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EXTERNAL STRUCTURE OF FLOWERING PLANT

Objectives: By the end of this subtopic learners should be able to:
Identify the parts of a flowering plant. State the functions of each part of a flowering plant. Differentiate insect pollinated from wind pollinated flowers.

Flowering plants

Sunflower
Maize
Beans
Tomato

These plants produce flowers, fruits and seeds.

Characteristics of Flowering Plants

Seeds grow in fruits, nuts or pods.
Sexual reproduction.
Vascular system in leaves, stems and roots.

Maize Plant Plants

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Maize plant

PLANT	PART	FUNCTIONS
Maize
	Root	Holds the plant firmly. Carry water and minerals from the soil up the plant
	Stalk	Supports the plant, transports water and minerals throughout the plant
	Leaf	Produce food for plant through the process of photosynthesis.
	Tassel	Reproduction: produces pollen.
	Silk	Reproduction: it captures pollen from the tassel.
	Husk	Protects the maize seeds (fruit)
	Fruit	Bears seeds
	Seeds	Grows into a plant

Table 1 Parts of a maize plant and their functions

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Bean flower

External parts of a bean flower and its functions

Plant	Part	Function
Bean
	Stigma	Receives pollen grains from the anther.
	Style	Hold the stigma and a tube which connect the stigma to the ovary.
	Ovary	Produces ovules for fertilisation by anthers.
	Ovule	Used to fuse pollen grains to produce a zygote.
	Anthers	Produce pollen grains. (male part of the plant)
	Petals	Attract pollinators
	Sepals	Protect floral parts in the ovary.
	Receptacle	Attaches the flower to the stem.

Table 2 Parts of a bean flower and its functions

Pollination

It is the transfer of pollen grains from the anther to the stigma.
Pollen grains are immobile, they can not reach the stigma by themselves.
Pollen grains moved by external agents which include insects, water, gravity and growth contact.

Agents of pollination

Insects
Wind
Water

Self-pollination

Occurs when pollen grains from the anther of a flower to the stigma of either the same or genetically similar flower.
Self pollination maintains the parental characters or purity.

Cross pollination

Occurs when pollen grains lands on a different flower.

Comparisons between insect and wind pollinated flowers

Insect pollinated	Wind pollinated
Produces nectar to attract insects Have bright coloured petals to attract insect Anthers are inside petals Produce sticky pollen	No nectar Small and dull coloured petals Anthers are out of petals Pollen is not sticky

Table 3 Difference between insect and wind pollinated flowers

Summary:

Pollination is the transfer of pollen grains from the anther to the stigma.
Maize is wind pollinated
Bean is insect pollinated
Wind, insects and water are agents of pollination.