Absorption by Roots & Transpiration Quiz - ICSE Class 10 Biology
Free practice quiz: Absorption by Roots & Transpiration (ICSE Class 10 Biology). 35 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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A plant is subjected to an environment with extremely low humidity and high wind speeds. Which of the following adaptations would be most crucial for its survival to minimize water loss through transpiration?
- Large, broad leaves with numerous stomata
- Thick cuticle and sunken stomata
- Extensive root system with numerous root hairs
- Presence of hydathodes
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Answer: B. Thick cuticle and sunken stomata
A thick cuticle acts as a barrier to water loss, and sunken stomata create a humid microenvironment around the stomatal pore, reducing the water potential gradient and thus transpiration. Large leaves and numerous stomata increase transpiration. Extensive root systems are for absorption, not reducing loss. Hydathodes are involved in guttation, not stomatal transpiration.
The rate of transpiration can be significantly reduced by applying a thin layer of oil on the surface of leaves. What is the primary reason for this reduction?
- The oil increases the water potential of the leaf.
- The oil blocks the stomatal pores, preventing gas exchange and water vapor diffusion.
- The oil directly inhibits the activity of xylem vessels.
- The oil stimulates the closure of guard cells.
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Answer: B. The oil blocks the stomatal pores, preventing gas exchange and water vapor diffusion.
Transpiration primarily occurs through stomata. A layer of oil effectively seals these pores, preventing the outward diffusion of water vapor and also inhibiting the inward diffusion of CO2 needed for photosynthesis. It doesn't directly affect xylem or guard cell function in this manner.
The primary function of root hairs in a plant is:
- To anchor the plant firmly in the soil.
- To absorb water and dissolved minerals from the soil.
- To store food reserves for the plant.
- To transport sugars from the leaves to the roots.
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Answer: B. To absorb water and dissolved minerals from the soil.
Root hairs are thin, hair-like extensions of epidermal cells in the root. They greatly increase the surface area of the root, maximizing the absorption of water and dissolved mineral nutrients from the soil.
If a plant leaf is observed to have wilting symptoms, but the surrounding soil is moist, what could be the primary reason?
- Excessive absorption of mineral salts.
- High rate of transpiration exceeding water absorption.
- Low rate of photosynthesis.
- Reduced root pressure.
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Answer: B. High rate of transpiration exceeding water absorption.
Wilting occurs when water loss from the plant (transpiration) is greater than water uptake by the roots. Even if the soil is moist, if transpiration is very high (e.g., due to hot, dry, windy conditions), the plant can wilt because it cannot absorb water fast enough to replace the lost water.
Which of the following is a direct consequence of reduced stomatal aperture?
- Increased rate of photosynthesis.
- Increased absorption of water by roots.
- Decreased rate of transpiration.
- Increased uptake of mineral ions.
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Answer: C. Decreased rate of transpiration.
The stomatal aperture is the opening size of the stoma. Reducing this aperture limits the diffusion of water vapor out of the leaf, thereby decreasing the rate of transpiration. It also limits CO2 uptake, affecting photosynthesis.