Question

Explain the events up to double fertilisation after the pollen tube enters

Answer 1

aloha user!!

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ミ after pollen grains get attached to stigma 
they form pollen tube.

ミ two male gametes move from this tube 
to the ovary.

ミ one male gamete fertilizes the ova or egg (forming
diploid zygote).

ミone male gamete fuses with two polar nuclei(forming
triploid endosperm nucleus).

ミafter fetilization,

☆ the ova turns into seed.
☆ the ovary turns into fruit.

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hope it helps :^)

Answer 2

• After fertilisation the male gamets move down to the ovule forming a tube .

• This tube is formed due to the Chemotropism.

A sugary substance produce by carpel act as a stimulus for the pollen grains which fall on the stigma of the carpel.

• Since a pollen grains contain two male gametes , one male gamete fusses to the female gamete to form Diploid Zygote. It is called as generative fertilisation.

Another male gamete fusses with the two polar nuclei to form Triploid Endosperm and called as triple fussion.
It is Vegetative fertilisation.

Hence , in the ovule fertilisation occur two times i.e, called Double fertilisation.

• After the double fertilisation , the endosperm develop to form seed cotyledon which cover Zygote while the ovary develop to form Fruits.