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Assertion :- Non synchronised pollen rel...

Assertion :- Non synchronised pollen release and stigma receptivity is of evolutionary significance.
Reason :- It prevent self pollination and promote more genetic variability

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A: continued self pollination checks inbreeding depression R: pollen release and stigma receptivity are synchornised

Assertion :- Development of pollen grains begins only after pollination. Reason : Development of pollen grain takes place only on stigma

Given below are five statements (i-v) regarding constrivances to ensure cross - pollination is plants (i) Dicliny - Anthers stigmas mature at different times in a bisexual flower. (ii) Dichogamy - Flowers are unisexual. (iii) Prepotency - Pollen grains of the same flower germinate more rapidly over the stigma than the pollen grains another flower. (iv) Heterostyly - Two or three types of flowers with different heights of styles. (v) Herkogamy - A mechanical device to prevent self - pollination which of the above statement are correct ?

Assertion : Self-incompatibility is a genetic mechanism which prevents self-pollination and thereby fertilisation by inhibiting either pollen germination or pollen tube growth in the pistil. Reason : In gametophytic self-incompatibility, the incompatibility reaction is determined by the genotype of the sporophytic tissue of the plant from which the pollen is derived.

Assertion. The time involved between pollination and fertilization varies from species to species Reason. All the pollen that reach the stigma succeed in affecting fertilization .

Assertion : Myelin sheath insulates the nerve fibre and prevents its depolarisation. Reason : Nerve impulses are conducted more rapidly in non-myelinated nerve fibres than in myelinated ones.

Assertion :Species with low genetic variability are generally at greater risk of extinction than the species with more genetic variability. Reason: Species with low genetic variability are more vulnerable to disease, predators or other environmental challenges.

Assertion : Although geitonogamy is functionally crosspollination involving a pollinating agent, genetically it is similar to autogamy. Reason : In geitonogamy, pollen grains from the anthers of one flower are transferred to the sigma of another flower borne on the same plant.

ALLEN-REPRODUCTION IN ORGANISMS AND SEXUAL REPRODUCTION IN FLOWERING PLANTS-EXERCISE-IV (Assertion & Reason )
  1. Assertion :- Cleistogamous flowers are invariably autogamous. Reason...

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  2. Asertion :- Cleistogamy is disadvantageous for plants. Reason:- Clei...

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  3. Assertion : Although geitonogamy is functionally crosspollination invo...

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  4. Assertion :- It is believed particularly for some bryophytes and pteri...

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  5. Assertion : Hydrophily constitues a major mode of pollination in most ...

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  6. Assertion :- Both wind and water pollinated flowers are not very colou...

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  7. Assertion :- Non synchronised pollen release and stigma receptivity is...

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  8. Assertion :- In monoecious plants neither autogamy nor geitonogamy can...

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  9. Assertion :- Most zygotes divide only after certain amount of endosper...

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  10. Assertion :- Seed bearing plants like angiosperms show wide geographic...

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  11. Assertion :- Apomixis is a form of asexual reproduction that mimics se...

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  12. Assertion :- Endosperm increases the success rate of seedling developm...

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  13. Assertion : Clone is formed by amphimixis. Reason : ln amphimixis, ne...

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  14. Assertion : Synergids of embryosac also help in fertilization in Angio...

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  15. Assertion : When embryo sac develops from megaspore mother cell withou...

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  16. Assertion : Pollen tube shows apical growth. Reason : Growth of polle...

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  17. Assertion :- Development of pollen grains begins only after pollinatio...

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  18. Assertion :- ln Angiosperms, sexual reproduction takes place through t...

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  19. Assertion :- The main plant of angiosperm is in the form of sporophyte...

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  20. Assertion :- Polygonum type of embryosac, is most common in angiosperm...

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