2. IB Bio HL II - Mrs Kate Ng Ch 9 Plant Science 9.1 Dicotyledonous plant structure 9.2 Transport in plants 9.3 Sexual reproduction in plants

4. Dicotyledonous vs monocotyledonous Plant

5. Phloem Stem Root Xylem Phloem Xylem Dicot: Vascular bundles in the Root

6. C. Structure of root Xylem Phloem Piliferous layer Cortex

7. A young dicotyledonous root

8. Phloem Xylem T.S. of root Piliferous layer Cortex Endodermis

9. Phloem Xylem Enlarged view of T.S. of root Endodermis Cortex

10. Types of root system There are 2 types of root system in the flowering plants: 1.Fibrous root system, and 2.Tap root system Each root has many root hairs close to its root tip. Root hairs are tiny hair-like projections of the epidermal cells of the root. They greatly increase the surface area of roots for absorption of water and minerals.

11. Fibrous root systemTap root system Fig.5 Root systems

12. Vascular bundles in the Stem Phloem Stem Root Xylem Phloem Xylem

13. D. Structure of stem Xylem Phloem epidermis Cambium Cortex pith Lateral meristems = cambium

14. Fig 9.4 Generalized young dicotyledonous stem (T.S.)

15. Phloem Xylem T.S. of Stem Vascular Bundle Pith

16. Phloem Xylem Enlarged view of T.S. of Stem, showing one vascular bundle Vascular Bundle Cambium Epidermis Cortex

17. Vascular bundles in the Leaf Phloem Stem Root Xylem Phloem Xylem

18. E. Structure of leaf Phloem Xylem Upper Side Under Side

19. Fig 7.5 (pg 112) Structure of a leaf

20. Lower epidermis Palisade mesophyll cells Spongy palisade cells Upper epidermis Air spaces Cuticle

21. Phloem Xylem T.S. of leaf, showing mid-rib & typical leaf regions

22. Phloem Xylem T.S. of leaf, showing typical leaf region Palisade mesophyll Upper epidermis Spongy mesophyll

23. Xerophytes Plants that live in dry environment Adaptations: Reduced spiky leaves Water storage tissues Grow near ground Flower and grow in the wet season and produce seeds before dry season Thicken waxy cuticle and lesser stomata

24. Modifications of leaf, stem and roots

25. 13.2 Transport in Flowering Plants There are 2 functions of the transport system: 1.Transport tissues Important for plants living on land because tissues in any region of plant are unlikely to have access to all the materials that they need from their environment. 2.Supporting tissues Large, land living plants may need additional support which transport tissues provide.

26. Transport Tissues The 2 transport (vascular) tissues of flowering plants are the xylem and phloem. Xylem transports water and dissolved materials. –Remember ‘Water in the XYlem – WXY’ Phloem transports food. –Remember ‘PHloem carries PHood’

27. Fig.1 Position of Xylem and Phloem in Plant

28. Xylem Xylem is made up of dead tissues consisting mainly of long, tube-like vessels with lignified walls. Lignified means that the cellulose cell walls have lignin added to them, this makes them hard and permeable to water. Gives support for the plant.

29. Xylem Characteristics: 1.They are long and narrow cells, 2.They are hollow and are without protoplasm (therefore dead cells), 3.The cells are joined end to end, without any cross walls and extend as continuous tubes from roots to stems and into the leaves, 4.The cellulose cell wall is strengthened by lignin.

30. Xylem The xylem tissues have 2 functions: 1.Conducting water, with its dissolved mineral salts, from the roots to the stems and leaves. 2.Providing mechanical support within the plant.

31. Xylem vessels showing the different patterns of lignification

32. Phloem Phloem is a living tissue consisting mainly of long sieve with cellulose walls. The function of the long sieve tubes is to transport food substances.

33. Phloem Characteristics: 1.They have cytoplasm but no nucleus. 2.The cells are joined end to end, and their end walls are perforated (known as sieve plates). 3.Strands of cytoplasm extend through the pores of sieve plates into the next cell.

34. Some components of phloem tissue

35. Transport of water The complete process of transpiration occurs in 3 distinct places: 1.Absorption by roots 2.Movement up the plant 3.Evaporation by the leaves.

36. 1. Absorption by roots –Roots are important for anchoring the plant in the soil, as well as for –Absorbing substances from the soil.

37. 1. Absorption by roots –The absorption of water is by osmosis, which is a passive process. –The cells of the roots contain relatively concentrated solution compared with water in the soil. –The result is a concentration gradient across the root, causing water to be drawn towards the central vascular bundle.

38. 1. Absorption by roots

39. –The absorption of mineral salts can occur by diffusion if the minerals involved are present in relatively small amount within the plants. –Active transport allows the plant to accumulate particular minerals above the concentration found in the surrounding soil; –The energy is derived from respiration.

40. 1. Absorption by roots –The relatively high concentration of minerals within the root tissues results in root pressure*, which probably helps push water up the plant.

41. 2. Movement up the plant –Water enters the open-ended xylem vessels in the central part of the root. –Xylem tissues form an almost continuous system of thin woody (lignified) tubes connecting the roots with the stem and leaves.

42. 2. Movement up the plant –There are 3 possible ways in which water is made to move up the plant: i.Root pressure ii.Capillary action iii.Transpiration pull (Cohesion Tension Theory)

43. i.Root Pressure –This arises from active transport into the root cells. –accounts for less than 25% of the force necessary to move water through the plant.

44. ii.Capillary action –What happens to the suction when the straw has a hole? –Apply to plants… –Results from water molecules “climbing” the narrow xylem vessels. –Adhesion occurs between the water and the lining of the xylem tubes. –These “pulls” water up the plant, although only for fairly short distant.

45. iii.Transpiration pull (Cohesion Tension Theory) –The cells inside the leaf are covered with a film of water. When this water evaporates into the air spaces in the leaf, it diffuses through the stomata into the surrounding air. –The loss of water from the mesophyll cells pulls in water from the neighbouring cells. –The tension or pull is created as the column water in the xylem vessels.

46. iii.Transpiration pull (Cohesion Tension Theory) –It extends all the way to the roots and pull water up to the top of the plant in a continuous column. –The flow of water is known as transpiration pull. –This account for most of the water movement up the plant.

48. 3. Evaporation by the leaves –Water evaporates from the surfaces of the mesophyll cells in the leaves. –The water vapour produced escapes to the exterior through specialised pores called stomata.

49. 3. Evaporation by the leaves –Water evaporates from the surfaces of the mesophyll cells in the leaves. –The water vapour produced escapes to the exterior through specialised pores called stomata. –Abscisic acid stimulates guard cells to close in response to water loss

50. Factors affecting the Rate of Transpiration Transpiration is dependent upon evaporation. Any factor that affects the rate of evaporation of water will affect the rate of transpiration.

51. External factors that influence the rate of transpiration are: 1.Humidity of the air –The more humid the air, the slower the rate of transpiration. 2.Temperature of the air –A rise in temperature of the surroundings increases the rate of evaporation, thus the rate of transpiration is greater.

52. External factors that influence the rate of transpiration are: 3.Strong wind –The stronger the wind, the higher the rate of transpiration. 4.Light –Light affects the size of stomata. Presence of light, transpiration rate increases. 5.Water availability Shortage of water will cause the closing of the stomata

53. IB Bio HL II - Ms Kate Loke 13.3 Sexual Reproduction in Flowering Plants Involves fusion of gametes Takes place in sex organs of flowers Involves pollination and fertilization Flower  Fruit  Seed  Reproduction of new plant

54. General Parts of a Flower

55. Parts of flowerFunction Sepals Petals Stamens – composed of a filament & anther Carpels – composed of ovary, style & stigma

56. Pollination Refers to the transfer of pollen from an anther to a stigma 2 types of pollination: – Self pollination – Cross pollination

57. Self-pollination Occurs when pollen from the anthers of a flower is transferred onto the stigma of the same flower or another flower on the same plant

58. Cross-pollination Occurs when the pollen from the anthers of a flower is transferred onto the stigma of another plant

59. Insect vs Wind pollination

60. Insect vs Wind-Pollinated flowers FeaturesInsect-pollinatedWind-pollinated PetalsLarge, conspicuous, bright coloured Small or absent NectarMay be presentAbsent ScentMay be presentAbsent AntherSmall, enclosed within flower Large, hanging outside flower

61. Insect vs Wind-Pollinated flowers FeaturesInsect-pollinatedWind-pollinated FilamentShort, rigidLong, flexible Pollen grains Sticky, rough & relatively large. Adhere to insect body Smooth, light & relatively small. Produced in large quantities, to offset losses. StigmaRelatively small, enclosed within flower Feathery, large S.A. exposed on outside of flower to collect pollen

62. Advantages of insects as pollinators Insects are carrier of pollen as they are: Small sized to enable them to gain entry into the flowers to obtain nectar. Highly mobile – many are winged or very industrious which enable them to visit a large number of flowers. Numerous in number. In a large variety of species.

64. Dispersal of Fruits & Seeds What are the advantages of dispersal methods? –Reduces the chances of inbreeding – Prevents overcrowding and competition for light and water with parent plant – Decrease vulnerability to epidemic attacks of diseases – Ensure variability –Enable plants to colonise new and favourable habitats

65. There are 4 types of dispersal methods: 1.Dispersal by wind 1.Dispersal by water 1.Dispersal by animals 1.Dispersal by self explosive mechanism Dispersal Methods

67. Seed vs Fruit How to tell from a seed and a fruit? A fruit has – One or more seeds, and –It has 2 scars : one where it was attached to the plant & one where the style and stigma were attached to A seed has – Only 1 scar where it was joined onto the fruit.

68. Structure of a seed

69. Structure of a typical seed FeatureFunctions Testa Hilum Micropyle Plumule Radicle

70. Structure of a typical seed FeatureFunctions Cotyledon

71. Seed Germination

72. Conditions required during germination External environmental conditions necessary for germination: Sufficient water –With water, cotyledons produce enzymes Suitable temperature –Required for enzyme activity Adequate oxygen supply –For respiration

73. Metabolic events in Germination What is Germination? –It is the onset of growth of the embryo. Changes during germination: 1.Seeds absorb water and swells, 2.Seed coat burst 3.Water activates gibberelline, a hormone needed for breaking the dormancy of the seed. 4.Gibberelline activates amylase whic to digest stored food into 5.Soluble products of digestion (glucose & amino acids) are transported to the growth regions of the embryos (i.e. plumule and radicle).

74. 4.Glucose is used for the synthesis of cellulose and other cell wall materials 5.Amino acids are used for protein synthesis as components of protoplasm 6.The dry mass decreases at first because of tissue respiration to provide energy for growth. 7.This loss will continue until the seedling produces green leaves and starts to photosynthesise and make its own food. Changes during Germination