16.3 Sexual reproduction in plants

What is the function of the stigma?

It’s sticky surface catches pollen

What is the function of the style?

It links the stigma to the ovary

What’s the function of the ovary

It produced ovum(female sex cells)

What is the function of ovules?

It contains female sex cells

What is the function of the anther?

It contains pollen

What is the function of the filament?

It supports the anther

What is the function of the sepal?

It protects the unopened flower

What is the function of petals?

The bright colour of petals in insect-pollinated flowers attract insects

What is the male reproductive part of the plant called and what does it consist of?

Stamen

It consists of the anther and filament

What is the female part of the flower called and what does it consist of?

Carpel

It consists of the stigma, style and ovary

What is pollination?

The transfer of pollen grains from an anther to a stigma

What are the features of insect-pollinated flowers?

• Large and bright petals to attract insects

• Moderate amount of pollen as insects r more efficient in pollination

• Pollen grains are large, sticky and spiky to stick to insect body

• Scent and nectar present to attract insects

• Stigma is sticky and inside the flower

• Anther is inside the flower and firmly attached

What are the structural adaptations of a wind-pollinated flower?

• Petals are small and dull

• Pollen is present in large amount to increase chances of successful pollination

• Pollen grains are smooth, small and light so they can be blown easily by wind

• No scent nor nectar

• Stigma is feathery to catch drifting pollen grains and is outside the flower

• Anther is outside the flower, swinging loose to release pollen grains easily

What is self pollination?

The transfer of pollen grains from the anther of a flower to the stigma of the same flower, or a different flower on the same plant

What is cross pollination?

The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species

What are the effects of self pollination?

• Reduces genetic variation

• Limits the adaptability of offspring to changing environmental conditions

What are the effects of cross pollination?

• Increases genetic variation

• Relies on pollinators, can be a problem if they are missing

• Wind pollinated plants are not affected by the absence of pollinators

When does fertilisation in a plant happen?

When a pollen nucleus fuses with a nucleus in an ovule

Describe the process of fertilization in a plant

1. A pollen grain lands on the stigma

2. Pollen tube begins to grow down the style until it enters the ovule through the micropyle

3. The pollen nucleus moves down pollen tube

4. Pollen nucleus fuses with ovum nucleus to form a zygote

5. Ovule eventually develops into a seed

6. Ovary wall eventually develops into a fruit

Which factors are essential for seed germination?

• Water-causes seed to expand and activates enzymes within embryo to start growth

• Oxygen-for respiration to release energy for growth

• Suitable temperature-increases rate of germination, as enzyme-catalyzed reactions r temperature-dependent, up to an optimum

How to investigate germination?

Seeds don’t germinate in test tube A, due to lack of water

They germinate in test tube B as all factors are present

They don’t germinate in test tube C due to lack of oxygen

They don’t germinate in test tube D due to low temperature