Tag: the leaf

Quizzes (12) Questions (128)

Questions Related to the leaf

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

Generally, gravitational water is utilized by the plants.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.
Multiple choice botany the leaf mechanism of absorption mineral absorption significance of transpiration

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
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Exchange of gases occur through 

  1. Stomata

  2. Lenticels

  3. Root surface

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

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

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

  1. Respiration

  2. Photosynthesis

  3. Transpiration

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

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

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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.