B15.3 Sexual reproduction in plants

What is pollination?

• The transfer of pollen grains from an anther to a stigma

What is fertilisation?

• The fusion of the pollen and ovule nuclei to form a zygote

Identify insect-pollinated flower and its structures in diagrams

• Male part: stamen → produces pollen

• Female part: carpel → seeds develop in the carpel

Function of each structure

Structure	Description
Sepal	Protects unopened flower
Petals	Brightly coloured to attract insects
Anther	Produces and releases pollen grains (male gamete)
Filament	Supports the anther
Stigma	Top of female part which is sticky to trap pollen grains
Style	Supports stigma
Ovary	Contains ovules which will develop into seeds after fertilisation
Ovule	Produces and contains the ovum (female gamete) and develop into seeds after fertilisation

Adaptations of insect-pollinated flowers

Feature	Adaptation
Petals	Large and bright colors to attract insects
Stigma	Sticky so pollen grains stick to it
Anther	Inside flower to brush against insects
Scent and nectar	Entices insects to visit flower
No. of pollen grains	Moderate since insects transfer grains efficiently with a high chance of pollination
Pollen grains	Large, sticky and spiky to attach to insects so it can be carried away

Identify wind-pollinated flower and its structures in diagrams

Adaptations of wind-pollinated flowers

Feature	Adaptation
Petals	Small and dull
Stigma	Outside flower, feathery to catch drifting pollen grains
Anther	Dangles outside flower to catch wind-borne pollen
No scent or nectar	Has no need to attract insects
No. of pollen grains	Large amounts of pollen since it increases chances of successful pollination
Pollen grains	Smooth, small and light to be blown away easily

What is germination?

• Process controlled by enzymes in which the seed begins to develop into a new, young plant

What are the conditions required for germination?

1. Water: allows seed to swell up and enzymes in the seed to start working so seed can begin to grow

2. Oxygen: needed for aerobic respiration, which provides energy needed for growth

3. Temperature: since it is a process controlled by enzymes, there is an optimum temperature