Biology

Plant Transport and Physiology

2,012 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 cell-the basic unit of life number and shape of cells unicellular and multicellular organisms cell parameters diversity and classification in animals

Which of the following statement are false?
(a) Most cells are tiny with volume range of $1-100$ $n{m}^{3}$
(b) Some cells have microvelli to increase the absorptive surface area.
(c) All cells arise from pre-existing cells.
(d) In plants, translocation of solutes is performed by xylem vessels and tracheids.
(e) According to cell theory, all cells arise from abiotic material.

  1. a), c) and e) are false.

  2. a), d) and e) are false.

  3. b), c) and d) are false.

  4. c), d) and e) are false.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement (a) is false because cells are typically in the micrometer range, not nanometers. Statement (d) is false because translocation of solutes (phloem) is performed by phloem, not xylem. Statement (e) is false because cell theory states cells arise from pre-existing cells, not abiotic material.

Multiple choice biology respiration and energy transfer respiratory quotient-basic respiration-plants respiratory quotient

In succulents, respiratory quotient is less than one due to

  1. Incomplete oxidation

  2. Incomplete reduction

  3. Complete reduction

  4. Complete oxidation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Where incomplete oxidation of carbohydrates takes place R.Q is zero. In such cases oxygen absorbed does not oxidise the carbohydrates completely to carbon dioxide and water.
This occurs especially in respiration of succulent plants. In such plants respiration of carbohydrates occurs at night when stomata are open which results in the production of organic acids that utilise O₂ but do not evolve CO₂.
So, the correct option is 'Incomplete oxidation'
Multiple choice biology respiration and energy transfer respiratory quotient-basic respiration-plants respiratory quotient
Value of R.Q. in succulents is ____________.

  1. Unity

  2. Infinite

  3. Less than unity

  4. Zero
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Succulents do not evolve carbon dioxide during the night (when their stomata are open) as the same is in carbon fixation. They also change carbohydrates to organic acids which utilise oxygen but do not evolve carbon dioxide.

${2C} _{6}{H} _{12}{O} _{6}+{3O} _{2}\longrightarrow\underset {Malic \,acid}{{3C} _{4}{H} _{6}{O} _{5}}+{3H} _{2}O$
$R.Q.=\frac{Zero\,{CO} _{2}}{{3O} _{2}}=Zero$
So the correct option is D.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Root pressure is due to?

  1. Diffusion

  2. Passive transport

  3. Active transport

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

Root pressure is developed due to the active absorption of ions from the soil by root cells. This creates an osmotic gradient that draws water into the root xylem, requiring metabolic energy in the form of active transport.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

The cause of guttation is mainly due to

  1. Root pressure

  2. Osmosis

  3. Transpiration pull

  4. Cohesive force
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Guttation is a loss of water from plants in liquid form through hydathodes. The force responsible for guttation is positive root pressure. Guttation is easily observed when transpiration rate is low and soil is well watered.

So, the correct answer is option A.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

The pressure exerted on the fluid contents of the cortical cells of root by turgidity, which forces the water into xylem vessels and upward into stem for a certain height is

  1. Imbibition

  2. Root pressure

  3. Capillarity

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

Root pressure helps to pull the cell sap through a plant stem to the leaves. It occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day.

So, the correct answer is option B.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Root pressure in maximum, when

  1. Transpiration is high and absorption is very low.

  2. Transpiration is very low and absorption is high.

  3. Absorption is very high and transpiration is also very high.

  4. Absorption is very low and transpiration is also low.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When transpiration is low and soil is generally well watered, a positive root pressure develops. Under the influence of positive root, pressure water oozes out from ends of xylary elements in plants. The main reason for the development of positive root pressure is the active absorption of minerals and water by roots.

So, the correct answer is option B.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Guttation is dependent on

  1. Root pressure

  2. Active absorption

  3. Flaccidity of root cortical cells

  4. High rate of transpiration
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Transpiration is defined as loss of water as gas or vapors from aerial parts, like leaves through the stomatal pore. If there is less of transpiration as due to high atmospheric humidity and the soil is well watered; there will be an increase in root pressure. The increased root pressure leads to oozing out of a solution of minerals from hydathodes (called as guttation) and other openings (called as bleeding). 

So, the correct answer is option A.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Pressure caused by water entering the root from soil is known as

  1. Imbibition

  2. Root pressure

  3. Turgor pressure

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

Root pressure can be defined as the pressure exerted by the cortical cells of the root upon the sap in the xylem vessels which pushes the sap upward if the stem of the plant is cut just above the root water seeps or exudes out of the cut end of the stem for a considerable period of time. This indicates that there is a force pushing water up the stem from the roots.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Root pressure helps in


i Continuous flow of water in plants
ii Pulling force
iii Replacement of lost water

  1. i, ii

  2. ii, iii

  3. i, iii

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

Root pressure provides a force which causes pushing of water in a stem. A continuous flow of water is maintained in the plants because the leaves transpire water through stomata and to replace the lost water the water drawn by the roots moves up.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

If the stem of the plant is cut just above the root then

  1. Water will seep or exude out of the cut end for a considerable amount of time.

  2. Water will seep or exude out of the cut end continuously

  3. Both A and B

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

Root pressure can be defined as the pressure exerted by the cortical cells of the root upon the sap in the xylem vessels which pushes the sap upwards if the stem of the plant is cut just above the root, water seeps or exudes out of the cut end of the stem for a considerable period of time. This indicates that there is a force pushing water up the stem from the roots.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Root pressure is maximum when

  1. Transpiration is high and absorption low

  2. Transpiration is very low and absorption is high

  3. Transpiration is very high and absorption is high

  4. Transpiration and absorption both are slow
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Root pressure is the positive pressure that develops in the roots of the plants by active absorption of nutrients from the soil. The active absorption depends on the active accumulation of solute in xylem sap. Root pressure in maximum when transpiration is very low and absorption is high because transpiration is the output of water from a plant, and absorption is the input of water into a plant. If the output is low and input is high, the pressure will be at its greatest. 

So, the correct answer is 'Transpiration is very low and absorption is high'.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Root pressure is maximum when

  1. Transpiration is high and absorption is very low

  2. Transpiration is very low and absorption is high

  3. Transpiration is very high and absorption is also high

  4. Transpiration and absorption both are slow
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Stephentiales (1727) coined the term root pressure. Root pressure is developed when rate of water absorption is more than the rate of transpiration.

Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Which of the following statement is wrong in root-presure concept of ascent of sap ?

  1. Water can be raised to a height of 6'-7'.

  2. Water moves upward in the absence of shoot.

  3. Water moves by this force is slow.

  4. Root pressure operates in all the plants.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Root pressure is not operated in lower plants and plants of small height and aquatic plants because they have several other mechanisms to conduct water. Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day.
So the correct answer is 'Root pressure operates in all the plants'.