Sexual Reproduction in Plants

2

• That involves the reproductive structures:– Flowers and Fruits

• 2 parents are involved.• Fusion of male and female gametes• Male gametes:

– pollen grains

• Female gametes:– ovules

• Where are these gametes found?– flowers

SEXUAL REPRODUCTION IN PLANTS

PETAL

STAMEN

PISTILMale Part

Female Part

Mrs Theresa Teo GE2003

Parts of a Flower

pistil/

pedicel

ovules?

Function of different parts of the flower

• The stamens are the male parts of the flower. They consist of filaments which is like a stalk supporting the pollen-producing anther.

• The pistil is the female organ of the flower. It is made up of one or more units called carpels. Each carpel usually consists of an ovary, a style above the ovary and a stigma. The stigma is the swollen structure at the end of the style that receives the pollen grains. The ovary contains one or more ovules which contains the female gamete.

Function of different parts of the flower• The pedicel is a flower stalk.• The receptacle is the swollen part of the flower

stalk which holds all the other parts of the flower.• The sepals are modified leaves which enclose

and protect the other parts of the flower in the bud stage.

• The petals are modified leaves usually forming the conspicuous part of the flower and they usually have nectaries at the base which hold nectar.

Petals are brightly colored structures used to attract

insects by their bright color & scent.

Anther

FilamentPollen Grains

Stigma

Style

Ovary

One or more carpels make up the pistil , which is the female part of the flower.

Pollen Grain

Sticky Stigma

Style

Ovary

Ovules

Within each ovule is a microscopic female gamete (female reproductive cell)!!!

Stamen: Male part of the flower; consists of 2 parts – filament & anther.Anther: Sac-like container within which pollen grains develop.Filament: Slender stalk that supports the anther.Pollen/Pollen grains: Contains the male gametes (reproductive cells) for plants.

Carpel: Female part of the flower; consists of 3 parts – stigma, style & ovary.Stigma: Enlarged sticky knob on the end of a style; serves to receive pollen grains.Style: Slender stalk that connects stigma to ovary.Ovary: Enlarged base of the carpel that contains a number of ovules.Ovules: Contains the female gametes (reproductive cells) also called the egg or ovum for plants.

What we have just seen is a bisexual flower, where both the male & female parts are found

on a single flower.However, there are unisexual

flowers present too, where the male & female parts are found

on separate flowers.

Examples of unisexual flowers are:

Maize, papaya & cucumber

Male Papaya Flower Female Papaya Flower

Stamen

Carpel

StamenCarpelFruit

Male Cucumber Flower Female Cucumber Flower

Now, lets have some fun with group work!In groups of 5, label the flower parts and deduce whether the

flower is male or female…

Now that we know more about flowers and flower parts, what do

you think happens when a bee lands on a flower to obtain nectar???

I want two volunteers to come up, one with a male flower, one with a female

flower…Let us observe what happens

when the bee lands on the flower…

Can anyone tell me what you did you

observe happen when the bee lands on the

flower?

Pollination takes place. Let’s take a look at how it

happens…

When the anther is mature, it splits open and the pollen grains

are released from its sac!!!

OH!!! You mean like

this…

Pollen

These pollen grains are small and light.When the bee lands on the flower, it will push through the anthers to get its nectar. When that happens, its body will rub against the pollen and some of it will get stuck on its body. On its way out, the pollen that’s on its body will get stuck on the sticky stigma.

When this (pollen landing on stigma) happens, pollination

takes place.If pollen from the anther lands

on the stigma of the same plant, self-pollination occurs.

If the pollen from the anther lands on the stigma of another flower, then cross-

pollination occurs. This can be different flowers of the same plant of different flowers of different plants of the same

species.

can occur in 2 main ways…

By Animals By Wind

What differences do you observe in these 2 flowers?

Homer, what happens after pollination, when the pollen

has landed onto the stigma???

Bart, fertilisation will take place in plants, just like in humans. But it will

go through a different process instead…

Let’s find out what really happens…

Micropyle

Pollen Tube

Ovary

Grows as it isattracted by sugar in the

stigma.

Ovule

Diagram of Ovule

When the pollen tube reaches the ovule, the tip of the pollen tube breaks open to release a nucleus which fuses with the nucleus of the

egg cell. Fertilisation has taken place.

Fusion

Fertilized egg forms a zygote.

Zygote develops into an embryo in

the ovule.

Releasesnucleus

Ovary develops into a fruit

Ovule/Ovulesdevelop intoa seed/seeds.

Papaya

We can see that theflower has been

replaced by a fruit!

Flower turning into a fruit Fruit

Wow… so that’s how

seeds & fruits are formed…

Ovary becomes

fruit

Ovules become

seeds

Fruit carries & protects seeds until they are releasedwhen the fruit is ripe.

Now, seeds can be replanted to become plants again before

bearing flowers, then turning into fruits as the

cycle repeats itself…

In the sexual reproduction in animals & plants…

1. Both plants & animals have a male reproductive cell, called sperm in animals & a pollen grain in plants.

2. Both plants & animals have a female reproductive cell, called a ovum in animals & a ovule in plants.

3. In both animals and flowering plants, a new organism is formed when the male reproductive cell and the female reproductive cell fuse.

We eatbroccoli, cauliflower

& artichoke

Cloves, saffron, rosepetals & marigold petals

are used to add flavour to the food.

Dandelion&

elder-berry

flowersare

used tomakewine.

Clover, orange &sage flowers is best for honey-

making.

Flower petals ofjasmine, mimosa& rose are used

to make expensive perfumes.

Petals of somebrightly colored

flowers are used to make colored dyes for clothes.

FlowerBisexual/Unisexual

Male Part:Pollen grains in anther

Female Part:Ovules in carpel

Pollination (Self & Cross)

Insect-Pollination

Wind-Pollination

Fertilisation(Fusion of pollen & egg cell in ovule)

Development of fruits & seeds

1. Understand that plants reproduce to ensure continuity of their kind.

2. Label the different parts of the flower.

3. List the respective functions of the different parts of the flower.

4. Know what is a bisexual & unisexual flower (& some examples).

5. Know the process of pollination (can occur in 2 main ways) & the features of insect & wind-pollinated flowers.

6. Know the process of fertilisation (how seeds & fruits are formed).

7. Know the similarities in the sexual reproduction in plants & animals.