Biology

Plant Transport and Physiology

1,834 Questions

Access a comprehensive set of questions on plant transport mechanisms and physiological adaptations. Topics include water movement, translocation of food, and plant responses to external stimuli. These biology questions are essential for medical entrance exams and other science competitive tests.

Xylem and phloem transportTranspiration and evaporationPlant adaptationsGeotropic and phototropic responsesWater absorption by rootsRespiration in roots

Plant Transport and Physiology Questions

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

During absorption of water by roots, the water potential of cell sap is lower than that of

  1. Pure water and soil solution

  2. Neither pure water nor soil solution

  3. Pure water but higher than that of soil solution

  4. Soil solution but higher than that of pure water
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water flows from higher water potential to lower water potential. Water potential of pure water is zero. As solutes are dissolved in it, the water potential decreases. More the dissolved solutes, lower will be the water potential. Water potential of all the solutions is always negative. Hence, water flows from higher water potential (i.e., less negative water potential) towards a lower water potential (i.e., more negative water potential). It is clear that absorption of water will occur if water potential of cell sap is lower than pure water and soil solution.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Which of the following statement(s) is/are incorrect?

  1. Water and salts are taken simultaneously by root hairs.

  2. Plants absorb one thing at a time either water or inorganic salt.

  3. Plants absorb excess quantity of water.

  4. All of the above.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is wrong to believe that water absorption and absorption of mineral salts are two unrelated processes. In fact the active uptake of ions is partly responsible for the water potential gradient in roots, and therefore for the uptake of water by osmosis. Some ions also move into the epidermal cells passively. Since soil has less concentration of minerals; most of the minerals are absorbed actively.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Lignin and cellulose have affinity for water. This is called

  1. Adhesion

  2. Cohesion

  3. Root pressure

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • The attraction between the molecules of dissimilar substances is termed as adhesion. 
  • Walls of tracheid and vessels of xylem are made up of lignin and the cellulose. Hence due to the adhesive force, they have a close affinity for water.
  • So, the correct answer is option A.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Root hair absorbs water from soil through

  1. Turgor pressure

  2. Ion exchange

  3. Osmosis

  4. DPD
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Root hair absorbs water from soil through osmosis. Water will be absorbed by root hairs by osmosis as the environment in the soil is hypotonic. This kind of absorption takes place passively. The water can easily move from the region of higher concentration to the low concentration without expenditure of energy. The cell membrane of the root cells acts as a semipermeable membrane. It passes the epidermis, cortex, endodermis, casparian strip and pericycle and protoxylem and metaxylem.

So, the correct answer is option C.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Loss of water taken place through.

  1. Stomata, cell wall of mesophyll cells and hydathodes

  2. Stomata and cell wall of mesophyll cells

  3. Stomata and hydathodes

  4. Cell wall of mesophyll cells and hydiahodes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water loss in plants occurs through transpiration (stomata), cuticular transpiration, and guttation (hydathodes). The cell wall of mesophyll cells is the site where evaporation starts, making option A the most comprehensive.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Whose water potential is less than water potential of root hair during water absorption (by root hair)?

  1. Gravitational water

  2. Pure water

  3. Vacuolar sap

  4. Soil solution
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For water to move into the root hair via osmosis, the water potential inside the root hair (specifically the vacuolar sap) must be lower than that of the soil solution.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Rate of water absorption can be increased through 

  1. Decreased transpiration

  2. Decreased ion absorption

  3. Increased photosynthesis

  4. Increased transpiration
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The rate of transpiration is high on a bright sunny day. The water is lost from guard cell which leads to decrease in the water potential of guard cell as compared to the surrounding cell. To stabilize the water potential in the guard cell water rushes from the neighbouring cell which creates a cohesion pull in the xylem vessels to pull the water up to the guard cell. Thus, the rate of water absorption increases when the transpiration is high. 
So, the correct answer is option D.
Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Roots play insignificant role in absorption of water in

  1. Sunflower

  2. Pistia

  3. Pea

  4. Wheat
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pistia is a hydrophyte where absorption of water by root is insignificant   It floats on the surface of the water, its roots hanging submersed beneath floating leaves. 

So the correct option is "pistia".

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

The transpiration-driven ascent of xylem sap depends mainly upon _______ property of water.

  1. Cohesion

  2. Adhesion

  3. Surface tension

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There is a continuous column of water from root through the stem and into the leaves. The water column is present in tracheary elements. The column of water does not fall down under the impact of gravity because forces of transpiration provide both energy and necessary pull. Cohesion, adhesion and surface tension-keep the water in place.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Which of the following statements is incorrect?

  1. Endodermis is impervious to water due to the presence of suberized Casparian strips

  2. Xylem vessels and tracheids, being non-living, are parts of the apoplast

  3. Ascent of sap is best explained by root pressure theory

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cohesion tension theory(Cohesion-tension and transpiration pull theory) explains the ascent of sap best. It was put forward by Dixon and Jolly in 18941894. It was further improved by Dixon in 19141914. Therefore, the theory is also named after him as Dixon's theory of ascent of sap. Today most of the workers believe in this theory.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Choose the correct answers from the alternatives given.
Pressure on a plant cell wall caused by the osmotic movement of water is called

  1. Osmotic pressure

  2. Wall pressure

  3. Turgor pressure

  4. Tonic pressure
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When a plant cell is placed in the hypotonic solution, it causes endosmosis i.e. movement of surrounding water into the cell. This creates a turgor pressure against the rigid walls due to the entry of water.

Osmotic pressure is the hydrostatic pressure developed in a solution when it is separated from the pure solvent by a semi-permeable membrane in a rigid vessel.
Hence, the correct answer is 'Turgor pressure'.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Choose the correct answers from the alternatives given.
During the day most plants lose .......... and take up .......... 

  1. Carbon dioxide; oxygen

  2. Oxygen; water

  3. Water; oxygen

  4. Water; carbon dioxide
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During the day time, plants lose a lot of water in the form of water vapour due to the process of transpiration. Whereas it takes up carbon dioxide through stomata to carry out photosynthesis.

Hence,the correct answer is 'Water; carbon dioxide'.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

The most important factor for absorption of water in plants is?

  1. Living cell

  2. Force of capillarity

  3. Imbibition

  4. Cohesive force of water
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

While living cells and imbibition play roles, the force of capillarity (and the cohesive-adhesive properties of water) is the primary driver for the movement of water through the xylem in plants.

Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Which is not true regarding active water absorption?

  1. Require energy

  2. Occurs only when transpiration is slow

  3. Living cells are essential

  4. Force develops in shoot
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Active absorption of water occurs in root cells which utilizes the metabolic energy released through respiration. It is of two types. Osmotic absorption is when water is ab­sorbed from the soil into the xylem of the roots according to the osmotic gradient. And Non-osmotic absorption is when water is absorbed against the osmotic gradient. Usually, transpiration is passive absorption but when it is low active absorption occurs. 
  • It takes place in living cells.
  • The force for passive absorption develops in shoot not of active absorption. 

So, the correct answer is 'Force develops in shoot'.
Multiple choice biology transport in plant transport of water and minerals conduction of water and minerals absorption of water and minerals in plants

Which of the following would not contribute to water uptake by plant cell?

  1. an increase in the water potential $\Psi $ of the surrounding solution

  2. a decrease in pressure on the cell exerted by the wall

  3. the uptake of solutes by the cell

  4. an increase in tension on the surrounding solution.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Plant absorb water from the soil by osmosis. Root hair cells are adapted for this by having a large surface area to speed up osmosis. The absorbed water is transported through the roots to the rest of the plant where it's used for different purposes. It's a reactant used in photosynthesis.

So, the correct option is 'an increase in the water potential of the surrounding solution.'