1. Reproduction in Plants
Chapter 16
Reproduction in Plants

2. Objectives Students should be able to:
Define asexual reproduction as the process resulting in the production of genetically identical offspring from one parent
Define sexual reproduction as the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring

3. Identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a microscope
State the functions of the sepals, petals, anthers and carpels

4. Use a hand lens to identify and describe the anthers and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a microscope
Outline the process of pollination and distinguish between self-pollination and cross-pollination
Compare, using fresh specimens, an insect pollinated and a wind-pollinated flower

5. Describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (production of endosperm and details of development are NOT required)

6. 16.1 What is Reproduction? No organism lives forever
To ensure continuity of species, organisms must produce new organisms like themselves
 Production of new organisms is called reproduction

7. Two types of reproduction
Asexual reproduction
2. Sexual reproduction

8. Asexual Reproduction
Asexual Reproduction is process resulting in the production of genetically identical offspring from one parent, without the fusion of gametes
Gametes are reproductive cells containing half the chromosomes as the normal body cell

9. Asexual Reproduction Identical offspring produced Mitosis occurs.
A cell divides to give 2 identical daughter cells
Each daughter cells has the same no. of chromosomes as parent cell.
These daughter cells have identical genes as the parent cell. They are also called clones.

10. No. of chromosomes in cells varies with the species
Parent with 2n chromosomes 2n
Cell divides
(mitosis)
Two daughter cells formed, each with 2n chromosomes 2n 2n
No. of chromosomes in cells varies with
the species

11. Gametes are produced in a process known as meiosis
Sexual Reproduction
Is the process involving the fusion of two gametes to form a zygote, resulting in the production of genetically dissimilar offspring.
Gametes are produced in a process known as meiosis

12. In meiosis, A cell divides to form 4 daughter cells called gametes
Each gamete has half the number of chromosomes as the paent cell.
When gametes fuse during fertilisation, the normal number of chromosomes is restored.

13. Four gametes formed, each with
Parent cell with 2n chromosomes
nucleus
Cell divides (meiosis) 2n n
Four gametes formed, each with
n chromosomes

14. How are gametes involved in sexual reproduction?
The process of fusion of gametes is called fertilisation
The nuclei of the two gametes (male and female) fuse to form a zygote.
Zygote contains hereditary information from two different gametes, hence offspring produced is genetically different from both parents

15. 16.2 Sexual reproduction in Flowering Plants
New plants produced from seeds
Seeds are found in fruits
Each fruit is produced by a flower
Hence, flowers bear the reproductive organs of flowering plants

16. General Parts of a Flower
Pedicel
Is a flower stalk
Receptacle
Enlarged end of the flower stalk on which the other parts of the flower are borne

17. Sepals** Petals** Modified leaves
Function : enclose and protect the other parts of the flower in the bud stage
Sepals together forms calyx
Petals**
Modified leaves and forms the most obvious (conspicuous) part of the flower
insect-pollinated flowers, petals are
Brightly coloured to attract insects for pollination
Provide Landing platform for insects
Petals together form the corolla

18. carpel

19. Parts of a Flower
stigma
style
carpel
anther
ovary
stamen
ovule
filament
Sepal
Sepals are modified leaves which enclose and protect the other parts of the flower in the bud stage.
All the sepals together make up the calyx.
The sepals usually form the outermost layer of floral leaves.
However, some flowers, for example, Hibiscus, have another layer of floral leaves outside the sepals, which make up the epicalyx of the flower.
Figure 16.6 Page 298
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20. Parts of a Flower Receptacle
stigma
style
carpel
anther
ovary
stamen
ovule
filament
Sepal
Receptacle
The receptacle is the enlarged end of the flower stalk which bears the other parts of the flower.
Figure 16.6 Page 298
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21. Parts of a Flower Pedicel
stigma
style
carpel
anther
ovary
stamen
ovule
filament
Sepal
Receptacle
Figure 16.6 Page 298
Pedicel
The pedicel is the flower stalk. Some flowers have no pedicels and are attached to the plant directly at the base. They are called sessile flowers.
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22. Parts of a Flower
stigma
style
carpel
anther
ovary
stamen
ovule
filament
Petal
Petals are modified leaves forming the most obvious (conspicuous) part of the flower. All the petals together make up the corolla. In insect-pollinated flowers, petals:
are brightly coloured to attract insects for pollination; and
provide a platform for insects to land.
Sepal
Receptacle
Figure 16.6 Page 298
Pedicel
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23. Parts of a Flower stigma Petal style carpel ovary anther ovule stamen
filament
Figure 16.6 Page 298
Sepal
Receptacle
Pedicel
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24. Stamens** (Androecium)
Male part of the flower
Consists of a filament and an anther
All stamens together make up the androecium
Filament
Stalk that holds the anther
Anther contains a vascular bundle (xylem and phloem)
Anther**
Consists of two lobes
Each lobe contains two pollen sacs
Pollen sacs contain pollen grains

25. Parts of a Stamen It consists of an anther and a filament.
Side view of a stamen
Stamen
The male part of the flower.
It consists of an anther and a filament.
All the stamens together make up the androecium (plural: androecia).
Figure 16.8 pages
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26. Parts of a Stamen
vascular bundle
Stamen with upper half of anther cut off
Side view of a stamen
Stamen
Filament
The filament is the stalk that holds the anther in a suitable position to disperse the pollen. The anther also contains a vascular bundle. The vascular bundle contains:
phloem which translocates sucrose and amino acids to the developing anther. Sucrose provides the energy for cell division. Amino acids are used for synthesis of proteins and new protoplasm.
xylem which transports water and mineral salts to the anther.
Figure 16.8 pages
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27. Parts of a Stamen vascular bundle Anther
pollen sacs
pollen grains
anther lobes
Stamen with upper half of anther cut off
Side view of a stamen
Stamen
Filament
Anther
The anther consists of two lobes. Each lobe contains two pollen sacs. In the pollen sacs are the pollen grains. The anther produces pollen grains. When the anther matures, it splits open to release the pollen grains.
Figure 16.8 pages
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28. Parts of a Stamen Pollen grains
vascular bundle
pollen sacs
pollen tube nucleus
pollen grains
anther lobes
generative nucleus
Stamen with upper half of anther cut off
Side view of a stamen
Mature pollen grain
Pollen grains
Pollen grains contain the male gametes, which are produced by meiosis.
The nuclei in pollen grains contain the haploid number of chromosomes.
Each pollen grain has two nuclei, the generative nucleus and the pollen tube nucleus or vegetative nucleus.
Stamen
Filament
Anther
Figure 16.8 pages
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29. Carpel** (pistil or gynoecium)
Female part of the flower
Consists of:
an ovary,
a style above the ovary
and one or more stigmas
Stigma**
Receives pollen grains
Mature stigma secretes sugary fluid that stimulate the pollengrains to germinate

30. Parts of a Carpel Carpel The female part of the flower.
It consists of:
- an ovary;
a style above the ovary; and
one or more stigmas.
A flower may have one or more carpels.
All the carpels together make up the pistil or gynoecium (plural: gynoecia).
stigma
style
ovary
Figure 16.9 page 299
Side view of a carpel
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31. Parts of a Carpel Stigma
The stigma is a swollen structure at the end of the style.
It receives the pollen grains.
The mature stigma secretes a sugary fluid that stimulates the pollen grains to germinate.
style
Carpel
ovary
Figure 16.9 page 299
Side view of a carpel
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32. Parts of a Carpel
Style
The style is a stalk that connects the stigma to the ovary.
It holds the stigma in a suitable position to trap pollen grains.
Stigma
Carpel
ovary
Figure 16.9 page 299
Side view of a carpel
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33. Parts of a Carpel stigma Ovary The ovary contains one or more ovules.
Within each mature ovule is a female gamete or egg cell called the ovum (plural: ova) and the definitive nucleus. The ovum is produced by meiosis. It is therefore haploid.
The ovules are attached to a region in the ovary called the placenta. The ovule is attached to the placenta by a stalk called the funicle.
stigma
style
ovary wall
definitive nucleus
ovule
ovum
Figure 16.9 page 299
funicle
placenta
L.S. of a carpel
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34. Pollination
Pollen grains must be transferred from the anthers to the stigmas for the fusion of gametes
Can be done by insects or wind
Flowers pollinated by insects possess characteristics distinct from wind-pollinated flowers

35. What is Pollination?
The transfer of pollen grains from the anther to the stigma
If the pollen grains are transferred to a flower in another plant of the same kind, it is called cross-pollination

36. Self-pollination
Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or of a different flower of the same plant

38. Advantages Only one parent plant is required
Offspring inherits its genes from the parent plant. Hence good qualities passed down to the offspring
High probability of pollination
Less pollen grain and energy wasted in self-pollination

39. Disadvantages
Less varieties are produced. Hence species is less adapted to environmental changes
Continued self-pollination may lead to offspring becoming weaker, smaller and less resistant to diseases

40. Cross-pollination
Cross-pollination is the transfer of pollen grains from one plant to the stigma of a flower in another plant of the same species

42. Advantages of cross-pollination
Offspring may have inherited good qualities from both parents
More varieties produced. This increases the chance of species surviving environmental changes
More viable seeds are produced

43. Disadvantages of cross-pollination
Both parents required
Depends on external factors such as insects or wind for pollination
Lower probability of cross-pollination
More energy and pollen grains wasted

44. Self Pollination vs Cross Pollination
Self Pollination results in the production of
offspring that are weaker and
less adaptable to changes in he environment
Cross Pollination may produce
Offspring with valuable qualities
Abundant and more viable seeds
More varieties of offspring

45. The Structure and Pollination of an Insect-Pollinated Flower
Structure of Clitoria flower
Belongs to the legume (pea) family

46. External features of Clitoria
Figure Page 303
The Clitoria flower is pollinated by insects. The flower is complete, bisexual and bilaterally symmetrical.
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47. External features of Clitoria
pedicel
calyx
Figure Page 303
The calyx consists of five green sepals. 1
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48. External features of Clitoria
pedicel
epicalyx
calyx
Figure Page 303
The base of the calyx is enclosed by the epicalyx. The epicalyx consists of two green leaves. 2
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49. External features of Clitoria
pedicel
epicalyx
calyx
corolla
Figure Page 303
The corolla consists of five brightly-coloured petals
of different shapes and sizes. 3
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50. External features of Clitoria
pedicel
epicalyx
calyx
corolla
standard petal
standard petal
Figure Page 303
The large, deep blue standard petal has lines on it that guide insects to where the nectar is located. 4
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51. External features of Clitoria
pedicel
epicalyx
calyx
corolla
nectar guide
standard petal
standard petal
Figure Page 303 4
The large, deep blue standard petal has lines on it that guide insects to where the nectar is located.
Thus, these lines are called nectar guides.
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52. External features of Clitoria
pedicel
epicalyx
wing petal
calyx
wing petals
corolla
nectar guide
standard petal
standard petal
Figure Page 303
Two deep blue wing petals are enclosed by the standard petal. 5
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53. External features of Clitoria
keel petals
pedicel
epicalyx
wing petal
calyx
wing petals
corolla
nectar guide
standard petal
standard petal
Figure Page 303 6
Two small, yellowish-green keel petals are enclosed by the wing petals. The keel petals enclose the reproductive organs.
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54. Stamens and Pistil of Clitoria
Androecium
The androecium consists of ten stamens with long filaments.
The filaments of nine of the stamens are fused along most of their length to form a hollow tube or ‘trough’. This trough encloses the pistil.
Nectar, secreted by the flower, collects at the bottom of the stamen trough. Thus, the nectar can be reached only by an insect with a long tubular mouth or proboscis, for example, a bee or a butterfly.
stamen trough
Figure Page 304
Stigma and stamens of Clitoria
stigma
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55. Stamens and Pistil of Clitoria
Androecium
The androecium consists of ten stamens with long filaments.
The filaments of nine of the stamens are fused along most of their length to form a hollow tube or ‘trough’. This trough encloses the pistil.
Nectar, secreted by the flower, collects at the bottom of the stamen trough. Thus, the nectar can be reached only by an insect with a long tubular mouth or proboscis, for example, a bee or a butterfly.
stamen trough
Figure Page 304
Stigma and stamens of Clitoria
The tenth stamen is free.
stigma
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56. Stamens and Pistil of Clitoria
The pistil consists of a single carpel.
Section of the carpel of Clitoria
Figure Page 304
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