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 botany the leaf mechanism of absorption mineral absorption significance of transpiration

If transpiration stops than

  1. Upward movement of water by roots will stop.

  2. Turgidity of the cells will be not be affected at all.

  3. All metabolic processes will stop.

  4. Upward movement of water by roots will continue and all the metabolic processes will occur as usual.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Most acceptable theory for the ascent of sap is the 'Physical force theory', called as 'Cohesion-Tension' or 'Cohesion-Transpiration pull theory'. This theory was put forward by Dixon and Joly. According to this theory ascent of sap in plants is a physical process, the lifting force for which is provided by the pulling force generated by transpiration. 

The cohesion forces between the water molecules help in maintaining a continuous water column and the adhesion forces between water molecules and the tracheary elements help in sticking to water to the xylary elements. Both of these forces help in maintaining a continuous water column in the xylary elements, which is lifted up by transpiration pull. Hence, if transpiration stops upward movement of water from roots will stop.

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Which of the following can regulate the rate of transpiration?

  1. Endodermal cells

  2. Mesothermal cells

  3. Stomata

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

Stomata can regulate the rate of transpiration by simply controlling how open or closed they are (via the guard cells). Stomata that are open wider will facilitate a greater rate of transpiration, while stomata that are more narrowly opened will reduce the rate of transpiration.

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Choose the correct answers from the alternatives given.
Which of the following is not a part of the transpiration cohesion-adhesion theory of the ascent of xylem sap?

  1. The evaporation of water from the mesophyll cells, which initiates a pull of water molecules from neighbouring cells and eventually from the tracheids

  2. The transfer of this pull from one water molecule to the next due to the cohesion caused by hydrogen bonds

  3. The hydrophilic walls of the narrow tracheids and vessels that help to maintain the column of water against the force of gravity

  4. The use of proton pumps to create membrane potentials that facilitate the accumulation of mineral ions.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The forces of cohesion (attraction among water molecules) and adhesion (attraction between water molecules and the walls of the xylem vessels), together help to form a thin, unbroken column of water which leads to the mass flow of water in apoplastic pathways. These forces act due to the cohesive and adhesive properties of water. In plants, the capillarity is aided by the small diameter of the tracheary elements like the tracheids and the vessel elements. The proton pump has no role in the facilitation of water and minerals.

Hence,the correct answer is 'The use of proton pumps to create membrane potentials that facilitate the accumulation of mineral ions'.

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Grafted flower is contained in saline water because

  1. Suitable nutrient available to flower

  2. Flower remains fresh in long duration due to less transpiration

  3. The flower is protected by microbes

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

Water moves from high water potential to less water potential. Also it is assumed that transpiration loss of water equals water absorption. In saline water there will be less of transpiration loss as absorption will be less. Consequently there are less chances of wilting.

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Generally stomata found on the lower surface of leaf. Thus, approximate percentage of transpiration through abaxial surface is

  1. 47 %

  2. 57 %

  3. 67 %

  4. 97 %
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stomata are usually confined in more number on the lower sides of the leaves. The lower surface is called as abaxial surface and the upper surface is called as the adaxial surface. Hence, maximum percentage i.e., 80- 95% of transpiration occurs from the lower surface.

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Which one is the driving force for the process of passive absorption of water in roots?

  1. Root pressure

  2. Transpiration in leaves

  3. Activity of aquaporins

  4. Increase in imbibition pressure in root cells
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Passive absorption is absorption by the pull from transpiration without the active involvement of root cells, The shoots and leaves of the plant experience transpiration due to evaporation of water from their surface.

So, the answer is, "Transpiration in leaves".

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Transpiration ratio is the ratio of moles of H$ _{2}$O transpired / moles of CO$ _{2}$ fixed. This ratio is measure of

  1. The efficiency of guard cells on stomatal movement.

  2. Effectiveness of stomata is maximizing photosynthesis, while minimizing water loss.

  3. Distinguishing a xerophyte from a glycophyte.

  4. Stomatal pore size of the leaves.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Water is required to generate the reducing power, which is used to reduce carbon dioxide during photosynthesis. The water molecules are split up and oxygen released as a by-product. The protons are used to synthesize reducing power. Now all the water that is absorbed is never used up. In fact, the water that is actually used is a small fraction of water that is absorbed. Hence, transpiration ratio is calculated to find out the effectiveness of stomata in maximizing photosynthesis and minimizing loss of water.

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Water moves up against gravity and even for a tree of $20$m height, the tip receives water within two hours. The most important physiological phenomenon which is responsible for the upward movement of water is ____________.

  1. Cohesive forces

  2. Adhesive forces

  3. Transpiration pull

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

According to transpiration pull theory, due to transpiration, the water column inside the plant comes under tension. This is called 'transpiration pull'. On account of this tension, the water column is pulled up passively from below to top of the plant(almost like a rope). A tension of one atmosphere is sufficient to pull water to a height of about $20$ meters.

So, the correct answer is 'Transpiration pull'

Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

Choose the correct answers from the alternatives given.
Which of the following forces is responsible for moving water up to the tops of the tallest trees?

  1. Atmospheric pressure

  2. Root pressure

  3. Guttation

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

Loss of water from the leaves causes water stress to develop from the top of the trees which forces more and more water to rise from the roots to the leaves. The column of the water is maintained due to cohesion and adhesion forces and the water moves up due to transpiration pull.

Hence,the correct answer is 'Transpiration'.

Multiple choice biology tissues, organs, organ system, organism tissues of animals animal tissues and its type tissues: animal tissues fluid connective tissue

The epidermal cells provide ............ to the plants.

  1. Water

  2. Protection

  3. Strength

  4. All of the above
Reveal answer Fill a bubble to check yourself
B 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, although there are exceptions. The function of epidermal cells are as follows-

1) The epidermal cells protect the underlying cells.
2) The waxy cuticle prevents the loss of moisture from the leaves and stems.
3) The transparent epidermal cells allow sunlight (for photosynthesis) to pass through to the chloroplasts in the mesophyll tissue.
4) The stomata of leaves and stems allow gaseous exchange to take place which is necessary for photosynthesis and respiration.
5) Water vapor may be given off through the stomata during transpiration.
6) The root-hairs absorb water and dissolved ions from the soil.

Multiple choice biology the leaf plant adaptation and modification leaves leaf modification

Which of following is incorrect for trichomes?

  1. Trichomes are leaf modifications which minimize water loss

  2. Usually multicellular

  3. They may even be secretory

  4. Help in water absorption
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • Trichomes are the epidermal outgrowths on the vegetative and reproductive parts of the plant. 
  • These are hair-like structures which may be unicellular or multicellular.
  • Some trichomes are secretory in nature and are known as glandular trichomes. For example, tannins, resins, gum etc., are some products secreted by trichomes.
  • Trichomes help in the absorption of water and minerals.
It is not a leaf modification, hence, option A is incorrect. So, the correct answer is 'Trichomes are leaf modifications which minimize water loss'.

Multiple choice evs roots and leaves plant adaptation and modification leaves leaf modification root, stem, and leaves

Which modified leaf prevents transpiration?

  1. Tendril

  2. Spine

  3. Pitcher

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

A) Tendrils are the modification of leaves that help climbers to climb the support.

C) Spine is the modified structure of entire leaf or part of it that prevent transpiration is xerophytes.
C) Leaf pitcher is the modification of leaf in Nepenthes which takes part in catching and digesting small animals .
So, the correct option is 'Spine'

Multiple choice evs roots and leaves plant adaptation and modification leaves leaf modification root, stem, and leaves

The pulvinus in 'Touch-me-not plant' plays an important role in

  1. Photosynthesis

  2. leaf fall

  3. Leaf movement

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

The leaves close under various other stimuli, such as touching, warming, blowing, or shaking. ... The stimulus can also be transmitted to neighboring leaves. It is not known exactly why Mimosa pudica evolved this trait, but many scientists think that the plant uses its ability to shrink as a defense from herbivores. So, the correct option is "C" (Leaf movement).

Multiple choice zoology excretion to maintain homeostasis other excretory organ role of other organs in excretion accessory excretory organs excretion in other organisms

Which of the following applications illustrates that evaporation leads to cooling?

  1. Perspiration in human body

  2. Transpiration in leaves

  3. Water in earthern post

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

Evaporation or the loss of water from the body due to heat is called as perspiration. The heat present in the surrounding causes water to be lost from the body in the form of sweat through the sweat glands on the skin. The water is deposited on the surface of the organism's body leading to a cooling effect. Thus the correct answer is option A.