Question 21:
What is the main purpose of the stomata in leaves?
A) Gas exchange
B) Water storage
C) Nutrient absorption
D) Photosynthesis
Answer: A) Gas exchange
Explanation: Stomata are tiny openings on the leaf surface that allow for the exchange of gases (CO₂ and O₂) necessary for photosynthesis and respiration.
Question 22:
Which part of the plant is primarily responsible for the absorption of sunlight?
A) Roots
B) Stems
C) Leaves
D) Flowers
Answer: C) Leaves
Explanation: Leaves contain chlorophyll, the pigment that captures sunlight for photosynthesis, making them the primary site for light absorption in plants.
Question 23:
The term “hydrophilic” refers to substances that:
A) Repel water
B) Absorb water
C) Are water-resistant
D) Contain lipids
Answer: B) Absorb water
Explanation: Hydrophilic substances have an affinity for water, meaning they can absorb or interact with water molecules.
Question 24:
Which of the following is a method by which plants can regulate their internal water levels?
A) Stomatal opening and closing
B) Guttation
C) Root pressure
D) All of the above
Answer: D) All of the above
Explanation: Plants regulate water levels through various mechanisms, including the opening and closing of stomata, guttation, and root pressure.
Question 25:
What is the role of companion cells in phloem?
A) Transport water
B) Aid in the transport of sugars
C) Provide structural support
D) Store nutrients
Answer: B) Aid in the transport of sugars
Explanation: Companion cells are associated with sieve elements in phloem and help in the loading and unloading of sugars and nutrients.
Question 26:
The main driving force for the movement of nutrients in phloem is:
A) Root pressure
B) Capillary action
C) Pressure gradient
D) Gravity
Answer: C) Pressure gradient
Explanation: The movement of nutrients in phloem occurs due to the pressure gradient created by the active transport of sugars into the phloem, which leads to the flow of sap from areas of high pressure to low pressure.
Question 27:
What type of cells in xylem are primarily responsible for water transport?
A) Sieve tubes
B) Tracheids
C) Companion cells
D) Parenchyma
Answer: B) Tracheids
Explanation: Tracheids are elongated cells in xylem that facilitate the conduction of water and minerals through their perforated walls.
Question 28:
Which process describes the movement of water through the xylem by cohesion?
A) Transpiration
B) Capillary action
C) Root pressure
D) Osmosis
Answer: B) Capillary action
Explanation: Capillary action occurs due to cohesion (water molecules sticking to each other) and adhesion (water molecules sticking to the xylem walls), allowing water to rise in narrow tubes.
Question 29:
Which part of the plant primarily experiences the highest rate of transpiration?
A) Roots
B) Flowers
C) Stems
D) Leaves
Answer: D) Leaves
Explanation: Leaves have a large surface area and numerous stomata, making them the primary site for transpiration, where water vapor exits into the atmosphere.
Question 30:
In which of the following conditions is transpiration most likely to be highest?
A) Cool and humid
B) Hot and dry
C) Overcast
D) Cold and wet
Answer: B) Hot and dry
Explanation: High temperatures and low humidity increase the rate of water evaporation from the leaf surface, resulting in higher transpiration rates.
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