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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The filiform apparatus, which guides the pollen tube into the embryo sac, is present in the:
सही उत्तर: क) Synergids
Synergids have cellular thickenings at the micropylar tip called the filiform apparatus. Antipodals lie at the chalazal end.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A typical (Polygonum type) embryo sac of angiosperms at maturity is:
सही उत्तर: क) 7-celled and 8-nucleate
It has three antipodals, two synergids, one egg and one central cell containing two polar nuclei: 7 cells, 8 nuclei. The central cell is binucleate, so cell number is less than nucleus number.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The outer layer (exine) of the pollen grain is made of:
सही उत्तर: ग) Sporopollenin
Sporopollenin is extremely resistant to high temperature, acids and enzymes, which is why pollen fossils are preserved. The inner intine is made of cellulose and pectin.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The photoreceptor pigment involved in photoperiodism, existing in red and far-red absorbing forms, is:
सही उत्तर: घ) Phytochrome
Phytochrome exists as Pr and Pfr forms that interconvert with red and far-red light. Cytochromes are electron carriers in respiration, not photoreceptors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Promotion of flowering by exposure to low temperature is called:
सही उत्तर: घ) Vernalisation
Vernalisation is the low-temperature treatment that induces or hastens flowering, as in winter wheat. Photoperiodism is the response to day length.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The 'foolish seedling' (bakanae) disease of rice led to the discovery of:
सही उत्तर: घ) Gibberellins
Kurosawa found that the fungus Gibberella fujikuroi caused excessive elongation of rice seedlings, leading to the discovery of gibberellins. Cytokinins were discovered as kinetin from autoclaved herring sperm DNA.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which plant hormone is a gas and promotes ripening of fruits?
सही उत्तर: क) Ethylene
Ethylene is a gaseous hormone that hastens fruit ripening and is used for ripening bananas commercially. The other three are non-gaseous hormones.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The 'stress hormone' that causes stomatal closure is:
सही उत्तर: ग) Abscisic acid
Abscisic acid (ABA) increases under water stress and closes stomata; it also induces seed dormancy. Gibberellins break dormancy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The plant hormone that delays leaf senescence (Richmond–Lang effect) is:
सही उत्तर: घ) Cytokinin
Cytokinins delay senescence by promoting nutrient mobilisation. Ethylene and abscisic acid promote senescence.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Apical dominance in plants is caused by:
सही उत्तर: ख) Auxin
Auxin produced by the shoot apex suppresses the growth of lateral buds. Cytokinins tend to overcome apical dominance and promote lateral bud growth.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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