Free Forms and Functions of Plants MCQs with Answers

111. The volume of dry seed increased by imbibitions is _ times.

• A. 100 times
• B. 200 times
• C. 300 times
• D. 150 times

Explanation: The correct answer is "200 times." During the process of imbibition, seeds absorb a significant amount of water, causing their volume to increase substantially, typically around 200 times. This expansion is essential for breaking the seed coat, allowing germination to proceed. Option A (100 times) and Option D (150 times) underestimate the typical increase, while Option C (300 times) overestimates the increase.

112. 1% of the absorbed water is used by plants in its activities during:

• A. Metabolism
• B. Respiration
• C. Photosynthesis
• D. Vernalization

Explanation: The correct answer is Photosynthesis. During photosynthesis, plants use about 1% of the absorbed water to convert carbon dioxide and light into glucose and oxygen. This process is critical for plant growth and energy production. Other options, like metabolism and respiration, involve water, but they do not specifically use 1% of the absorbed water. Vernalization is unrelated to water usage as it pertains to the flowering process induced by cold exposure.

113. Pick up the types of transpiration which do not occur in all plants:

• A. Cuticular transpiration
• B. Stomatal transpiration
• C. Lenticular transpiration
• D. None of these

Explanation: The correct answer is Lenticular transpiration. This type of transpiration occurs through lenticels, which are unique to woody plants and not present in all plants. In contrast, cuticular and stomatal transpiration are more widespread across plant species. Although stem transpiration can occur, it is not a universal characteristic and does not account for a significant amount of transpiration in most plants.

114. Which one of the following is involved in the closing of stomata?

• A. Gibberellins
• B. Ethylene
• C. Abscisic acid
• D. Cytokinins

Explanation: The correct answer is Abscisic acid. Abscisic acid (ABA) is a plant hormone that plays a critical role in regulating the closure of stomata, particularly in response to drought stress. When plants experience water deficiency, ABA is synthesized in the leaves, leading to the closure of stomata to minimize water loss. In contrast, Gibberellins and Cytokinins are primarily involved in growth and developmental processes, while Ethylene is associated with fruit ripening and stress responses, but not specifically with stomatal closure.

115. When leaves transpire the water potential of mesophyll cells is:

• A. Increased
• B. Does not change
• C. Decreased
• D. First increased and then decreased

Explanation: The correct answer is "Decreased." When leaves transpire, they lose water vapor, which decreases the water potential of the mesophyll cells. This decrease creates a negative water potential gradient that draws water from the xylem into the mesophyll cells to replace the lost water. The other options are incorrect because they either misinterpret the effect of transpiration on water potential or describe processes not directly related to the primary impact of transpiration.

116. Average velocity of movement of sugars in phloem is:

• A. 1 meter/8 years
• B. 1 meter/day
• C. 1 meter/hour
• D. 20 cm/min

Explanation: The correct answer is "1 meter/hour" because studies have shown that the average velocity of sugar transport in the phloem is approximately 1 meter per hour. This rate allows for effective distribution of nutrients throughout the plant. Option A significantly underestimates the rate, making it impractical for plant function. Option B, while plausible under some conditions, generally underestimates typical rates. Option D suggests a much faster rate than is commonly observed, which can occur but is not the average.

117. The most widely accepted explanation for the ascent of sap in trees is

• A. Capillarity
• B. Role of atmospheric pressure
• C. Pulsating action of living cells
• D. Transpiration cohesion theory of Dixon

Explanation: The transpiration cohesion theory states that water molecules in the xylem of a tree are held together by cohesion, or the attraction between water molecules. The water molecules are also attracted to the walls of the xylem vessels, creating tension. The tension in the water column is what pulls the water up the tree.

118. The attraction between water molecules and cell wall of xylem is termed as :

• A. Adhesion
• B. Cohesion
• C. Capillary action
• D. Transpiration

Explanation: This is the correct answer. Adhesion refers to the attraction between molecules of different substances. In the case of xylem, the water molecules are attracted to the cellulose molecules in the cell walls. This adhesive force helps to pull water up the xylem vessels from the roots to the leaves.

119. Dark reaction of photosynthesis takes place:

• A. Grana
• B. Stroma
• C. Thylakoid
• D. Both grana and stroma

Explanation: Dark reactions (light-independent reactions) of photosynthesis take place in the stroma of chloroplasts.

120. Brassica and rose plant belong to the group of plants:

• A. Hydrophytes
• B. Mesophytes
• C. Xerophytes
• D. Succulant

Explanation: Brassica belongs to the cabbage family while rose belongs to the rose family.