0

Significance of transpiration - class-VII

Description: significance of transpiration
Number of Questions: 20
Created by:
Tags: the leaf transpiration transport in plants biology plant physiology botany mineral nutrition in plants
Attempted 0/20 Correct 0 Score 0

Generally, gravitational water is utilized by the plants.

  1. True

  2. False


Correct Option: B
Explanation:
Gravitational water is free water moving through soil by the force of gravity. It is largely found in the macropores of soil and very little gravitational water is available to plants as it drains rapidly down the water table in all except the most compact of soils.

So, the correct answer is 'False'.

Which of the following is not a type of potometer ?

  1. Ganong's

  2. Darwin's

  3. Newton's

  4. None of these


Correct Option: C
Explanation:

Types of Potometer are:-

  • Bubble potometer
  • Mass potometer
  • Ganong's potometer
  • Darwin's potometer

Approx. _______ of the water absorbed by a plant is lost in transpiration.

  1. 20-40%

  2. 98-99%

  3. 1-2%

  4. 6-8%


Correct Option: B
Explanation:

Approx. 98-99% of the water absorbed by a plant is lost in transpiration. Hardly 0.2% is used in photosynthesis while the remaining is retained in the plant during growth.

Significance of transpiration lies in

  1. Circulation of water

  2. Absorption and distribution of water

  3. Regulating the temperature of the plant body

  4. All of the above


Correct Option: D
Explanation:

Transpiration generates tension in plants. This tension is the main pulling force which pulls water to great heights in vascular plants. Thus, transpiration leads to the ascent of sap. Without transpiration water and minerals will not rise from roots to aerial parts of plants and trees. Transpiration also causes surface cooling of leaves and hence regulates the temperature of the plant body. At the same time, it is essentially a wasteful process. As much as 99 percent of water absorbed by a plant goes waste into the atmosphere. Thus, transpiration has been called as a necessary evil.

Exchange of gases occur through 

  1. Stomata

  2. Lenticels

  3. Root surface

  4. All of the above


Correct Option: D
Explanation:

In plants, gas exchange occurs through small pores in the leaf surface called stomata. Stomata can open to allow the exchange of gasses and close to reduce water loss from the plant. In the covering of the secondary structure of the stem of woody plants gas exchange is made through the lenticels of the periderm (small breaches of the cork). The cork of mature roots is also perforated by non-suberized pores called lenticels. These enable oxygen to reach the intercellular spaces of the interior tissues and carbon dioxide to be released into the atmosphere.

Which of the following processes lower the temperature of leaves cooling effect?

  1. Respiration

  2. Photosynthesis

  3. Transpiration

  4. Hydrolysis


Correct Option: C
Explanation:

Transpiration is essentially similar to evaporation of water. It is the loss of water in vapour form through stomata. Water molecules tend to remain in the liquid state rather than moving to vapour state; so during evaporation water molecules absorb a lot of heat energy, this generates a cooling effect.

Plant use _____ % of the absorbed water.

  1. $1$

  2. $10$

  3. $100$

  4. $5$


Correct Option: A
Explanation:

The plant uses only $1\%$ of the absorbed water for its own needs the rest of the water is lost in the atmosphere through 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.


Correct Option: A
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.

Which of the following can regulate the rate of transpiration?

  1. Endodermal cells

  2. Mesothermal cells

  3. Stomata

  4. Roots


Correct Option: C
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.

Water is ideal material for disposal of excess solar energy because

  1. Water is easily available and its specific heat is high

  2. Water evaporates from leaf surface and its latent heat is high

  3. Water is general solvent

  4. Upward movement of water creates a difference in water potential


Correct Option: B
Explanation:

When plants use solar energy for the synthesis of their food, only a small part of solar energy used,  rest of the part of this energy evaporate from the surface of leaves by the process of transpiration and due to its high latent heat. It is the best material for disposing excess  solar energy.

So the correct answer is B. 

In weighing method of transpiration measurement there is

  1. loss of weight by the plant

  2. gain in weight by the plant

  3. No gain, no loss in weight by the plant

  4. All


Correct Option: A
Explanation:

In weighing method of transpiration measurement there is loss in weight b the plant due to loss of water due to 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.


Correct Option: D
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'.

Who said that "transpiration is a necessary evil"?

  1. Bose

  2. Steward

  3. Anderson

  4. Curtis


Correct Option: D
Explanation:

Curtis proclaimed that transpiration is a necessary evil. Stomata allows gaseous exchange. Carbon dioxide is taken in for its fixation by Calvin cycle and oxygen produced during the photolysis is given out. This gaseous exchange takes place by the process of diffusion. When the stomata open for the gaseous exchange, the water vapor is lost by the process of transpiration.

So, the correct answer is option D.

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


Correct Option: B
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.

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 %


Correct Option: D
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.

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


Correct Option: B
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".

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.


Correct Option: B
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.

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


Correct Option: C
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'

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


Correct Option: D
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'.

Choose the correct answers from the alternatives given.
What is the action spectrum of transpiration?

  1. Blue and infra red

  2. Green and ultraviolet

  3. Orange and red

  4. Blue and red


Correct Option: D
Explanation:

An action spectrum is a graph of the rate of a physiological activity plotted against the wavelengths of light. it shows which wavelengths of light is most effectively used in a specific reaction. In photosynthesis, chlorophyll is much more efficient at the blue and red wavelengths of light to carry out photosynthesis. Since transpiration is indirectly related to photosynthesis, its action spectrum would be similar to photosynthesis.

Hence, the correct answer is 'Blue and red'.

- Hide questions