Sexual reproduction in plants ppt

Overview of floral organs

Structure of the flower• It is the organ for sexual reproduction• It has sepals petals , stamens & carpels • Stamens & carpels are the reproductive parts of

the flower which contain the germ cells Carpel/

Flowers are of two types

1. Unisexual flowers

2. Bisexual flowers

Unisexual flowers

Flower which contains either stamen or pistil is called unisexual flower

Ex-papaya , water melon

Flower which contains both stamen & pistil is called Bisexual flower

EX- Hibiscus , Mustard

Reproductive floral organs: female• Carpel or pistil – female

reproductive organ• Itcontains:• Ovary – enlarged structure

at the base of carpel/pistil where the ovules are located; it will become the fruit after fertilization

• Ovules – contains female germ cell or egg cell.

• It becomes seed after fertilization

• Stigma – is where pollen sticks to

• Style – is the long tube that connects stigma to ovary

carpel or pistil

ovary

Reproductive floral organs: male• Stamen – male floral organ • It consists of:• Anther – part of the stamen that produces pollen• Filament – stalk-like structure that holds anther• Pollen grain –male gametophyte which consist

of male gametes

Steps in sexual reproduction• 1. Pollination• 2. Germination of pollen grain• 3. Fertilization • 4. Formation of the fruit & seed

POLLINATION• The transfer of

pollen from the male anther to the female stigma

NEED FOR POLLINATION• The male gamete

present in the pollen grain fuses with the egg cell present in the ovule to form the zygote which produces a new plant

• For this the pollen needs to be transferred from stamen to the stigma

Types of pollination• 1. Self pollination• 2. Cross pollination

Transfer of pollen grains from anther to the stigma of the same flower is called self pollination

Transfer of pollen grains from anther to the stigma of the another flower is called cross pollination

Pollen grain germination• After the pollen lands on

the suitable stigma, it has to reach the female gamete present in the in the ovary

• For this pollen grain germinates on the stigma & forms a pollen tube

• It travels through the style & reaches the ovule present in the ovary

Fusion of the male & female gametes is called fertilization

It occurs inside the ovule

Pollen grain germination & fertilization

FORMATION OF THE FRUIT & SEED

• After fertilization the zygote devides several times to form an embryo within the ovule

• The ovule develops a tough coat & is gradually converted into a seed

• The ovary grows rapidly to form a fruit• Sepals , petals, stigma, style fall down

Double Fertilization• Double fertilization occurs: One sperm

nucleus (1n) fertilizes the egg, producing a zygote (2n) which becomes the plant embryo inside the seed

• Another sperm nucleus fuses with the polar nuclei, resulting in a triploid endosperm (3n)

• Endosperm is a source of food for the young embryo.

Endosperm

Structure of the seed

•It has cotyledons

•Plumle- which gives shoot system

•Radicle which gives root system

Seed germination• The seed

contains the future plant or embryo which develops into seedling under appropriate conditions. This process is called seed germination