Q41. Which of the following substances is primarily transported through the phloem in plants?
a) Sugars
b) Amino acids
c) Water
d) Plant hormones
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Correct Answer: a) Sugars
Explanation: The phloem in plants primarily transports organic nutrients, such as sugars produced during photosynthesis, from source tissues (like leaves) to sink tissues (such as roots, fruits, and developing seeds). Along with sugars, phloem also transports other organic compounds like amino acids and certain plant hormones.
Q42. What is the primary function of the epidermis in plant leaves?
a) Photosynthesis
b) Gas exchange
c) Protection
d) Water absorption
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Correct Answer: c) Protection
Explanation: The epidermis is the outermost layer of cells in plant leaves, stems, and roots. Its primary function is to provide protection against physical damage, pathogens, and water loss. The epidermis in leaves also contains specialized structures such as stomata and trichomes.
Q43. Which of the following processes involves the movement of sugars and other organic nutrients from source tissues to sink tissues in plants?
a) Transpiration
b) Respiration
c) Translocation
d) Photosynthesis
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Correct Answer: c) Translocation
Explanation: Translocation is the process by which sugars and other organic nutrients synthesized in source tissues (such as leaves) are transported to sink tissues (such as roots, fruits, and developing shoots) in plants through the phloem. This process is essential for distributing energy and nutrients throughout the plant.
Q44. What is the term for the process by which excess salts and minerals are removed from the plant’s vascular system and deposited in leaves or other tissues?
a) Transpiration
b) Guttation
c) Excretion
d) Accumulation
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Correct Answer: c) Excretion
Explanation: Excretion in plants involves the removal of excess salts, minerals, and metabolic wastes from the plant’s vascular system. These substances are deposited in leaves or other tissues, helping to regulate osmotic balance, prevent toxicity, and maintain proper nutrient levels.
Q45. Which of the following is a specialized tissue in plant leaves responsible for photosynthesis?
a) Epidermis
b) Xylem
c) Phloem
d) Mesophyll
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Correct Answer: d) Mesophyll
Explanation: Mesophyll is a specialized tissue in plant leaves that contains chloroplast-rich cells responsible for photosynthesis. It consists of two layers: the palisade mesophyll, located beneath the upper epidermis, and the spongy mesophyll, located beneath the palisade layer.
Q46. What is the primary function of the guard cells in plant leaves?
a) Photosynthesis
b) Gas exchange
c) Water absorption
d) Nutrient transport
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Correct Answer: b) Gas exchange
Explanation: Guard cells are specialized cells found in the epidermis of plant leaves and stems, surrounding stomatal pores. Their primary function is to regulate gas exchange by controlling the opening and closing of stomata in response to environmental cues such as light intensity, humidity, and carbon dioxide levels.
Q47. What is the term for the process by which plants release oxygen into the atmosphere as a byproduct of photosynthesis?
a) Respiration
b) Transpiration
c) Excretion
d) Evaporation
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Correct Answer: a) Respiration
Explanation: Respiration in plants involves the release of oxygen into the atmosphere as a byproduct of photosynthesis. During photosynthesis, plants use carbon dioxide and water to produce glucose and oxygen. The oxygen released during this process is utilized by plants and other organisms for cellular respiration.
Q48. Which of the following substances is NOT transported through the phloem in plants?
a) Sugars
b) Amino acids
c) Water
d) Plant hormones
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Correct Answer: c) Water
Explanation: The primary function of the phloem in plants is the transport of organic nutrients, primarily sugars (such as glucose and sucrose), from source tissues (like leaves) to sink tissues (such as roots, fruits, and developing seeds). Water is primarily transported through the xylem.
Q49. What is the primary function of lenticels in plants?
a) Gas exchange
b) Water absorption
c) Photosynthesis
d) Nutrient transport
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Correct Answer: a) Gas exchange
Explanation: Lenticels are small, raised areas on the bark of woody stems and roots that facilitate gas exchange between internal tissues and the external environment. They allow oxygen to enter the plant and carbon dioxide to exit, particularly in tissues where the epidermis is impermeable to gases.
Q50. Which of the following substances is primarily transported through the xylem in plants?
a) Sugars
b) Amino acids
c) Water and minerals
d) Plant hormones
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Correct Answer: c) Water and minerals
Explanation: The primary function of the xylem in plants is the transport of water and minerals absorbed by the roots from the soil to other parts of the plant, including the leaves and stems. Xylem vessels provide structural support and facilitate the upward movement of water through capillary action.