Girdling Experiment" was performed by Plant Physiologists to identify the plant tissue through which:     (NEET 2022)
(a) Food is transported
(b) For both water and food transportation
(c) Osmosis is observed
(d) Water is transported

Ans. a
"Girdling Experiment" was performed by Plant Physiologists to identify the plant tissue through which food is transported. On the trunk of a tree a ring of bark up to a depth of the phloem layer, can be carefully removed. In the absence of downward movement of food the portion of the bark above the ring on the stem becomes swollen after a few weeks. This simple experiment shows that phloem is the tissue responsible for translocation of food and that transport takes place in one direction, i.e., towards the roots.

Q.6. Addition of more solutes in a given solution will:     (NEET 2022)
(a) lower its water potential
(b) make its water potential zero
(c) not affect the water potential at all
(d) raise its water potential

Ans. a

Water potential is the measure of the potential energy of water molecules in a solution, and it determines the direction of movement of water molecules. When solutes are added to a solution, they bind with water molecules and decrease the number of free water molecules available. This decrease in free water molecules leads to a decrease in the water potential of the solution.

Thus, the addition of more solutes in a given solution will lower its water potential.

Q.7. Match List - I with List-II.     (NEET 2021)

Choose the correct answer from the options given below.

      (a) (b)  (c) (d)

(a) (iii) (i)  (iv) (ii)
(b) (ii)  (i)  (iv) (iii)
(c) (ii) (iv)  (i)  (iii)
(d) (iv) (iii) (ii)  (i)

Ans. c

• Guttation - Water loss in its liquid phase is known as guttation.
• Cohesion – mutual attraction between water molecules.
• Adhesion – attraction of water molecules to polar surfaces (such as the surface of tracheary elements).
• Surface Tension – water molecules are attracted to each other in the liquid phase more than to water in the gas phase.

Q.8. The process responsible for facilitating loss of water in liquid form from the tip of grass blades at night and in early morning is:     (NEET 2020)
(a) Imbibition
(b) Plasmolysis
(c) Transpiration
(d) Root Pressure

Ans. d

• Root pressure is the process responsible for facilitating loss of water in liquid form from the tip of grass blades at night and in early morning.
• Root pressure is a positive pressure that occurs inside the xylem when various ions from the soil are transported into the roots' vascular tissues.
• This pressure can push water up to small heights in the stem.
• Excess water collects in the form of droplets around special openings of veins near the tip of grass blades and leaves of many herbaceous parts.
• Such water loss in its liquid phase is known as guttation.
• This is observable at night and early morning when evaporation is low.
• The greatest contribution of root pressure may be to re-establish the continuous chains of water molecules in the xylem, which often break under the enormous tensions created by transpiration.

Root Pressure

• Imbibition is the adsorption leading to absorption of water by hydrophillic substances. 
• Plasmolysis is the shrinking of the cell membrane and cytoplasm when a cell is undergoing exosmosis. 
• The loss of water in the form of water vapor from the aerial parts of the plant is called transpiration.

Q.9. Xylem translocates     (NEET 2019)
(a) Water, mineral salts, some organic nitrogen and hormones
(b) Water only
(c) Water and mineral salts only
(d) Water, mineral salts and some organic nitrogen only

Ans. a

Xylem is a type of transport tissue which is present in vascular plants. The basic function of xylem is transportation. Xylem  majorly transports water from roots to the parts of plants. Some times it also transports nutrients like mineral salts needed by the plant. It also translocates organic nitrogen and some hormones.

Q.10. What is the direction of movement of sugars in phloem?     (NEET 2019)
(a) Bi-directional
(b) Non-multi directional
(c) Upward
(d) Downward

Ans. a

The direction of movement of sugars in Phloem is Bi-directional.

• The vascular tissue called phloem in plants carries food, particularly sucrose, from one part of the plant to another, which is known as a source to a sink.
• Usually, the source is the part of the plant that produces food through photosynthesis, which is the leaf, while the sink is the part that needs or stores the food. However, the source and sink can be reversed, depending on the season or the plant's needs.
• During the growing season, the movement of sugars is usually from the leaves to the roots as the plant needs more energy for growth and development, which is a downward direction.
• Sugar stored in roots may be mobilised to become a source of food in the early spring when the buds of trees act as a sink, requiring energy for growth and development of the photosynthetic apparatus.
• Since the relationship between the source and sink is variable, the direction of movement in the phloem can be either upwards or downwards, which is bi-directional.

Q.11. Which of the following is not a feature of active transport of solutes in plants?     (NEET 2019)
(a) Occurs against concentration gradient
(b) Non-selective
(c) Occurs through membranes
(d) Requires ATP

Ans. b

Active transport is a type of transport in plants where solutes are transported from an area of lower concentration to an area of higher concentration, i.e., against the concentration gradient. This process requires energy in the form of ATP, which is generated through cellular respiration.

The features of active transport of solutes in plants are:

(a) Occurs against concentration gradient: Active transport occurs against the concentration gradient, i.e., from an area of low concentration to an area of high concentration.

(b) Selective: Active transport is a selective process, which means that it only transports specific solutes.

(c) Occurs through membranes: Active transport occurs through the cell membrane or organelle membranes.

(d) Requires ATP: Active transport requires energy in the form of ATP to transport solutes.

Q.12. What will be the direction of flow of water when a plant cell is placed in a hypotonic solution?     (NEET 2019)
(a) Water will flow in both directions
(b) Water will flow out of the cell
(c) Water will flow into the cell
(d) No flow of water in any direction

Ans. c

• When a plant cell is placed in a hypotonic solution, the direction of flow of water will be into the cell.
• A hypotonic solution is a solution with a lower solute concentration compared to the inside of the cell. Therefore, water will move from an area of high concentration, which is outside the cell, to an area of low concentration, which is inside the cell.
• As a result, the cell will swell up and become turgid due to the inflow of water, which is important for maintaining the shape and structure of the plant. If the influx of water continues, the cell may even burst due to the excess water.

Q.13. Stomatal movement is not affected by     (NEET 2018)
(a) Temperature
(b) Light
(c) O₂ concentration
(d) CO₂ concentration

Ans. c

• Stomatal movement refers to the opening and closing of stomata, which is regulated by various internal and external factors.
• The external factors that affect stomatal movement include temperature, light, humidity, and the concentration of carbon dioxide (CO₂). Of these, temperature and light are two significant factors that have a direct impact on stomatal opening and closing.
• However, the concentration of oxygen (O₂) does not play a direct role in regulating stomatal movement. Although oxygen is exchanged through the stomata, its concentration in the surrounding atmosphere does not significantly affect the opening and closing of stomata.

Q.14. The water potential of pure water is     (NEET 2017)
(a) Less than zero
(b) More than zero but less than one
(c) More than one
(d) Zero

Ans. d

• Water potential is the measure of the potential energy of water in a system. It determines the direction and rate of water movement across membranes and tissues. The water potential of pure water is a reference point, and it is defined as zero.
• Pure water has the highest possible concentration of water molecules, with no solutes present to lower the concentration or restrict water movement. Therefore, the water potential of pure water is zero, and all other solutions will have a negative water potential relative to it.

Q.15. Which of the following facilitates opening 0f stomatal aperture?     (NEET 2017)
(a) Decrease in turgidity of guard cells
(b) Radial orientation of cellulose microfibrils in the cell wall of guard cells
(c) Longitudinal orientation of Cellulose microfibrils in the cell wall of guard cells
(d) Contraction of outer wall of guard cells

Ans. b
When turgidity increases within the two guard cells flanking each stomatal aperture or pore, the thin outer wall bulge out and force the inner walls into a crescent shape. This results in the opening of stomata. The opening of stomata is also aided by the radial orientation of cellulose microfibrils in the cell wall of guard cells rather than longitudinal orientation.

Q.16. A few drops of sap were collected by cutting across a plant stem by a suitable method. The sap was tested chemically. Which one of a following test results indicates that it is phloem sap?     (NEET 2016)
(a) Acidic
(b) Alkaline
(c) Low refractive index
(d) Absence of sugar

Ans. b
Phloem sap is generally alkaline with pH ranging from 7.3 - 8.5 and contains high levels of  K⁺ and Mg²⁺. Hence, the chemical test for alkalinity will help to identify that the exudated sap is phloem sap. So, the correct answer is 'Alkaline'.

Q.17. Water vapour comes out from the plant leaf through the stomatal opening. Through the same stomatal opening carbon dioxide diffuses into the plant during photosynthesis. Reason out the above statements using one of following options.     (NEET 2016)
(a) Both processes cannot happen simultaneously.
(b) Both processes can happen together because the diffusion coefficient of water and CO₂ is different.
(c) The above processes happen only during night time.
(d) One process occurs during day time, and the other at night.

Ans. b
In actively growing plants, water is continuously evaporating from the surface of leaf cells through stomatal opening exposed to air. This is called transpiration. Through the same stomatal opening carbon dioxide diffuses into the plant during photosynthesis. Simultaneously as both are the process of simple diffusion occurs in order of diffusion pressure gradient or diffusion coefficient.

Q.18. Transpiration and root pressure cause water to rise in plants by:     (NEET 2015) 
(a) Pulling and pushing it, respectively
(b) Pushing it upward
(c) Pushing and pulling it, respectively
(d) Pushing it upward

Ans. a

• Transpiration is the process by which water is lost from the leaves through small pores called stomata. As water is lost, it creates a negative pressure, or tension, that pulls more water up from the roots. This pulling force is known as the transpiration pull and is responsible for most of the water movement in plants.
• Root pressure, on the other hand, is the upward pressure exerted by the roots as they absorb water from the soil. This pressure helps to push water up the stem and can supplement the transpiration pull.

Q.19. A column of water within xylem vessels of tall trees does not break under its weight because of:     (NEET 2015) 
(a) Tensile strength of water
(b) Lignification of xylem vessels
(c) Positive root pressure
(d) Dissolved sugars in water

Ans. a
Due to tensile strength of water, a column of water within xylem vessels of tall trees does not break  under its weight.

This strength helps in resisting the pulling force and it depends on water properties like surface tension, cohesion and adhesion.

Q.20. Root pressure develops due to:     (NEET 2015) 
(a) Low osmotic potential in soil
(b) Passive absorption
(c) Increase in transpiration
(d) Active absorption

Ans. d
Active absorption creates root pressure. In this process, the expenditure of energy takes place for the movement of substances against concentration gradient.

Q.21. Roots play insignificant role in absorption of water in:     (NEET 2015) 
(a) Pistia
(b) Pea
(c) Wheat
(d) Sunflower

Ans. a
Pistia a hydrophyte plant where absorption of water by root is not important.