Explain the events up to double fertilisation after the pollen tu

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 Multiple Choice QuestionsShort Answer Type

101.

Differentiate between:
Absortion Spectrum and Action Spectrum

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102.

Differentiate between:
Racemose and cymose inflorescence

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103.

A pollen grain in angiosperm at the time of dehiscence from an anther could be 2-celled or 3-celled. Explain. How are the cells placed within the pollen grain when shed at a 2-celled stage ?

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104.

(a) Can a plant flowering in Mumbai be pollinated by pollen grains of the same species growing in New Delhi ? Provide explanations to your answer.

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 Multiple Choice QuestionsLong Answer Type

105.

(a) When a seed of an orange is squeezed, many embryos, instead of one are observed. Explain how it is possible. 
(b) Are these embryos genetically similar or different ? Comment.

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 Multiple Choice QuestionsShort Answer Type

106.

Describe any two devices in a flowering plant which prevent both autogamy and geitonogamy.


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107.

Explain the events up to double fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm.


The events seen after the pollen tube enters one of the synergids in an ovule are as follows :

  1. Pollen tube, after reaching the ovary, enters the ovule through the micropyle and thus enters one of the synergids through filiform apparatus.
  2. After entering one of synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid.
  3. One of the male gametes move towads the egg cell and fuses with its nucleus thus result in the formation of the zygote (diploid cell). This is Syngamy.
  4. The other male gamete moves towards the two polar nuclei located in the central cell and fuses to form triploid primary endosperm nucleus (PEN). This involves fusion of three haploid nuclei & hence termed as triple fusion.
  5. Two types of fusions, syngamy & triple fusion take place in an embryosac and hence the phenomenon
    is termed as double fertilisation.
  6. After fertilisation, PEN becomes the primary endosperm cell (PEC) & develops into endosperm while zygote develops into an embryo.


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 Multiple Choice QuestionsMultiple Choice Questions

108.

Which one of the following statements is not true?

  • Exine of pollen grains is made up of sporopollenin

  • Pollen grains of many species cause severe allergies

  • Stored pollen in liquid nitrogen can be used in the crop breeding programmes

  • Stored pollen in liquid nitrogen can be used in the crop breeding programmes

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109.

In bryophytes and pteridophytes, transport of male gametes requires

  • insects

  • birds

  • water

  • water

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110.

Proximal end of the filament of stamen is attached to the

  • connective

  • placenta

  • thalamus

  • thalamus

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