Q21. What type of roots are known to form a symbiotic relationship with nitrogen-fixing bacteria in leguminous plants?
a) Fibrous roots
b) Taproots
c) Adventitious roots
d) Nodular roots
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Correct Answer: d) Nodular roots
Explanation: Nodular roots in leguminous plants form a symbiotic relationship with nitrogen-fixing bacteria, such as Rhizobium. These specialized roots have nodules where bacteria live and convert atmospheric nitrogen into a form that the plant can use for growth. This process enriches the soil with nitrogen, benefiting the plant and its environment.
Q22. What is the main function of xylem in plants?
a) Transporting nutrients
b) Conducting water and minerals
c) Producing food through photosynthesis
d) Absorbing sunlight
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Correct Answer: b) Conducting water and minerals
Explanation: The main function of xylem in plants is to conduct water and dissolved minerals from the roots to other parts of the plant. Xylem consists of hollow vessels that facilitate the upward movement of water through capillary action, playing a crucial role in the plant’s water and nutrient transport system.
Q23. Which part of the plant is involved in the exchange of gases?
a) Roots
b) Flowers
c) Leaves
d) Stems
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Correct Answer: c) Leaves
Explanation: Leaves are primarily involved in the exchange of gases in plants. They contain tiny openings called stomata, through which carbon dioxide enters for photosynthesis, and oxygen, a byproduct of photosynthesis, exits. Stomata also facilitate the release of water vapor, a process known as transpiration.
Q24. In which layer of the leaf does most photosynthesis occur?
a) Epidermis
b) Cuticle
c) Mesophyll
d) Vascular bundle
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Correct Answer: c) Mesophyll
Explanation: Most photosynthesis occurs in the mesophyll layer of the leaf. This layer contains the majority of the plant’s chloroplasts, the organelles where photosynthesis takes place. The mesophyll is typically divided into two parts: the palisade mesophyll, where most of the photosynthesis occurs, and the spongy mesophyll, which assists in gas exchange.
Q25. Which of the following is a characteristic of hydroponic farming?
a) Use of soil for plant growth
b) Growing plants in a water-based nutrient solution
c) Relying on rainwater for irrigation
d) Utilizing natural sunlight only
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Correct Answer: b) Growing plants in a water-based nutrient solution
Explanation: Hydroponic farming is characterized by growing plants in a water-based nutrient solution, without the use of soil. Plants are supported in an inert medium like perlite, rock wool, or clay pellets, and a nutrient-rich solution is delivered directly to the roots. This method allows for efficient nutrient management and often results in higher yield and faster growth.
Q26. What is the name of the process by which plants lose water vapor from their aerial parts, mainly leaves?
a) Photosynthesis
b) Transpiration
c) Respiration
d) Evaporation
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Correct Answer: b) Transpiration
Explanation: Transpiration is the process by which plants lose water vapor from their aerial parts, primarily leaves. It occurs when water is absorbed by roots and transported to leaves, where it is then lost as vapor through stomata. This process helps in the movement of water and nutrients from the roots to the leaves and also aids in cooling the plant.
Q27. In the context of plant nutrition, what is the role of mycorrhizae?
a) Fixing atmospheric nitrogen
b) Decomposing organic matter
c) Enhancing water and nutrient absorption
d) Protecting plants from herbivores
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Correct Answer: c) Enhancing water and nutrient absorption
Explanation: Mycorrhizae, a symbiotic association between a fungus and plant roots, play a significant role in enhancing water and nutrient absorption. The fungi extend the root system’s reach, allowing the plant to access a larger volume of soil and thus absorb more water and nutrients, particularly phosphorus.
Q28. Which process is primarily used by cacti and other succulents to reduce water loss?
a) C3 photosynthesis
b) C4 photosynthesis
c) CAM (Crassulacean Acid Metabolism) photosynthesis
d) Chlorophyll fluorescence
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Correct Answer: c) CAM (Crassulacean Acid Metabolism) photosynthesis
Explanation: CAM (Crassulacean Acid Metabolism) photosynthesis is a process used by cacti and other succulents to reduce water loss. In this process, the stomata in the leaves remain closed during the day to reduce water loss and open at night to collect carbon dioxide. The CO2 is then stored and used during the day for photosynthesis.
Q29. What is the main role of phosphorus in plant nutrition?
a) Enhancing root growth
b) Aiding in photosynthesis
c) Contributing to cell division
d) Facilitating energy transfer
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Correct Answer: d) Facilitating energy transfer
Explanation: Phosphorus plays a key role in plant nutrition by facilitating energy transfer within the plant. It is a part of ATP (adenosine triphosphate), the energy currency of the cell, and is involved in several key processes like photosynthesis, nutrient transport, and cell division. Phosphorus is also vital for the development of roots and flowers.
Q30. What is allelopathy in plants?
a) Mutual sharing of nutrients
b) Competing for sunlight
c) Producing chemicals to inhibit the growth of neighboring plants
d) Forming symbiotic relationships with animals
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Correct Answer: c) Producing chemicals to inhibit the growth of neighboring plants
Explanation: Allelopathy refers to the production of biochemicals by plants, known as allelochemicals, that influence the growth, survival, and reproduction of neighboring plants. These chemicals can be beneficial or harmful, but in many cases, they inhibit the growth of surrounding vegetation, reducing competition for resources.