Biology - Jones Illinois Arborist Association

1. Tree Biology

• Grant Jones grant.jones@davey.com 630.797.8581

2. Tree Biology

In order to grow trees, we need to understand how trees grow

• Image from Internet

3. Two Trees

Image from The Body Language of Trees

4. • 5% Leaves

• 15% Stems
• 60% Trunk
• 15% Woody Roots
• 5% Absorbing
• Roots

Ratio of Whole Tree Structures Image from Internet

5. Tree Biology

• Anatomy (cellular structures)
• Morphology (organs)
• Physiology (chemical/biochemical)

6. Plant Cell (ISA Diagram)

7. • Cellulose

– (a complex sugar) Cell Wall Image from Internet

8. How does a tree go

from 1 cell to a 300 foot redwood?

• Growth
• Images from Internet

9. • Not all cells are identical.

• Specialization of each individual cell occurs after cell division, this is call differentiation.
• A cell may become the bark, flower, wood, root, etc.
• Differentiation

10. • Apical/Primary Meristem – meristem located

at tips of shoot and roots • Lateral/Secondary Meristem – residual meristem responsible for secondary growth and ultimate size trees obtain.

– Vascular Cambium – produces xylem (sapwood & heartwood) & phloem

– Cork Cambium – produces bark Meristem Types

11. Apical Meristem

• Image from Internet

12. Image from Physiology of Woody Plants by Kozlowski and Pallardy

• Growth – Lateral Meristem

13. Factors Affecting Growth

• Image from Internet

14. • Moisture

• Air
• Nutrients
• Temperature
• Light
• Environmental Factors

15. Image from ISA

• Growth Cycle

16. • Support for the tree

• Store carbohydrates
• Movement of water and nutrients
• Trunks, Stems, and Branches

17. Image from ISA

• Stem Structure (young stem)

18. Thin layer of cells that produce

xylem to the interior and phloem to the exterior.

• Vascular Cambium

19. Phloem – Sieve Tube Cells

• Image from Internet

20. Cork Cambium Initiation Cork Cambium & Cork

• Cork Cambium
• Images from Internet

21. • Tracheids – elongated dead cells with pointed

ends and thick walls containing pits • Vessels – Stacks of dead, hollow cells that form long tubes stacked above each other

• Fibers – Provide mechanical strength
• Xylem Structures

22. Images from Plant Physiology by Taiz and Zeiger

• Vessels (Angiosperm Wood)

23. Image (left) from Plant Physiology by Taiz and Zeiger

• Tracheids (Conifers)

24. • Softwood – wood

composed of only tracheids (pines, other conifers & gymnosperms).

• Hardwood – wood composed of tracheids

& vessels (angiosperms) Wood Types Images from Internet

25. Image from ISA

• Mature Stem

26. Sapwood- living wood that conducts water

• Sapwood- living wood that conducts water.

– Conifers often have 8-12 living rings.

– Angiosperms (e.g. elms, oaks) often have 1-2 living rings, while maples may have 4-6 living rings.

• Heartwood- dead xylem that does not conduct water. Sometimes darker in color than sapwood. Will form boundaries when wounded.
• Xylem (Wood)

27. • Transport from roots to shoots

• Stored energy
• Mechanical support cells with strong walls of cellulose and lignin
• Produce chemicals to resist decay
• Functions of Sapwood

28. – Ring Porous- large vessel produced in spring

and smaller vessels in summer.

– Diffuse Porous – vessel roughly the same size in spring and summer.

• Wood Types - Hardwoods

29. • Few annual rings (1-2)

• Springwood/Latewood

Hardwood Ring Porous (Oak) Images from Internet

30. • Tree-of-Heaven

• Hickory
• Chestnut
• Hackberry
• Ash*
• Honeylocust
• Coffetree
• Osage-Orange
• Mulberry
• Red/White Oak Groups
• Black Locust
• Elm
• Ring Porous

31. • Sapwood is many annual rings (4+)

Hardwood Diffuse Porous (Maple) Image from Internet

32. • Maple

• Buckeye
• Alder
• Birch
• Hornbeam
• Dogwood
• Hazelnut/Filbert
• Beech
• Holly
• Sweetgum
• Cherry (Prunus)
• Yellow-Poplar (Tulip Tree)
• Magnolia
• Black Gum/Tupelo
• Hophornbeam
• Sourwood
• Sycamore
• Poplar/Aspen/Cottonwood
• Buckthorn
• Willow
• Linden/Basswood
• Diffuse Porous

33. Formation of larger conducting cells in spring

and then smaller cells in the summer and no (or little) growth in winter create rings.

• Growth Rings

34. • Thin lines of cell that extend from the

phloem toward the pith.

• Rays transport water, sugar, and other compounds.
• Rays
• Image from Internet

35. Lenticels

• Small openings in the bark that allow for gas exchange

36. Lenticel (microscopic)

• Image from Internet

37. • Living cells linked together

by plasmodesmata • Radial and axial transport of nutrients, carbohydrates, water and other solutes

• Solutes can move in the symplast, but cells usually take up compounds they need and export those available in excess.
• Symplast
• Image from Internet

38. • Apoplast consists of the

vessels, fibers, cell walls and open spaces of the sapwood

• Water and solutes can move freely in the apoplast (transpirational pull)
• Apoplast
• Image from Internet

39. Branch Attachment

• Image from ISA

40. Image from Up by the Roots

• Branch Anatomy

41. Twig Morphology

42. Image from ISA

• Internode & Node

43. • Photosynthesis

– Sugar production • Transpiration – Water regulation and gas exchange

• Function of Leaves

44. Leaf Structure

• Image from ISA

45. • Nitrogen,

magnesium, iron, and sulfur make up the chloroplasts and chlorophyll

• Chloroplasts
• Image from Internet

46. Leaf Showing Cuticle (red)

• Image from Internet

47. • Deciduous- trees that

lose their leaves in Fall • Petiole – stalk that attaches leaf to stem

• Evergreen – trees that hold their leaves for more than 1 year

48. Fall Color

• Cool Days (not freezing)
• Shorter Days
• Bright Sunny Days
• These three factors increase sugar accumulation, which decreases chlorophyll production and allows other pigments to become visible

(anthocyanins & carotenoids).

49. • Cellular changes that allow leaf drop

• Protects region on stem from desiccation, insect invasion, and disease infection.
• Abscission Zone

50. Abscission Zone

• Images from Internet

51. Needle Drop

52. Roots

• Anchor & Support
• Absorb Water & Nutrients
• Store Water & Energy Rich
• Compound and Conduct
• Them to the Trunk
• Produce Organic
• Compounds

53. • Available Water

• Proper Drainage (no flooded soils)
• Available Oxygen (no compaction)
• Available Nutrients
• Soils roots can penetrate
• Avoid Mechanical Injury

Healthy Roots = Healthy Plants Image from Internet

54. Image from The

• Influence of Soils and
• Species on Tree
• Root Depth by Peter
• Crow

What Does a Root System Look Like?

55. Image from ISA

• Roots

56. Root Crown

57. Image from Up from the Roots

• Root Types

58. • Absorbing Roots – fine non-woody roots

responsible for water & nutrient absorption typically in top 1-foot of soil

• Root Types

59. Root Tip Anatomy

• Image from Internet

60. • Lateral Roots – Woody horizontal roots important

for supporting the tree. Typically in upper soil surface.

• Root Types

61. • Sinker Roots –

Woody vertically downward growing roots helping to anchor tree and exploit soil depth.

• Root Types

62. • True Tap (Hickory, Pine, Walnut, Coffeetree

• Heart Roots (Red Oak)
• Plate Roots (Maples, Most Trees, etc)

Image from Principles and Practice of Planting Trees and Shrubs by Watson and Himelick

• Root Systems

63. Tap Root

64. Initial root developed during seedling growth.

This root is typically choked out or diverted.

Mature trees lack tap roots.

• Tap Root

65. Heart Root

• Images from Internet

66. Plate Roots

Image (top left) from Internet. Images (bottom right and left) from Len Burkhart, PhD.

67. 1. Symbiotic (beneficial) relationship between

fungus and roots of a plant.

• Benefits:
• Absorption of water & nutrients
• Physical protection-barrier to pathogenic fungi
• Secret fungistatic substances that inhibit pathogenic fungi
• Mycorrhizae “fungus root”

68. Ectomycorrhizae Endomycorrhizae

Image from Plant Physiology by Taiz and Zeiger Types of Mycorrhizae

69. Image from ISA

• Products From Photosynthesis

70. Sugar + Oxygen

↓ Energy + Carbon Dioxide + Water Respiration

71. The process where sugars are broken

down in the presence of oxygen to release carbon dioxide, water, & energy.

• Respiration

72. • Trees under anaerobic conditions (lacking

oxygen) cannot respire.

• Living root tissue lacking oxygen (flooded soils, compacted soils) have limited respiration and can die as a result (essentially suffocation).
• All Living Cells Respire

73. Respiration

• Images from Internet

74. Image from the University of Minnesota

• All Living Cells Respire

75. • Loss of water through

the foliage in the form of water vapor Transpiration

• Image from Internet

76. • Water vapor leaves the leaf through openings

called stomata • Guard cells regulate the amount of water vapor that can exit the leaf

• Transpiration
• Image from ISA

77. • 90% through open stomata

• Stomata open during day & closed at night
• Transpiration cools leaf surface
• Transpiration increases when:

– Temps are high – Humidity is low – Wind speed increases

– Adequate soil moisture Transpiration Image from ISA

78. What has more (salt), gets more (water)!

• Osmosis
• Image from Internet

79. • Axial Transport –

Movement of water, nutrients, sugars and other solutes up and down in the tree

• Radial Transport – movement of sugars across the xylem and phloem through rays
• Image from Modern Arboriculture Transport

80. • Leaves pump sugars

into the phloem (sieve tubes) • Sugars are squeezed through the phloem which requires energy

• Most energy stays nearby
• Image from Modern Arboriculture Phloem Loading

81. • Source – Plant

structures that produce energy • Sink – Plant structures that consumer energy

• Source/Sink

82. • Heavy seed production

can be a large sink and consume a lot of energy • Heavy seed production can be a sign of stress in landscape trees

• Sinks - Stress

83. • Inhibition of the growth

of lateral buds (under hormonal control) • Removal of terminal bud can release lateral buds leading to new shoot development

• Image from ISA
• Apical Dominance

84. Single Stem-Excurrent

85. Decurrent

• Multi-Stemmed - Decurrent

86. • Suckers emerge below the graft union or from the

root system. Shoot produced from stems or roots where meristems are not normally found.

• Watersprouts form above the graft union and are typically produced from meristematic points that are carried along in the cambium (residual lateral bud).

These are sometime called latent buds.

• Epicormic Shoots

87. Watersprouts

88. Latent Bud

89. Suckers (rarely adventitious)

90. • Auxin – root initiation, cell division, apical

dominance • Cytokinin – cell division • Gibberellin – cell elongation

• Abscissic Acid – leaf abscission
• Ethylene (gas) – fruit ripening
• Plant Hormones

91. • IAA – Indole Acetic Acid (naturally occuring in the

plant.

• Synthetic Auxins – IBA, NAA, 2,4-D : used as rooting compounds and herbicides.
• Auxin

92. Orientation of growth in response to an

external stimuli (auxins involved in this mechanism).

Geotropism – response of plant to gravity (reason shoots grow upward and roots grow downward).

Phototropism – plant growth towards light Tropism

93. Image from Up by the Roots

• Geotropism / Gravitropism

94. Phototropism

• Image from Internet

95. • Compartmentalization

• Of
• Decay
• In
• Trees

Wall 1- resists vertical spread Wall 2- resists inward spread

Wall 3- resists lateral spread Wall 4- resists spread to newly forming wood

• (diagram from Shigo, 1986) CODIT

96. Aerial Roots

97. • 1 bud (apical meristem)

producing new leaves • If bud is killed the palm dies

• Fronds produced slowly (1 month per leaf)
• Damage to leaves while in the bud may take 1 year to visibly appear
• Palm Crown and Fronds

98. Palm Trunk

• Can’t compartmentalize decay
• Trunk won’t increase in width over time
• Chronic environmental stress can cause
• “pencilling” of the trunk

99. • Cabbage Palms

regenerate from root initiation zone (RIZ) • Coconut Palms will regenerate from root tip or RIZ

• Queen and Royal
• Palms regenerate more new root tips

Image (top) from Principles and Practice of Planting Trees and Shrubs by Watson and Himelick

• Palm Roots

100. Palm Trunks

• Image from A.D. Ali

101. Palm Trunks

Images (left and top right) from the Internet.

• Image (bottom right) from A.D. Ali

102. Inflorescence

103. Grant Jones

• grant.jones@davey.com 630.797.8581