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Meiosis in Flowering Plants
Plant Reproductive Structures
Plant Sperm production
Pollination and Fertilization
After landing on the stigma of a flower
(pollination), the tube cell elongates to
produce a pollen tube, which grows from
the stigma through the style and through the
micropyle to the egg. The generative cell will
divide by mitosis to produce two sperm. As in
gymnosperms, the sperm of angiosperms are
contained within the pollen tube and
therefore do not require water.
Fertilization
Fertilization
Double Fertilization: One sperm fertilizes the
egg the other one combines with the two polar
nuclei forming a triploid (3N) cell.
The zygote grows by mitosis to form an
embryo.
The 3N cell divides by mitosis and becomes
endosperm, a food-containing material for the
developing embryo.
The ovary, sometimes with other floral parts,
develops into a fruit. It usually contains seeds.
Summary
During pollination, the pollen grain sticks to the stigma.
Guided by the pollen tube nucleus , the pollen tube grows
through the micropyle near the base of the ovule.
The generative nucleus in the pollen grain divides by mitosis.
The two nuclei move into the embryo sac where one fertilizes
the polar nucleus to produce a triploid endosperm nucleus
and the other fertilizes the egg nucleus to form a zygote.