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 multicellular structure: tissue defense mechanism in plants epidermal tissue system kinds of plant tissue permanent tissues and their types

Motor cells help in

  1. Inward rolling of leaves

  2. Transpiration

  3. Guttation

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

Bulliform cells or motor cells are large, bubble-shaped epidermal cells that occur in groups on the upper surface of the leaves of many grasses. Loss of turgor pressure in these cells causes leaves to roll up during water stress. During drought, the loss of moisture through vacuoles induces bulliform cells to cause the leaves of many grass species to close as the two edges of the grass blade fold up toward each other. Once adequate water is available, these cells enlarge and the leaves open again. Folded leaves offer less exposure to sunlight, so they are heated less thus, reducing evaporation and conserving the remaining water in the plant and occur on the leaves of many monocotyledons but are probably best known in grasses. They are thought to play a role in the unfolding of developing leaves and in the rolling and unrolling of mature leaves in response to alternating wet and dry periods. So, motor cells helps in inward rolling of leaves and not in transpiration or guttation. 
Thus, the correct answer is option A.

Multiple choice biology multicellular structure: tissue defense mechanism in plants epidermal tissue system kinds of plant tissue permanent tissues and their types

In respect of many grasses, the presence of motor cells in the upper epidermis of leaves is to

  1. Increase the surface area of the leaf

  2. Store large amount of water

  3. Check transpiration by reducing the surface area of the leaf

  4. Bear unicellular trichomes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Bulliform cells or motor cells are large, bubble-shaped epidermal cells that occur in groups on the upper surface of the leaves of many grasses. Loss of turgor pressure in these cells causes leaves to roll up during water stress. During drought, the loss of moisture through vacuoles induces bulliform cells to cause the leaves of many grass species to close as the two edges of the grass blade fold up toward each other. Once adequate water is available, these cells enlarge and the leaves open again. Folded leaves offer less exposure to sunlight, so they are heated less thus, reducing evaporation and conserving the remaining water in the plant and occur on the leaves of many monocotyledons but are probably best known in grasses
So, the correct answer is 'Check transpiration by reducing the surface area of the leaf'
Multiple choice biology multicellular structure: tissue defense mechanism in plants epidermal tissue system kinds of plant tissue permanent tissues and their types

Which of following tissues do you expect to be the most important during droughts and why?

  1. Vascular tissue because phloem regulates water supply to the plant

  2. Ground tissue because water can be stored in sclerenchyma for use during drought

  3. Epidermal tissue because it is covered with a waxy cuticle and also bears drought responsive stomata

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

The epidermis is the outermost cellular layer which covers the whole plant structure, i.e. it covers roots, stem, leaves, flowers, and fruit. It is composed of a single layer of living cells. The outer walls, which are exposed to the atmosphere and usually thickened, are covered by a waxy, waterproof cuticle which is made up of cutin. The waxy cuticle prevents the loss of moisture from the leaves and stems. During drought, the plant hormone abscisic acid (ABA) triggers stomatal closure, thus reducing water loss.

So, the correct answer is option C.

Multiple choice bio-chemistry biological oxidation chemiosmotic hypothesis living organisms and energy production mechanism of photosynthesis

Read the following statements and find out the incorrect statement.

  1. Glucose is prepared at the source by photosynthesis which is converted to sucrose

  2. Loading at the source produces a hypotonic condition in phloem

  3. Loading of the phleom sets up a water potential gradient that facilitates the mass movement in the water

  4. Phloem tissue is composed of sieve tube cells, which form long columns with holes in their end walls called sieve plates
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice biology through the alimentary canal guttation excretion in plants long distance transport of water

Plants excrete gases through 

  1. Microscopic pores in leaves.

  2. Small porous roots.

  3. Flowers.

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

Plants eliminate some waste through diffusion. During the day, excess oxygen gas produced by photosynthesis is released through the stomata. Stomata are microscopic pores in leaves. Carbon dioxide produced by respiration is normally used up during photosynthesis. At night, however, as photosynthesis slows, carbon dioxide is not used up as fast as it is produced, and it is released as a waste product. Plants also produce oxygen as a by-product of photosynthesis. The oxygen that is not used for respiration is also excreted through the stomata. Plants do not excrete gases through flowers, roots and seeds. 

Therefore, the correct answer is option A.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Which condition favors guttation?

  1. High humidity

  2. Low humidity

  3. More transpiration

  4. Bright sunlight
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Guttation is the phenomenon of the release of small water droplets from the pores of the plants. It is done in order to release the extra water out of the plant in very humid conditions. It is commonly seen in mesophytes.

During the absence of sunlight stomata are closed so there is minimal transpiration. Hence there is a need for guttation.
So the correct answer is 'High humidity'.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Loss of water from tips of leaves is 

  1. Transpiration

  2. Guttation

  3. Bleeding

  4. Respiration
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Guttation is the process of loss of impure water from plant infact, mostly from margins of leaves. It occurs when transpiration rate is very low as compared to rate of water absorption. Due to this root pressure is developed and water is pushed out through specialized pores at vein endings called hydathodes. 
So, the correct answer is option B.
Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Water drops present on leaf margins of Tropaeolum, balsam and grasses in early morning are due to

  1. Guttation

  2. Dew

  3. Osmosis

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

Guttation is the loss of water in liquid form through hydathodes. Guttation is usually seen under environmental conditions when transpiration is low and soil is well watered. It occurs under the influence of positive root pressure. Water droplets present on leaf margins of some plants in the early morning is not due drops but the water that has oozed out from xylem tracheids. 

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Guttation drops can be differentiated from dew drops

  1. By taste

  2. As dew drops will be seen

  3. As guttation drops will be restricted on the margins of the leaf

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

Guttation is the loss of water in liquid form through hydathodes. Guttation is usually seen under environmental conditions when transpiration is low and soil is well watered. It occurs under the influence of positive root pressure. Water droplets present on leaf margins of some plants in the early morning is not due drops but the water that has oozed out from xylem tracheids. Xylem tracheids contain dissolved minerals in the water. Hence water lost in guttation is not pure water but a solution of minerals and will not be tasteless as the pure water of dew drops.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Loss of water from tips of leaves is called as

  1. Bleeding

  2. Guttation

  3. Respiration

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

Loss of water in vapour form through stomata is called as transpiration. Loss of water in solution form through vein endings in leaves is called as guttation. Transpiration occurs under the influence of vapour pressure gradient. Guttation is caused due to root pressure when soil is well watered and transpiration is low due to high atmospheric humidity.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Which of the following is not a rhythmic phenomenon?

  1. Stomatal opening and closing

  2. Guttation

  3. Nyctinasty

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

The movements showed by plants can be classified broadly as
(1) Hygroscopic- due to loss or gain of water and
(2) Vital- due to irritability of the cytoplasm. 
Nyctinasty or sleep movements are rhythmic movements, also called as sleep movements and are caused by relative changes in cell size on the opposite sides of the leaf base called as pulvinus. 

Photonasty is the nastic movement caused in response to light. 
Guttation is the loss of water in solution through hydathodes. This is not an example of rhythmic movement and depends on environmental conditions. Thus, the correct answer is option B.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Which condition favours guttation?

  1. High water absorption

  2. High transpiration

  3. Low transpiration

  4. Both A and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Guttation is the loss of water through water stomata (hydathodes) in solution form as a dilute solution of mineral salts. This process occurs, when the absorption of water exceeds transpiration i.e., when plants are absorbing water actively. A positive root pressure is built up under the influence of which excess water simply oozes out through the dead ends of xylem tracheids and vessels. Thus, the correct answer is option D.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Guttation usually occur in a well watered herbaceous plant and well drained soil during

  1. Early morning hours

  2. Evening hours

  3. Noon hours

  4. Day hours
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Guttation is the loss of water through water stomata (hydathodes) in the form of the dilute solution of mineral salts. When the absorption of water exceeds transpiration i.e., when plants are absorbing water actively, a positive root pressure is built up under the influence of which excess water simply oozes out through the dead ends of xylem tracheids and vessels. This usually happens during early morning hours when transpiration is low.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

Guttation occurs when plants absorb water through

  1. Active absorption

  2. Passive absorption

  3. Root pressure

  4. Both A and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When the plant absorbs water by their own, it is called active absorption. It takes place when transpiration is low and amount of water in the soil is high. In this case root hairs play the major role in the absorption of water. Root pressure is the positive pressure that develops in the roots of plants by the active absorption of nutrients from the soil. It causes sap to rise through a plant stem to the leaves. Guttation is the exudation of xylem sap on the tips or edges of leaves of some vascular plant. According to the passive absorption, root hairs do not play any role in absorption. It takes place only when transpiration rate is high. So, the correct option is D.