वनस्पति विज्ञान – Botany – Botany MCQ
वनस्पति विज्ञान – Botany – CEE प्रवेश
Botany · Medical Entrance (CEE) – Physics, Chemistry, Biology & MAT · ४०७ प्रश्न
४०७ प्रश्न उपलब्ध। मोड छान्नुहोस्:
वनस्पति विज्ञान – Botany: प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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Which micronutrient is a component of the enzyme nitrogenase?
सही उत्तर: ख) Molybdenum
Molybdenum (along with iron) is a component of nitrogenase and also of nitrate reductase. Zinc is needed for auxin synthesis.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The pink colour of root nodules of leguminous plants is due to:
सही उत्तर: ग) Leghaemoglobin
Leghaemoglobin binds oxygen and protects nitrogenase from inactivation. Anthocyanins give red-purple colours to flowers and fruits, not root nodules.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The enzyme responsible for biological nitrogen fixation is:
सही उत्तर: ख) Nitrogenase
Nitrogenase reduces atmospheric N2 to ammonia and is sensitive to oxygen. Nitrate reductase reduces nitrate to nitrite, which is a different step.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The pressure flow (mass flow) hypothesis for translocation of food in phloem was proposed by:
सही उत्तर: ग) Münch
Ernst Münch proposed that sugars move from source to sink driven by a turgor pressure gradient. Dixon and Joly's theory concerns water movement in xylem.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The cohesion–tension (transpiration pull) theory of ascent of sap was proposed by:
सही उत्तर: ग) Dixon and Joly
Dixon and Joly explained ascent of sap by cohesion, adhesion and transpiration pull. Münch proposed the pressure flow hypothesis for phloem translocation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Opening of stomata is mainly associated with the influx of which ion into guard cells?
सही उत्तर: ग) Potassium (K+)
Uptake of K+ lowers the water potential of guard cells, water enters, and they become turgid, opening the pore. Loss of K+ leads to stomatal closure.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Guttation (loss of water as droplets) occurs through:
सही उत्तर: घ) Hydathodes
Guttation occurs through hydathodes at leaf margins due to root pressure, often seen in grasses in the early morning. Stomata release water as vapour.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A plant cell placed in a hypertonic solution will undergo:
सही उत्तर: ख) Plasmolysis
In a hypertonic solution water leaves the cell, and the protoplast shrinks away from the cell wall (plasmolysis). In a hypotonic solution the cell becomes turgid instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The water potential of pure water at standard temperature and pressure is:
सही उत्तर: ग) Zero
By convention, pure water has the highest water potential, taken as zero. Adding solutes lowers it, so solutions have negative water potential.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Xylem vessels are generally absent in:
सही उत्तर: क) Gymnosperms
Gymnosperm xylem consists mainly of tracheids and generally lacks vessels (Gnetum is an exception). Vessels are a characteristic feature of angiosperms.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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