Q.46 Which of the following genera produces dimorphic seeds that help to broaden the time of
germination in a variable habitat?
(A) Xanthium
(B) Pisum
(C) Mangifera
(D) Linum
Xanthium produces dimorphic seeds that enable staggered germination, enhancing survival in unpredictable environments. This adaptive trait distinguishes it from the other options in the multiple-choice question.
Correct Answer
The correct option is (A) Xanthium. This genus, commonly known as cocklebur, produces two distinct seed types within the same fruit: a large peripheral seed with quick germination and a small central seed with delayed dormancy. This dimorphism spreads germination over time, reducing risk in fluctuating habitats like disturbed soils or seasonal climates.
Option Explanations
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(A) Xanthium: Features dimorphic seeds promoting bet-hedging; large seeds germinate promptly under favorable conditions, while small ones remain dormant for later opportunities, ideal for variable habitats.
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(B) Pisum: Pea plants produce uniform, non-dimorphic seeds that germinate synchronously when conditions allow; no mechanism for staggered timing exists.
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(C) Mangifera: Mango seeds are single, large, recalcitrant types lacking dormancy variation; germination occurs rapidly post-ripening without dimorphism.
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(D) Linum: Flax seeds are small and uniform, germinating quickly under moist, cool conditions but without polymorphic traits for extended timing.
Biological Significance
Dimorphic seeds in Xanthium exemplify an evolutionary strategy for ecological resilience, as seen in Asteraceae weeds thriving in diverse ecosystems. This trait boosts seedling establishment amid unpredictability, unlike monomorphic seeds in the other genera.
Exam Preparation Tips
Focus on seed heteromorphism in weeds for botany MCQs. Compare with examples like Aethionema for broader context on bet-hedging in variable environments.
