General
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UNIT 9:Plant reproduction
1. Look at the pictures below. What is going on in the pictures?
2. How can you help the family in picture B?
9.1 Definition and types of plant reproduction
Find out
1. What is plant reproduction ?
2. Two types of plant reproduction.
Activity 9.1 Investigating definition and types of
plant reproduction
1. Research in a library textbook or search engine what plant
reproduction is.
2. Obtain some healthy sugarcane cuttings.
3. Bury the sugarcane cuttings into the soil then observe for two
weeks.
Reproduction is the production of new plants from the parent plants
e.g cassava cuttings.
Reproduction occurs in two ways:
Asexual reproduction e.g sugar cane
Sexual production e.g beans
9.2 Identification of parts of a complete flower
Find out
1. Go out of the classroom and collect as many flowers as you can.
2. Observe the external parts carefully. What parts do you see?
3. Dissect the flowers and identify the internal parts.
4. Did all types of plants have the same type of flowers?
A Complete flower is made up of three main parts:
• The external flower parts
• The male reproductive parts
• The female reproductive parts
a) External parts of the flower
These include the stalk, calyx and corolla.
The flower stalk
The stalk joins the flower to the plant.
The calyx
This consists of small parts that look like leaves. They are called sepals.
Sepals protect the develping flower.
The corolla
Corolla consists of brightly coloured parts called petals. They attract
insects and birds thereby assisting during the pollination process.
b) Male reproductive parts
The male reproductive parts put together are know as stamen.
The stamen is made up of:
• Anthers - which contain pollen grains. Pollen grains are the
male reproductive cells.
• Filament - a long stalk that holds the anther.
c) Female reproductive parts
The female reproductive parts put together form the pistil
The pistil is made up of:
• Stigma - which receives pollen grains from the anthers during
pollination.
• Style - is a long and narrow tube that joins the stigma to the
ovary.
• Ovary - is the swollen part at the bottom of the style. It
contains ovules. Ovules are the female reproductive cells.
9.3 Process of sexual reproduction in flowering plants
Find out
1. Various agents of pollination.
2. How the agents cause pollination to occur.
Activity 9.3 I Investigating ways in which plant
reproduce
1. Research in search engine or library textbook on ways of plant
reproduction
2. Write down notes on various ways on which plants reproduces
Sexual Reproduction in flowering plants involves the following
processes : pollination, fertilisation, seed dispersal and seed germination.
a) Pollination
Pollination is the transfer of pollen grains from the anthers to stigma of
a flower.
There are two types of pollination:
• Self pollination - involves transfer of pollen grains from the
anthers to the stigma within the same flower or to the stigma of
another flower on the same plant.
• Cross pollination - This is the transfer of pollen grains from
the anther of one flower to the stigma of another flower on a
different plant but of the same type.
Agents of pollination
These refer to things that help to transfer pollen grains from the anther
to the stigma of another flower. They include:
Insects: example bees and butterflies
Birds: example: sunbird; wind, water.
• Birds and insects are attracted by bright colours and the sweet
scent of flowers. They help in the transfer of pollen grains. The
wind blows the pollen grains from flowers of one plant to the stigma
of flowers on another plant or within the same plant.
• Water flows downstream carrying pollen grains with it.
b)Fertilisation
• After pollination, fertilisation follows.
• When pollen grains reach the stigma, it germinates and grows
down through the style to the ovary and meets the ovules. This
process of joining together of the nuclei of pollen grains with that
of ovules is called fertilisation.
After fertilisation, the ovules become seeds and the ovary develops intoa fruit.
c) Seed dispersal
Seed dispersal is the scattering away of seeds in order to germinate and
grow into new plants.
Agents of seed dispersal
a) Self-dispersal
This is whereby fruits split open with a lot of force (explode) and
throw out the seeds.
b) Wind –Wind flows and spread the plant seeds at long distance
c) Animals
• Animals eat juicy and fleshy parts of fruits and scatter away
the seeds. Examples of such fruits are mangoes and oranges.
• Some fruits and seeds have hooks or spikes which stick to the
hair, fur or clothing of passing animals and human beings. They
later drop at distant places from where they grow into new
plants. An example is the black jack seed.
d) WaterFruits and seeds are dispersed by water.
d)Germination
Activity 9.4 Investigating germination of seeds
1. Plant some bean or maize seeds in a tin or box.
2. Water the planted seeds for one week as you observe what
happens
3. Discuss your findings.
Germination is the process by which a seed develops into a young plant
known as seedling. During germination, the following take place:
• The seed absorbs water through a tiny hole on the seed.
• The seed coat (testa) bursts and splits open.
• The radical comes out to form a tiny root.
• The plumule forms a shoot with tiny leaves and grows upwards.• The seedling grows to become a mature plant.
Self –Test 9.1
1. What is the function of a flower in a plant?
2. Draw and label the different parts of a flower.
3. _________ and __________ make up the stamen of a flower.
4. Name two seeds dispersed through wind and through water.
5. Many petals together form______while sepals form_______
6. What is pollination?7. Name two types of pollination
9.4 Asexual reproduction methods
Find out
Different types of asexual reproduction.
Activity 9.5 Investigating of types of plant asexualreproduction
1. Put the potato tuber into the soil and leave them for one week.
2. Observe the potato tubers such as the one alongside.
What can you see?
In asexual reproduction, there is no need of male or female sex cells
to come together. Here, a certain plant part may separate from the
parent plant and grow into a new plant. Asexual reproduction methods
include the following:
• Use of cuttings
• Grafting
• Layering• Use of suckers
a) Use of cuttings
Activity 9.6 Vegetative reproduction using
stem cuttings
1. Cut stems of sugarcane or cassava plant.
2. Plant the stems in the kitchen garden at home.3. Water them for five days then make your observations
We can use leaves, stem or root cuttings to come up with new plants.
e.g sweet potatoes, cassava, yams and sugarcane.
b) Grafting
Activity 9.7 Grafting1. Look at the picture below.
2. What is going on in the picture above?
The picture above shows the process of grafting.
In grafting, scion is added to the stem of another plant of same type
called the root. The two unite and come to grow together as one plant.
Examples of plants that can be grafted: oranges, lemons, mangoes,
avocados.Note: Grafting helps to improve the quality of a produce of certain plant.
Project work
1. Practise grafting using an orange plant (scion) with a lemon plant
(root stock) at home.
2. Take care of the plant until it produces fruits.
3. Taste the fruits produced. Are they different from the originalorange fruits?
c) Layering or marcotting
Activity 9.8 Layering
1. Bend one of the branches of a passion tree down as shown
below. Peg the branch into the soil and pile a heap of soil on the
branch.2. Leave it for one week and check if the roots have developed.
3. Cut off the branch from the main plant then plant it in a different
garden. Monitor the growth of the plant until fruiting.
4. Monitor the growth of the plant until fruiting.
Layering also known as marcotting. It is a form of asexual reproductionwhereby rooting is induced in part of a tree branch as shown above.
d) Suckers
Activity 9.9 Vegetative reproduction using suckers
1. Visit a banana or a sisal plantation.
2. Separate the plant lets from the main plant carefully. Plant it ina different place.
3. Water the plant let for a few days. Do they grow into mature
plants?
The small plants (plant lets) growing besides the mature banana or sisal
plants are called suckers. The suckers can be separated from their
parents and be planted at another location. The new plant continues togrow to become a healthy mature plant. eg: Pineapple, Ginger, Aloe Vera.
9.5. Reasons for plant reproduction
Find outThe reasons for plant reproduction.
Activity 9.10 Investigating the importance of plant
reproduction
1. Search in library textbook or search engine on plant reproduction.
2. Write down the reason for plant reproduction.
Reproduction in plants is important because it:
• Improves the quality of produce of crop plants.
• Prevent the plant species from becoming extinct.
• Helps to control plant diseases through mixing of genes.• Increases food production through research.
UNIT TEST 9
1. What is the difference between pollination and fertilisation?
2. The three agents of pollination are ___________, __________
and __________.
3. The ovules in a flower are produced in the _______________
while the pollen grains are produced in the ____________.
4. Distinguish between male and female parts of a flower using
diagrams.
5. Potato tuber is an underground __________. (stem, root)
6. After fertilisation __________ becomes seeds while __________
develops into a fruit.
7. Which method of reproduction would you recommend for the
following plants?
a) Banana ___________
b) Sugarcane ___________
8. Hagimana came across the following seeds during a field trip.The seeds are likely to be dispersed by ______________.
9. Distinguish between grafting and layering. Use diagrams.
10. Which conditions must be present for germination to occur?
11. Explain why bee-keeping is important near a sunflower farm.
12. Draw and label the parts of a flower.
13. Match each part of the flower in the table that follows with itsfunction using a line.
14. Give a reason why some plants have brightly coloured petals.
15. Why do most flowers have scent?