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Answer.

Pollen grain is deposited on the stigma then pollen grain sticks to the surface of the stigma. The surface of the stigma produces a chemical substance which stimulates the pollen grain to produce a pollen tube/to germinate. The pollen tube grows through the style tissues on which it feeds until it enters the ovary.

The generative nucleus divides into two giving two male nuclei. Embryo sac contains eight nuclei i.e. two synergids, egg cell, two polar nuclei and three antipodal cells.

The pollen tube enters the embryo sac through the micropyle and one of the male nucleus fuses with the egg cell/ovum to form a zygote.

The other male nucleus fuses with the two polar nuclei to form the triploid nuclei/endosperm)food storage used by developing embryo). The pollen tube nucleus in the pollen tube disintergrates soon afterwards.

This process is referred to as double fertilization where zygote grows into an embryo containing plumule, radicle and cotyledons

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