1. Plant Structure and Growth
Chapter 35
Plant Structure and Growth

2. Chapter focus Plant structure and growth
Warning – many terms or vocabulary words
Warning – many diagrams
Focus – structure, function, located next to ….

3. Question ?
What heading can be given to the following groups of words?

4.
Lettuce
Peas
Beans
Rhubarb
Apples
Oranges

5. Question ?
What is a vegetable?
What is a fruit?

6. Vegetables
Lettuce
Rhubarb
Fruits
Peas
Beans
Apples
Oranges

7. Point Plants have organs too, just like animals.
Asexual organs (vegetables)
Sexual organs (fruits)

8. Asexual Organs
1. Stem
2. Leaf
3. Root

9. Stem
The main body of the portion above ground of a tree, shrub or herb.
The ascending plant axis.

10. Stem Functions Support of other plant organs. Ps.
Storage (water and food).

11. Leaf Lateral outgrowths of the stem axis.
Primary photosynthetic organs.
Function:
Photosynthesis
Storage

12. Root The descending axis of a plant, normally below ground. Functions:
Anchorage.
Absorption of water and minerals.
Storage.

13. Sexual Organs
1. Flowers
2. Fruits
3. Seeds

14. Flowers Modified leaves grouped together on a stem.
Sexual reproductive organs.
Function:
Sexual Reproduction

15. Fruit A mature ovary, sometimes including other floral parts.
Function:
Seed dispersal
Seed protection

16. Seed Mature ovule containing the embryo and nutrient tissues.
Function:
Dispersal unit in sexual reproduction.

17. Plant Cell Types
Differentiated by the type and thickness of the cell wall.
1. Parenchyma (soft tissue)
2. Collenchyma (glue tissue)
3. Sclerenchyma (hard tissue)

18. Parenchyma Cells Primary wall only. Thin cell wall. Alive when mature,
“typical" plant cell.

19. Functions Ps
Storage
"Filler" cells
Cell division (mitosis)

20. Collenchyma Primary wall only.
Wall is thickened, especially in the corners.
Alive when mature.

21. Function
Support of non-woody plant parts.
Ex: veins, stems.

22. Sclerenchyma Secondary wall present. Wall strengthened with lignin.
Dead when mature.

23. Sclerenchyma Types 1. Fibers 2. Sclereids 3. Tracheids
4. Vessel Elements

24. Fibers
Elongated thin cells used for support.
Ex: Hemp fibers

25. Sclereids Used for hard dense areas and support.
Ex: Nut shells, seed coats

26. Tracheids Spindle - shaped cells with pits in the cell walls.
Used for water transportation.
Vessel
Fiber

27. Vessel Elements
Wide stocky cells with pits in the side walls; lack end walls.
Used for water transportation.

28. Plant Tissues Can be named by several methods:
Ex: Cell Location Cell Origin Cell Function

29. Point
The same cell can have several tissue names depending on the criteria for naming.

30. Main Tissue Systems
1. Dermal
2. Vascular
3. Ground

31. Dermal Tissue Epidermis or "skin" of the plant.
Often has a cuticle, a waxy coating to prevent water loss.
Functions:
Prevent water loss.
Water absorption (root hairs).

32. Vascular Tissue Made of Xylem and Phloem. Functions:
Transport and support
Xylem - Water
Phloem - Food

33. Xylem

34. Phloem

35. Phloem Sieve Cell – alive when functioning, but lacks a nucleus.
Companion Cell – alive, controls itself and the sieve cell.

36. Ground Tissue Tissue between the dermal and the vascular tissues.
Functions:
"Filler" tissue Ps
storage
support

37. Question ?
How does plant growth and animal growth differ ?

38. Animals Whole organism increases in size.
Determinant Growth: grow to a certain size, then stop.

39. Plants Growth in specialized areas only.
Indeterminant Growth: grow as long as they live because the specialized areas remain embryonic.

40. Plant Meristems
Perpetual embryonic regions.
Zones for cell division.

41. Meristem Types 1. Apical growth in length. Primary growth.
2. Lateral/Cambiums growth in diameter. Secondary growth.

42. Comment
Some tissues like Xylem may be Primary or Secondary depending on which meristem produced the cell.
Ex:
Primary xylem
Secondary xylem

43. Apical Meristem Types
1. RAM – Root Apical Meristem: primary growth of roots.
2. SAM – Shoot Apical Meristem: primary growth of shoots.

44. RAM Located at the tip of each growing root.
Protected from the soil by the Root Cap.
RAM

45. Root Cap
Protects RAM.
Secrets a polysaccharide lubricant for root growth.

46. Primary Root Zones 1. Cell Division - cells small and embryonic.
2. Cell Elongation - cells elongate and start to mature.
3. Cell Differentiation - cells mature into final cell types.

48. Root Hairs
Extensions of the epidermis to increase surface area for water absorption.
Not a true tissue.
Comment - root hairs are very delicate and must be continually replaced.

49. Root Hairs

50. RAM - Primary Tissues
1. Protoderm
2. Procambium
3. Ground Meristem

51. Protoderm
Will mature into the epidermis and root hairs.

52. Procambium Stele Matures into the vascular tissues of the stele: Xylem
Phloem
Pericycle – site of branch roots

53. Ground Meristem Matures into the ground tissues:
Cortex – storage tissue
Endodermis – second skin around the stele that controls the movement of materials into the stele.

54. Epidermis
Cortex
Stele

55. Endodermis
Pericycle
Xylem
Phloem

56. Branch Roots Originate from the pericycle.
Burst their way to the outside.

57. Root Types Taproot - one main root.
Ex: carrot
Fibrous Roots - many small roots of equal size.
Ex: grass roots

58. Adventitious Roots Roots that develop from other plant parts.
Ex: roots on stem cuttings climbing roots

59. SAM Produces 1. Protoderm 2. Procambium 3. Ground Meristem
Comment – these tissues mature into the same things as seen in RAM.

60. SAM Differences No "root" cap.
Produces leaves as stem out-growths at the nodes.
Has buds.

62. Buds Apical Meristems protected by modified leaves or bud scales.
Axillary Buds

63. Branch Stems Develop from axillary meristems or axillary buds.
"External" development.

64. Modified Stems
1. Rhizomes
2. Stolons
3. Tubers
4. Tendrils

65. Rhizome An elongated underground horizontal stem.
Ex: Iris, many grasses

66. Stolon An elongated above-ground horizontal stem.
Ex: Strawberries Airplane Plant

67. Tuber A much-enlarged, short, fleshy underground stem tip.
Ex: Dahlia, Potato

68. Tendril
A slender coiling stem.
Ex: Clematis and other climbing vines.

69. Leaves
Stem outgrowths for Ps.
Leaf Morphology:
1. Gross
2. Fine

70. Gross Morphology Blade - the flattened portion of a leaf.
Petiole - stalk of a leaf.

71. Axillary Buds
Blade
Petiole

72. Blade/Leaf Types
Simple - 1 blade.
Compound - Several blades.

73. Nodes and Internodes
Node - stem area where a leaf and bud are attached.
Internode - stem area between nodes.

74. Nodes }
Internode

75. Fine Morphology The tissues within a leaf. 1. Upper Epidermis
2. Mesophyll
3. Lower Epidermis
4. Veins

76. Upper Epidermis Cuticle present. Usually 1 cell layer thick.
Cells w/o chloroplasts .
Function: protects the mesophyll.

77. Mesophyll 1. Palisade upright cells.
2. Spongy loosely organized cells with air spaces.
Function: major sites for Ps.
Epidermis
Epidermis

78. Lower Epidermis Cuticle present. Usually 1 cell layer.
Cells w/o chloroplasts.
Stomata present for gas exchange.

79. Stomata (mouth)
Regulated by Guard Cells which have chloroplasts.

81. Vein Structure Xylem: dorsal Phloem: ventral
Often surrounded by bundle sheath cells for support.

82. Xylem
Phloem
Bundle Sheath Cells
Collenchyma

83. Homework Read Chapter 35, 37 No lab broadcast 3/27
Chapter 35 – Fri. 3/28

84. Leaf Modifications 1. Tendrils: for support 2. Bulbs: for food storage
Ex: Peas
2. Bulbs: for food storage
Ex: Onion
3. Insect Catching Ex: Carnivorous Plants
4. Flowers: thought to be modified leaves.

85. Other Modifications of Leaves
Tendrils
Spines
Succulent Leaves
Bracts

86. Stem Vascular Tissue
Dicots – vascular bundles join together to make a ring. Often have secondary growth.
Monocots – vascular bundles are scattered. No true secondary growth.

88. Secondary Growth Growth in diameter.
Growth from lateral meristems or cambiums.

89. Cambium Types 1. Vascular – produces xylem and phloem.
2. Cork – produces “cork”.

90. Vascular Cambium Location: between primary xylem and phloem.
Produces: secondary xylem and phloem.

91. Fibers
Phloem
Vascular Cambium
Xylem
Fibers

92. Vascular Cambium: Cell Maturation
Internal  xylem
External  phloem
The VC pushes the xylem and phloem apart from each other.

94. Result Newest xylem is next to the cambium.
Oldest xylem is in the center of stem.

95. Result Newest phloem is next to cambium.
Oldest phloem is under the epidermis.

96. Result Xylem accumulates over time.
Phloem is destroyed by the outward growth and must be replaced yearly.

97. Cork Cambium Location: Cortex (external to the VC). Produces: Cork
Comment – commercial cork is harvested from a Cork Oak.

98. Cork Cells Produced "outwardly" only.
Covered with suberin and are dead when mature.
Function – insulation and protection.

99. Epidermis
Cork Cambium
Fibers
Cortex
Phloem
Vascular Cambium
Xylem

100. Bark All tissues external to the VC. Includes:
Phloem (1 degree and 2 degree)
Cork
Cortex
Epidermis
Fiber cells

102. Wood Xylem tissue of a dicot stem.
Comment – monocots don’t have VC and technically don’t produce true “wood”.

103. Xylem Growth Springwood - Large cells Rapid growth
Summerwood - Small cells Slow growth

104. Annual Rings
Formed by the growth difference between springwood and summerwood.
Usually one produced per year.

105. Comment Ring size varies by climate and growing conditions.
Rings can be used to date wooden structures.

106. Summer Wood
Spring Wood
One Year’s Growth

109. Angiosperms Divided into two main types: 1. Dicotyledons or Dicots
2. Monocotyledons or Monocots
Cotyledons = seed leaves

110. Monocots vs. Dicots 1. Seeds and embryos 2. Leaves 3. Stems 4. Roots
5. Flowers

112. Seeds and Embryos Dicots - no endosperm. - 2 cotyledons.
Monocots - endosperm cotyledon

113. Leaves
Dicots – netted veins.
Monocots - parallel veins.

114. Stems Dicots - ring pattern - vascular cambium
Monocots - scattered pattern no vascular cambium

115. Roots Dicots - taproot. - xylem centermost tissue.
Monocots - fibrous roots pith centermost tissue.

116. Flowers
Dicots – parts in 4's or 5's.
Monocots – parts in 3's.

117. Summary Know the main organs of plants and their functions.
Know the main cell types or tissues in plants and their functions.

118. Summary Know the structural organization of stems, roots, and leaves.
Know the differences between dicots and monocots.