PMR Form 3 Science Chapter 4 Plant Reproduction

1. Plant Reproduction

2. Reproduction of plants
Plants
Non-
Flowering
flowering
By Flowers & Vegetative Spores
Cones
Seeds reproduction formation

3. Plant Asexual Reproduction
• Above ground Stems arch over and take
root at the tips, forming new plants
(Forsythia, Raspberry and Strawberry)
• Horizontal above ground stems are called
stolons

4. Plant Asexual Reproduction
• Underground stems that serve for food
storage and reproduction. Rhizomes, bulbs,
corms and tubers

5. Plant Asexual Reproduction
• Leaves—Mitosis along the meristems at the
leaf margins produce tiny plantlets that fall off
and can take up an independent existence.

6. Advantages Of
Vegetative Propagation
• The young plant uses the food resources of the
parent plant, while it is developing.
• Only one parent plant is involved.
• Good and desirable parental characters are
retained in the offspring.
• The new plant formed matures more rapidly than
the plant which grows from seeds.
• A large number of desired varieties of plant are
produced in a very short time.

7. Disadvantages Of
Vegetative Propagation
• No new varieties are produced.
• Over crowding of the vegetative produced
plants leads to severe competition for survival
among them.
• Lack of variety leads to reduce resistance to
disease and changes in the environment.
• Colonization of the new localities is unlikely.
Thus the plants are not widely distributed.

9. The life cycle of a
flowering plant
4. Pollination
3. Flower
blossom
5. Fertilization
2. Plant
development &
maturation
6. Seed/Fruit
formation
1. Germination
7. Seed
dispersal

10. Seed Structure
Seed coat / Testa
Forms a tough Plumule
protective layer Embryo
shoot
Embryo –
grows into
seedlings
Cotyledon / Food store
Provides the embryo Radicle
plant with food. Embryo
root

11. Seed Germination

12. Plant grow & mature

13. The Parts of a Flower
• Most flowers have
four parts:
This is a bisexual plant!! – sepals,
– petals,
– stamen,
– carpels / pistil

14. Carpel
Stamen

15. Petals
Colourful to attract the insects pollinators

16. Sepals
Protect the flower bud
Carry out photosynthesis

17. Nectaries
give out sugary liquid to attract insects

18. Stamen
- Pollen grains
-Anther
- Filament

19. Pistils
- Stigma
- Style
- Ovary
- Ovule
• Receive
Style
• Protect ovule
pollen • Supports • Ovule becomes seed
grains stigma after fertilization
Stigma Ovary

21. Pollen
Pollen grains
Male gametes
Stigma
Pollen tube
Ovary
Ovule
Female gametes

22. Pollination
• Pollination involves the transfer of pollen (male
gamete) from the anther to the stigma (outermost
female part)

23. Types of pollination

24. Self pollination
No variation

25. Types of pollination
Cross – Pollination
– Pollen of a plant pollinates
another plant.
– Still genetically the same,
with variations

26. Advantages of Cross Pollination
Better Quality Fruits
Healthier Plants
Resistant to disease

27. Increase the chance of Cross-pollination

28. Plant pollinators - Animals

29. Plant pollinators - Wind

30. Unpollinated Pollinated
Flowers flowers

31. Insect Pollinated Plants

32. Some flowers provide food (e.g., nectar or pollen) to
their pollinators
Honey bee
collecting pollen
and nectar

33. Wind Pollinated Plants

34. Pollination Comparison
Structure Wind Insect
Pollinated Pollinated
Size Small Large
Petals dull bright colour
Scent none scented
Pollen light sticky
Stamen dangling outside inside flower
Stigma feathery sticky
Nectar none makes sugar

35. Pollen grain and Fertilisation

36. Formation of Pollen Tube

37. Pollination >>> Fertilization

38. After Fertilisation
Once fertilization has taken place the
zygote (fertilized ovule)becomes a seed,
and the ovary becomes a fruit.
The petals die and fall off.
The plant seeds are in the fruit.

39. Development of the seed and fruit
Ovule >>>> seed
Tissues of the ovary >>>> fruit

40. Development of the seed and fruit

41. Development of the seed and fruit
There are many kinds of fruits
Carpels
Flower
Stigma
Stamen
Ovule
Carpel
Each
(fruitlet) Stigma segment
develops
Seed
from the
carpel of
Stamen
one flower
Pea
Raspberry Pineapple
Simple fruit - single carpel of Aggregate fruit - many separate Multiple fruit - many carpels
one flower carpels of one flower of many flowers

42. What are fruits like?
The fruits can be:
- soft & fleshy
- hard & dry
• What fruits can you think of?
• What are their seeds like?

43. Soft & Fleshy Fruits

44. Hard & Dry Fruit

45. Seed Dispersal- why?
Seeds must be carried away (dispersed /
scattered) from the parent plant to:
• Reduce overcrowding
• Reduce competition for:
- Water
- Light
- Nutrients

47. How birds and animals help
seed dispersal
• Birds and animals
eat the fruits and
excrete the seeds
away from the
parent plant.

48. Development of the seed and fruit
Fruits aid seed dispersal
Many dry fruits are wind dispersed

49. Development of the seed and fruit
Fruits aid seed dispersal
Some dry fruits are animal dispersed

50. Development of the seed and fruit
Fruits aid seed dispersal
Many fleshy fruits are animal dispersed

51. Development of the seed and fruit
Fruits aid seed dispersal
Some fruits disperse seeds explosively
(e.g., some mistletoes)

52. Development of the seed and fruit
Fruits aid seed dispersal
Some fruits make seeds buoyant,
to aid dispersal by water

53. Seed Dispersal
Dispersal Description Seeds/
method Fruits
Wind Seeds are designed to
travel as far as
possible.
May have extensions
which act as
parachutes or wings.
Fruits may be shaken
like a pepper pot.

54. Seed Dispersal
Dispersal Description Seeds/
method Fruits
Animal Some have little hooks
(external) or sticky substances so
they stick onto the
animal’s fur, are
carried away and
rubbed off later.
Some carried away by
animals and dropped.

55. Types of Seeds

56. Dicotyledonous Seed

58. Stages of Seed Germination
Absorption of
Testa Radicle Grows
water through
Ruptures downwards
micropyle
Cotyledons is
Hypocotyl Lateral roots
pulled above
lengthens formed
ground
Plumule
Hypocotyl 1st foliage
exposed to
straighten leaves exposed
sunlight
Second leaves Photosynthesis

59. Seed Germination Process

60. Monocotyledonous Seed

61. Cotyledon
Hypogeal remains
underground
Types of seed
germination
Cotyledon above
Epigeal
the ground

62. Conditions for Seed Germination

66. GM Crops & Foods

68. Advantages of GM foods
(1) Pesticide alternative Crop loss due to pests can be financially crippling for farmers
which is the reason most farmers use pesticides. As an alternative to pesticides, crops
such as corn and soybeans can be genetically altered to resist pests - making the farmer,
the consumer and the environmentalist happy.
(2) Disease resistance There are many diseases - including fungi, viruses and bacteria -
that can attack crops. With new GM technology, scientists can create crops that are
genetically resistant to these attackers.
(3) Cold tolerance In order to prevent cold temperatures from killing crops, scientists can
take a gene that causes cold water fish to produce "antifreeze", and place it into certain
plants that are susceptible to frost.
(4) Drought resistance Genetically altering crops to resist drought and grow in otherwise
non-ideal conditions (like poor soil quality), farmers are able to grow crops in areas that
were previously unsuitable for agriculture.
(5) Adding nutritional value Scientists are able to identify nutritional deficiencies in
specific parts of the world, and genetically enhance the corn in order to satisfy the
nutritional need.