Why do Trees Live so Long?
Superlative Trees
Bristlecone Pine
Giant Redwoods
What features allow humans to live to 100?
Cruz Hernandez died in 2007 at the age of 128.
• Luck
• Good genes
• Good diet
• Healthy behaviors
• Good immune system
• Protection from environment
So, what allows trees to live to 3,000 + years?
• Luck • Protection
– Chemistry – Thick bark – Shelter sensitive tissues from winter
• Redundancy • Continued growth • Clonal growth • Repair mechanisms • Genetics and intense selection
early in life
Tree Morphology
What is woody growth?
• Review
– Primary Growth—all plants • Apical meristems—reaching growth
– Shoot apical meristems in buds
– Root apical meristems at root tips
– Secondary Growth—woody plants • Lateral meristems
– Vascular cambium separating bark and wood
– Cork cambium within bark separating inner-living bark and outer-dead bark
MERISTEM???
Stem cells that are perpetually young and capable of dividing to give rise to new tissues
and organs—think of human stem cells.
Primary Growth
• Occurs near stem and root tips
• Reaching growth
• Establishes pattern of leaf and branch production
• Apical meristem of shoot hidden by protective bud scales
• Length of primary growth displayed between terminal bud scale scars
The Tree that Owns Itself
Athens Georgia
Quercus alba
This white oak in Athens GA owns
something that no other city tree
owns. What does it own?
Rambutan-- Nephelium lappaceum
“hairy” fruit
Related to Lychee
Soapwart Family
Grape-like flesh—seed is bitter
Apple Question
Important Dates
Transport to Labrador Pond
Vascular cambium produces more wood
to the inside and more phloem and inner
bark to the outside.
Secondary Phloem
Secondary Xylem
• Several developmental genes in shoot apical meristems ARE ALSO functioning in the vascular cambium – Gene expression in apical meristem of
Arabidopsis (herb) compared with vascular cambium of Populus (tree)
– Class III Homeodomain-leucine zipper – KANADI Transcription Factor – MIR 165/MIR 166 microRNAs – Meristem Maintenance (SHOOT
MERISTEMLESS) – CLAVATA1-cell receptor kinase, but not
CLV3
• Overlap in use of developmental genes
• NO “tree gene”
Terminal and Lateral Bud Variation
Leaf Scar Variation
Lenticels
Speckled Alder—Alnus incana subsp. rugosa
Lenticels are ruptures in old outer bark
that creates ventilation spaces.
Pith-soft spongy tissue in the center
of stem formed from apical meristem;
function???
Cornus-dogwood
Solid Pith
Nyssa-blackgum
Diaphragmed Pith
Walnut—Juglans
Chambered Pith
Quercus—Oak
Star-shaped in x-section
PITH
Thorns—Modified Branches Originate from Lateral Buds
Branched thorns of Honey Locust--Gleditsia Thorns of Hawthorn--Crataegus
Spines—Modified Stipules Originate adjacent to leaf petiole
Black Locust is an example
Prickles are Epidermal Outgrowths Examples include Rosa and Rubus
Thomas, P. 2000.Trees: Their Natural History.
Chalk Board Illustration of
Primary and Secondary Xylem and Phloem
Vascular cambium
Cork Cambium
Inner and Outer Bark
Suggested Historic Dates between 1628 and 1995?
Sapwood & Heartwood
www.bethlehamolivewood.net
Sapwood-functional in water transport;
1-4 rings in ring porous species;
10+ in diffuse porous
Size of sapwood is proportional to size of canopy (LAI)
Heartwood usually lacks living parenchyma cells
darker color due to tannins, resins,
gums, & polyphenols
English Longbows from Yews
http://www.selfbow.com/
Yew heartwood is compression resistant
inside of bow
Yew sapwood is stretch resistant
outside of bow
Long range heavy-tipped arrows to
penetrate armor
Composition of Wood
• Wood=xylem
– 40-55% cellulose
– 20-40% hemicellulose
– 18-35% Lignin • Large, complex molecule
• Important preservative
• Important in organic soil
• Lignin makes wood hard!
Tannins are generally found in bark
• Inhibit bacteria growth
• Make soil acidic
• Bind proteins and inhibit enzymes
• Anti-herbivore chemical
• Why are their few plants in a hemlock forest?
Annual Rings
• Temperate & polar regions
– Less predictable in tropics
• Story teller of the tree
– Fire
– Frost damage
– Insects
– Precipitation
– Competition
– Temperature
– Sunlight/Volcanism
The Tree that Ate the Bicycle
• “A boy went to war in 1914 and left his bike chained to a tree. He never came home and the family left the bike there as a memorial to the fallen soldier.”
• Puget Sound Washington
Ring versus Diffuse Porous Wood
Ring porous wood has the vessel
elements concentrated in the
spring wood.
Diffuse porous wood has the vessel
elements scattered across spring
and summer wood.
Ring Porous Wood
• More common in mid-latitudes; uncommon in tropics
• Ring porous species have determinate annual growth
• Earlier growth in spring than diffuse porous
• Quercus, Carya, Juglans, Castanea, Ulmus, Platanus
Diffuse Porous Wood
• Vessel elements medium sized—smaller than ring porous vessels
• Most common, especially in tropics
• More likely to experience indeterminate growth
• Acer, Aesculus, Betula, Fagus, Tilia
Angiosperm versus Gymnosperm Wood
• Angiosperm wood
– Hardwoods-fibers make wood hard
– Heterogeneous—fibers, tracheids, vessels
– Wide rays
• Gymnosperm wood
– Softwoods—mostly tracheids
– Homogeneous—wood cells of similar size and shape
– Thin rays
– Presence of resin ducts
– No pattern of ring or diffuse porous
Gymnosperm Wood Soft woods—no fibers
• Tracheids with bordered pits are the dominant support and water transport cell.
• Air embolisms are sealed as torus is drawn towards edge of tracheid
• Gymnosperm advantage in cold & dry environments.
• Slower water movement
• Slower water loss from leaves
• Survive winter cavitation and drought
• Other traits?
Gymnosperm Advantage
in Boreal Forest and the Adirondacks
Tell me about this photo
• Temperate zone
• Ring porous
• Distinct vessel elements
• Identify summer & spring wood
• How old is the sample
• Determinate or indeterminate growth
Quercus rubra
Wood Grain—Spiral vs. Straight
• Rarely vertical
• Up to 40°
• Pine breeders select for straight grain—why?
• Advantage to Spiral – Even distribution of water,
minerals, and carbohydrates
– Greater wood strength
Frost Scars (i.e., frost ribs)
• Freeze drying in winter
– Wood shrinks & cracks in winter
• Repeat scaring along branches and trunk
• Snap, crackle, and pop
Winter Sun Scald
• Low winter sun warms bark and stimulates day time growth
• Extreme cold kills these cells after sunset
• What side of the tree trunk will this be found?
• What can one do to protect the tree?
• Usually thin-bark young trees
Burls Cancer-like growth of wood where the cause is largely unknown; virus,
bacteria, insects—result in abnormal growth of dormant buds.
Betula alleghaniensis-Tree Sloth
Camp Huntington Sequoia—Phallus Burl
Quercus alba just north of Aurora NY
Burls can be Desirable
Redwood Burl Guitar found
on Ebay and Redwood Burl Furniture
Burls have “confused grain”
http://www.portmcneillbc.com/
World’s Largest Burl
361 year old Sitka Spruce from Vancouver
22 tons
45 feet in circumference
Tree Branching and Knots Longitudinal section of Trunk and Branch
Annual Rings
Annual rings in branch grow
confluent with annual rings in trunk
This area will form a TIGHT knot.
Tight Knots
Tree Branching and Knots
When the branch dies, the trunk slowly engulfs
the branch by adding more secondary growth.
A LOOSE knot forms where the trunk grows
around a dead branch leaving a collar
of deadbark around the knot.
Loose Knots
How to eliminated Loose Knots?
• Branch collar
How to eliminated Loose Knots?
• Remove branches as they die.
• Cut back to branch color to improve recover—not flush with the trunk.
• 1st-underneath and away from collar
• 2nd-above and closer to collar
• 3rd—remove left over stub to collar
1
2
3
Reaction Wood in Conifers
Gravity
Reaction Wood = abnormal wood that
is produced in leaning trunks
and horizontal branches.
In Conifers, reaction wood forms
on the lower surface and
is referred to as compression wood.
Smaller tracheids
with heavily lignified cell walls
Reaction Wood in Angiosperms
Gravity
Wood fibers in tension wood have a layer of
gelatinous cellulose in the cell wall.
Wide rings with many fewer vessels,
if present then conspicuously smaller.
Compression & tension wood make poor lumber!
Trees and Music
Amazon Rosewood
African Padauk
-hard dense tropical woods
that resonate for long
periods of time
Spruce & Maple -softwoods that vibrate easily
Keys-beech or hornbeam -longevity and hardness
-does not change shape
Bassoons—Norway Maple --precision drilling, moisture abs without shape change
Tropical Pernambuco -stiffness and hold tension on strings
Concert Hall Acoustics
Bark
Inner Bark contains functional, living phloem;
Bulk flow of sucrose to growing tissues.
Inner Bark parenchyma are totipotent
and capable of wound responses.
Bark Arrows indicate Cork Cambium
Outer bark (i.e., periderm) contains dead phloem;
new and old cork, new cork cambium
Cork Cambium regenerates every year.
Bark Variation
Differences in bark
are due to the pattern
of periderm formation.
Bark Characteristics Change with Age
Betula alleghaniensis
Spandex Bark
Fagus grandifolia
Periderm of Quercus suber
http://www.heartsong.typepad.com/goodearth/
Cork Harvest Portugal
http://www.cuyamaca.edu/ohweb/Australia%20Photos/Melbourne%20Photos.asp
Summary of Secondary Growth in Trees
• Patterns in Wood
– Annual rings
– Heartwood & sapwood
– Ring vs. diffuse porous
– Loose vs. Tight knots
– Reaction wood • Compression
• Tension
– Scarring • Burls
• Frost ribs
• Sun scald
• Patterns and Functions of Bark
– Inner bark
– Outer bark or Periderm
– Regenerative properties