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Sexual Reproduction in Flowering Plants. What are flowering plants?. -The flowering plants, also known as angiosperms are seed-producing plants.

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slide1

Sexual Reproduction in Flowering Plants

What are flowering plants?

-The flowering plants, also known as angiosperms are seed-producing plants.

-The characteristics of angiosperms includehaving flowers, endosperm within the seeds, and the production of fruits that contain the seeds.

Formation of male and female gametes in flowering plants

- Male and female gametes are produced in flowers

Gametes

Female

Male

Egg Cell (1)

Polar Nuclei (2)

Pollen Grain

slide2

Male and Female Structures in a Flower

Sticky

Join stigma to ovary

Carry Ovules

Place where pollen grains are produced

slide9

The Formation of embryo sac in the ovule

  • Ovary
  • is the part of the pistil which holds the ovule(s)
  • Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary
  • - A fruit is the ripened ovary or ovaries

Ovule

- The egg. A small structure in a seed plant that contains the embryo sac and develops into a seed after fertilization

slide10

Embryo Sac

  • A large cell that develops in the ovule of flowering plants.
  • It contains a large number of nuclei derived by division of the megaspore nucleus.
  • At the micropyle end is the egg nucleus and two synergids; at the opposite end are nuclei that will become the antipodals and in the centre are two polar nuclei which fuse to become the primary endosperm nucleus.
slide20

Review the formation of female gametes in a flower

E.S.M cell (2n)

3

1

Forms 4 (n) megaspores, 3 die

3 antipodal cells

2

2 synergid cells

1 egg cell

4

5

The nucleus of the functional megaspore

slide22

Pollination and the formation of pollen tube

Pollination

A process in which ripe pollen from an anther are transferred to a stigma

Fertlisation

Fertilisation starts when pollen grains land on stigma

Formation of pollen tube

The formation of pollen tube is stimulated by the sugar on the stigma. The pollen grain on the stigma will germinate and form pollen tube, grow into style towards ovule.

slide23

Sugar on stigma stimulates pollen grain to germinate

The pollen grain forms a tube known as ; POLLEN TUBE

The generative nucleus divide by mitosis forming 2 GAMETE NUCLEI

slide24

The pollen tube grows into the style towards the ovule

2 male gamete nuclei

The tube nucleus lead the 2 male gamete nuclei down the pollen tube

slide25

The pollen reaches the ovary

The pollen tube penetrates the ovule through the micropyle

Micropyle

slide26

The pollen tube penetrates the ovule through the micropyle

The tube nucleus disintegrates giving a clear passage for 2 male gamete nuclei

disintegrate

slide27

2 male nuclei

1 male nucleus

1 male nucleus

Fuse with egg cell

Fuse with 2 polar nuclei

+ 1 male nucleus

Diploid Zygote (2n)

Triploid Nucleus(3n)

+ 1 male nucleus

Embryo

Endosperm

slide28

The outer layer loses its moisture

*Protects the embryo and endosperm*

Ovule

seed

Embryo (2n)

*protects the seeds and may function to disperse them

Ovary develops

Fruit

Triploid Nucleus (3n)

*provides nourishment to the developing embryo*

*a nutrient-rich tissue

slide29

Fertilisation in Flowering Plants is called “Double Fertilisation”.

The process that takes place in ovule occurs twice

1st : The fertlisation of egg cell and 1 male gamete nucleus to form a diploid zygote

2nd : The fertlisation of 1 male gamete and 2 polar nuclei s to form a triploid nucleus

slide30

The importance of Double Fertilsation for the Survival of Flowering Plants

Give rise to endosperm

-Endosperm formed when 2 polar nuclei are fertilised

by 1 male gamete nucleus

-Endosperm is a nutritive cell, it stores food in form of

starch and protein as well as fat

-After a fertlisation in an ovule, there are 1 embryo and

1 triploid nucleus (which later develops into

endosperm). It means each embryo has its own

temporary food store in the endosperm

-Therefore, each embryo in each ovule feeds on its own

stored food in endosperm for survival

-Food stored in endosperm enable embryo lives longer

when the conditions are unfavourable