Tree Anatomy Arlington and Alexandria Tree Stewards Jim McGlone Urban Forest Conservationist Virginia Department of Forestry
Tree Structure
https://thelandscapebelowground.com/wp-content/uploads/2018/03/poster-tree-100dpi-black-and-white.jpg
Roots and Branches: Similar but not the Same Roots Absorbing small structures that support energy system through water collection Structural larger roots that collect and support absorbing roots Buttress roots very large roots that connect/support trunk and root system Branches Twigs small structures that support energy system through leaves Branches large stems that collect and support twigs Scaffold branches very large branches that connect crown to trunk
Types of tissue in trees Meristem cells capable of division and differentiation Vascular Xylem and phloem; conducts water and nutrients from roots to crown, and translocates photosynthate Ground everything else Fibers in stems and seeds generally dead cells Parenchyma lots of things, but mostly photosynthesis, carb storage and defense; living non-reproductive cells Epidermal outermost skin; control gas and water exchange
A Closer Look Xylem Growth Ring Early Wood/ Late Wood Fibers Divide Parenchyma
Tree Phsyology
(Very) Basic Outline Plants create biochemical energy (sugars) through photosynthesis Sugar, water and nutrients are moved around the plant through vascular system Living cells burn sugar in presence of oxygen through cellular respiration (Kreb s cycle) to produce ATP ATP fuels the production of biochemical that are used for: Cellular repair Defense New tissues (meristem only) Photosynthesis takes place in the parenchyma Respiration takes place in parenchyma and meristem
Photosynthesis 6CO 2 +6H 2 O C 6 H 12 O 6 +6O 2 Inputs: CO 2 from air via stomata H 2 O from roots via xylem Sunlight Output: Sugar
Cellular Respiration C 6 H 12 O 6 +6O 2 6CO 2 +6H 2 O+3ATP Inputs: Sugar from leaves Oxygen from lenticels, mainly in roots Output: ATP to ribosomes Ribosomes use ATP and Nutrients to make new tissues and toxins and for cell maintenance
Tree Energy Model Sunlight Tissues Maintenance Toxins CO 2 Sugar Sugar Water Nutrients Oxygen
Tree Growth
How does a tree grow? Primary Meristem AKA Buds Elongates into shoots Produces Cortex Epidermis Lateral buds Or becomes a leaf Or becomes a flower Secondary Meristem AKA Cambium Located between bark and wood Produces vascular tissue Xylem persists as wood and moves water and nutrients Phloem becomes bark or is reabsorbed and moves sugars Produces parenchyma and fiber
Heart Wood Dead tissue Created by parenchyma Defensive chemicals Tyloses (air bags) No photosynthate Usually darker than sapwood
Reaction Wood
Tree Cross Section http://dendro.cnre.vt.edu/forsite/tait2.htm
Growth and Branch Attachment Primary growth (shoots) Secondary growth starts at the top and goes down Branch gets new layer Then trunk get new layer Trunk growth attaches to and wraps branch growth Branch reaches to center of tree Good attachment has U shape and branch bark ridge
Good Branch Attachment
Bad Branch Attachment 2005 International Society of Arboriculture, Introduction to Arboriculture: Pruining
Tree Growth and Wounds CODIT: Compartmentalization Of Decay In Trees
CODIT and Growth Remember ONLY meristem can make new cells So trees do not replace lost tissues, they seal off decaying wounds Some of the barriers are laid down during growth Others are created in heartwood In sapwood parenchyma can create and reinforce barriers chemically
CODIT
CODIT
Tree growth and Hormones
Auxin A primary hormone Produced in buds Wakes up the plant Travels from the buds to the roots to stimulate cytokinin production and root growth. Plays a role in bud supression
Suppressed Buds
Auxin
Cytokinin Produced in roots Stimulates cell division Follows Auxin pathways up to shoots Signals stomata to open
Cytokinin
Apical Dominance
Auxin & Cytokinin When top is hurt and buds are lost, tree has a lot of cytokinin and little auxin so cytokinin promotes stem growth When roots are hurt, tree has lots of auxin and little cytokinin so auxin promotes root growth
Other Plant Hormones Gibberellin Promotes cell elongation Used to lengthen grape cluster stems Abscisic Acid Anti-auxin Promotes dormancy and senescence Causes leaves to change color in Fall Signals stomata to close Produced in abscision zone Eythylene Readies abscision zone between leaf petiole and stem Growth inhibitor Ripens fruit
Application: Pruning
Before We Begin Remember Pruning is Wounding Reduces photosynthetic area and food production Opens pathways for pathogens Forces tree to expend energy on wound closure
WHY PRUNE? Maintain Health Reduce Risk of Failure Provide Clearance Influence Flower or Fruit Production Reduce Shade and Wind Resistance Improve View Improve Aesthetics
Pruning, growth and hormones Trees evolved to lose branches due to forest shading At branch collar, meristem is primed to create reaction wood and tree stores defensive chemicals Good cuts can help tree s CODIT response Through hormones, terminal bud(s) suppress lateral buds Hormones system creates a hierarchy of buds that can be manipulated through pruning to control tree growth All pruning should be done at branch unions, except for very specialized pruning (e.g. pollarding and coppicing).
Branch Collar and Branch Protection Zone
Poplar self pruning eyes
3 cut method 1 st cut is partial on compression side to prevent tearing 2 nd cut is complete and above 1 st cut to remove weight 3 rd cut is complete and removes stub
Reduction Cut After 1 Year
Reduction Cut After 3 Years
Tree Hormones and Reduction Terminal Bud Produces Most Auxin Cytokine Follows Auxin Pathway Causing Shoot to Grow Reduction Replaces Terminal Bud and Reduces Auxin Pathway Reduces Growth of Branch Relative to Other Parts
1 October 2008 2
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October 2008 March 2011 2016
October 2008 March 2011
October 2008 2
October 2008 March 2011
Application: Planting
Planting Issues Roots and canopy need to be in balance so roots can provide enough water for photosynthesis Roots expand radially from trunk in a disc Trees are native to uncompacted, organic rich soil Transition from trunk to root occurs at ground level
Comparison of Small to Large Sized Nursery Stock https://hort.ifas.ufl.edu/woody/maximum-size.shtml
Squaring the Circle Pictures from Colorado State Extension at: http://csuhort.blogspot.com/2014/03/arbor-day-is-comingtree-planting-101.html
Application: Diagnosis
Cavities
Soil Compaction/ Flooding Sunlight Tissues Maintenance Toxins CO 2 Eliminates macro-pores, which hold air Impairs respiration Water Sugar Nutrients Oxygen
Inadequate Soil Sunlight Tissues Maintenance Toxins Restricted Root Growth CO 2 Sugar Inadequate water and oxygen Water Sugar Impairs entire energy system Nutrients Oxygen
Soil volume Casey Trees
How Does a Tree Respond to This? Insufficient energy production to support new sapwood growth Lowered defenses Cannot maintain roots
Sprouting What do the sprouts need to grow? What happened to allow the sprouts to grow? Where is the problem with this tree?