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 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'.
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 may be caused by 

  1. Osmotic flow of water into xylem of absorbing part of root.

  2. Loss of water from xylem of the plant due to transpiration.

  3. Low water potential of leaves.

  4. High water potential of leaves.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When there is no transpiration then due to lack of transpiration pull water does not move upwards. At this time through osmosis water is absorbed from the soil and it accumulates in xylem region of the root .The accumulation through osmosis causes root pressure and water moves upwards.
Thus, the correct option is (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

Root pressure is due to  

  1. Active absorption/ transportation

  2. Passive absorption/ transport

  3. Increased transpiration

  4. Increased photosynthesis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
(A)Active absorption is the absorption of water by roots with the help of ATP.
Root pressure is due to active absorption and active distribution of mineral nutrients. It is measured by potometer.
(B)Passive adsorption is the energy independent process.
(C)Transpiration is the evaporation of water from the upper surface of the leaves.
(D)Photosynthesis is the process of making of glucose.
So, the correct answer is (A) 'Active absorption/ transportation'.
Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

Exudation of xylem sap on cutting of a shoot is due to

  1. Gutttation

  2. Root pressure

  3. Transpiration

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
(A) Guttation is the secretion of droplets from the pores of the tree.
(B) When stem base is cut xylem sap releases and it is due to root pressure [It push the xylem sap upward so when we cut stem base the pulling force of root pressure works].
(C) Transpiration is the evaporation of water from the upper surface of the leaves.
So, the correct answer is 'Root pressure'.
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 at the time of 

  1. Water absorption as well as transpiration.

  2. Both water absorption and transpiration are high.

  3. Absorption is low and transpiration is high.

  4. Absorption is high and transpiration is low.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Root pressure is the negative pressure which helps in the ascent of water. The driving forces for water flow from roots to leaves i.e. root pressure is the lesser force and is important mainly in small plants at times when transpiration is not substantial and absorption is high.
So the correct answer is 'Absorption is high and transpiration is low'.
Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

In the experiment to demonstrate root pressure, where did the cut was made on the plant? 

  1. At the tip

  2. Transition zone

  3. A few centimeters above the soil

  4. A few centimeters below the soil
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Root pressure is the transverse osmotic pressure within the cell of root that causes the rise of sap through the stem of the plant. So, to demonstrate root pressure the cut made is on the shoot just a few centimetres above from the ground.
So, the correct answer is 'A few centimetres above the soil'.
Multiple choice biology absorption by roots - the processes involved root pressure transportation in plants factors affecting the transport of water and minerals in plants

 Passive water absorption by root system is due to 

  1. Force created in roots

  2. Osmotic force In shoot

  3. High respiratory activity of root

  4. Tension in sap due to transpiration.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Transpiration causes a negative pressure region in the xylem . The leaves and other apical parts require huge amounts of water as it is lost in Transpiration. So the stomata takes up the water from the intercellular spaces of the neighbouring cells that in turn draw water from the xylem . Hence a tension or negative pressure region is created in the xylem tissue. This process significantly drops the water potential in the xylem as well as the root region and the water potential of the soil is higher than the roots. So the roots start absorbing water passively as water flows from high water potential to low water potential. Hence Transpiration causes passive absorption of water in roots.

So the correct answer is 'Tension in sap due to 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

Choose the correct answers from the alternatives given.
Which of the following forces pushes water into the xylem as osmosis moves water into the root?

  1. Water stress

  2. Atmospheric pressure

  3. Root pressure

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

Root pressure that is developed in the roots pushes the water into the xylem which is then distributed to different plant parts required for growth.

Water stress is the condition that pushes water to the shoot system but root pressure is the force that required to push water upwards.
Hence,the correct answer is 'Root pressure'.

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

Choose the correct answers from the alternatives given.
Exudation

  1. Takes place during positive root pressure

  2. Takes place during negative root pressure

  3. Is unrelated with root pressure

  4. Is related with photosynthesis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The exudation of liquid drops from the margin of the leaves is called guttation. This happens due to the development of high root pressure as a result of active or more absorption of water at night or early mornings and low transpiration rate. The positive pressure forces the liquid to come out through the special openings called hydathodes.

Hence, the correct answer is 'Takes place during positive root pressure'.

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 most important forces for the ascent of sap in plants are?

  1. Imbibition and capillary

  2. Suction pressure and cohesion

  3. Capillary and root pressure

  4. Root pressure and pulsation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

  • The process by which water and minerals translocate from base to apex of the plant is known as the ascent of sap. It takes place through complex tissue xylem. Most important forces for the ascent of sap are; root pressure and capillary action.
  • Active transport of water takes place through xylem by a pressure called root pressure. It is responsible for pushing up water to small heights in the stem.
  • The tubes in the plant stem are very tiny and the movement of water through tiny tubes is called capillary action. This occurs when the adhesion is stronger than the cohesion. Water molecules are naturally attracted to each other. 


Hence, the correct answer is option C.

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 pressure developed in the root, forces the water into xylem vessel and upwards into the stem for a certain height?

  1. Osmotic pressure

  2. Root pressure

  3. Atmospheric pressure

  4. Turgor pressure
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The pressure with which water is pushed into the xylem tubes of the root is called as root pressure. The water moving upwards forms a column, which is maintained up to a certain height due to root pressure.
In tall trees, trees, this type of absorption plays a minor role in transporting water. This process is slow, and it cannot make up for the water lost by transpiration (the evaporation of water from the leaves). Transpiration is rapid during the day.
The loss of water due to transpiration creates a suction force that pulls water up through the xylem vessels. This transpiration pull serves as the main force that transports water through the xylem. Root pressure helps in the transport of water at night.
So, the correct answer is option B.