CSEC Plant Reproduction

CSEC Plant Reproduction

Flower Structure

• Petals – soft, modified leaves that surround the reproductive parts of the flower. 

• Sepal - encloses the flower bud and protects it before it blossoms. 

• •Receptacle - the structure at the top of the flower stalk. The receptacle supports the flower.

Flower Structure (male)

• Stamen - forms the male organs of the flower.

• Each stamen consists of a filament (stalk) which supports an anther.

• The anther produces the pollen grains (male gametes)

Flower Structure (female)

• Carpel - forms the female reproductive organs of the flower, consists of the stigma, style and ovary. 

• ­The stigma receives pollen grains during pollination.

• ­The style supports the stigma and holds it in a suitable position to receive the pollen.

Flower Structure (female)

• ­The ovary is the swollen, hollow base of the carpel and contains one or more ovules.

• ­Ovules - small structures that contain an egg cell (female gamete)

• The ovules will develop into seeds after fertilisation. 

Multiple Choice

The enlarged base of the pistil that stores the eggs of the plant is the ___.

• ovary
• ovule
• stigma
• style

Multiple Choice

The stalk that supports or holds up the anther is the

• style

• filament

• ovary

• pistil

Multiple Choice

They enclose the egg cells inside the ovaries.

• ovules
• anther
• seeds
• stamen

Multiple Choice

The tip of the style that has sticky hairs to trap pollen is the ___.

• stamen
• stigma
• ovary
• style

Pollination

• Pollination is the transfer of pollen from the stamen (male part of the flower) to a stigma (the female part of the flower).

• Pollen can be transferred from stamen to stigma by two main mechanisms:

• Wind pollination OR insect pollination

Wind pollination

• Wind blows the pollen off the stamen, and the pollen travels on the air currents until it lands on the stigma of plants of the same species.

Characteristics of Wind Pollinated Flowers

Insect Pollination

• Insects are attracted to the flower and are responsible for transporting the pollen from the stamen of one flower to the stigma of another

Insect pollinated flowers

• Petals are brightly coloured

• Produce small amounts of sticky pollen

• Sweetly scented and produce nectar to attract pollinators

• Stigmas are small and sticky

Multiple Choice

Wind-pollinated flowers usually have ______ and ________ petals. 

• big ... bright 
• small .... bright 
• big ... dull 
• small ... dull

Multiple Choice

Insect-pollinated flowers typically have

• Small, inconspicuous flowers

• No scent

• Light, powdery pollen grains

• Relatively large, and often sticky grains of pollen

Multiple Choice

I am a flower that produces nectar. What is the function of the nectar?

• To provide food for the flower
• To attract pollinators
• To attract animals to disperse the fruits
• To produce perfumes for Man

Multiple Choice

Wind-pollinated flowers typically have

• A scent

• Nectar

• Small, light and powdery pollen

• Large and colourful petals

Multiple Choice

Which structure is not essential in wind-pollinated flowers?

• anther
• ovary
• petal
• stigma

Self Pollination

• Self pollination: the transfer of pollen from the stamens to the stigma of the same flower, or to a flower on the same plant. 

• Self pollination reduces genetic diversity.

Cross pollination

• Cross pollination - the transfer of pollen from the stamens of one flower to the stigma of a different flower (of the same species) on a different plant.

• Cross pollination increases genetic diversity

Fertilisation

• For fertilisation to occur, the pollen grain must first land on the stigma of a compatible species. 

• The pollen grain then undergoes germination to form a pollen grain tube.

• The pollen grain tube grows down the style, towards the ovary.

Fertilisation

• The pollen tube will enter an ovule through the micropyle.

• The male gamete is transported in the pollen tube

• The male gamete then fuses with the female gamete in the ovule and fertilisation occurs.

• Fertilisation results in the formation of a zygote.

Multiple Choice

How does the male gamete reach the female gamate

• A pollen tube grows down the style

• A pollen grain moves down the style

• The male gamate digest its way down the style

• The male gamate swims down the style

Multiple Choice

What travels down the pollen tube?

• The whole pollen

• The pollen nucleus

• The whole ovule

• The ovule nucleus

Multiple Choice

What is fertilisation in plants?

• When the pollen nucleus fuses with the ovule nucleus

• When the ovary develops into a fruit

• When the sperm nucleus fuses with the egg

• When the pollen is taken to the stigma

Fruit Formation

• After fertilisation, the new zygote divides by mitosis to form the plant embryo

• The outer layers (integuments) of the ovule become hard and dry, forming the testa.

• The ovary wall develops into the fruit.

• The stigma, style and petals of the flower will fall off.

Fruit structure

• The fruit protects the growing seed.

• Pericarp: the wall of the fruit

• The pericarp has 3 layers: exocarp (outer layer), mesocarp (middle layer), endocarp (inner layer).

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Types of fruits

• Succulent (fleshy fruits) - layers of the pericarp are fleshy and juicy.

• Dry fruits - the pericarp is thin and dry.

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Seed Structure

• Testa - protects the seed from the external environment

• Plumule - embryonic shoot

• Radicle - embryonic root

• Cotyledons - the seed leaf, provides food for the growing seed,and is often the first leaves of the new plant.

Seed Dispersal

• Different plants rely on different methods of seed dispersal.

• Water dispersal: the seeds have air spaces which allow them to float on water. Eg: coconut.

• Mechanical dispersal - the seeds are ejected from the seed pod, scattering them away from the plant. Eg: ackee and red peas

Seed Dispersal

• Wind dispersal: seeds are light and can travel on air currents. Eg: pouii, dandelion

• Animal dispersal: seeds are surrounded by a fleshy fruit that is attractive to animals. The fruit is consumed by animals and the seeds are discarded or egested. Eg: mango

Multiple Choice

Which part of the seed is used for food storage?

• plumule

• radicle

• cotyledon

• testa

Multiple Choice

Name the part of the flower that develops into the seed

• The pollen grains

• The fertilised ovule

• The nucleus

• The ovary

Multiple Choice

What are the characteristic of the seeds dispersed by man and animals?

A: Can float on water

B: Sweet and juicy

C: Have hooks or stiff hairs

D: Have wing-like structures and are light

• A and B only

• B and C only

• C and D only

• A, B and C only

Multiple Choice

The purpose of seed dispersal is for the seeds to __________.

• germinate at the same time

• move to the same place and grow

• move further away from the parent plant

• compete with one another for minerals in the soil