Download What is a Tree? - Illinois Arborist Association

ISA Arborist
Certification Training
Chapter 1 – Tree Biology
Illinois Arborist Association
Arborist Certification
Training
September 1, 2015
Presented by:
Ben Reynoso & Eva Saunders
What is Tree Biology?
The study of
tree structure, the
function of those
structures and the
interrelationship
between both.
Photo Credit: Mark Duntemann
What is a Tree?
  Long-lived
perennial
  Woody
  Compartmentalizing
organism
Photo Credits: Mark Duntemann
Types of Trees
  Deciduous
(oaks, maples, ash)
  Deciduous Conifer
Photo Credits: Mark Duntemann
(larch, baldcypress)
  Coniferous
(pines, spruces, firs, junipers, yews)
Tree Form
Excurrent trees:
  Strong central lead
  Most young trees
  Conifers, sweet gum
Graphic: Urban Tree Foundation
Photo Credit: Missouri State University
Tree Form
Decurrent trees:
  Lateral shoots outgrow
original terminal shoot
  Round-headed tree
  Typical of mature trees
  Oaks, elms
Graphic: Urban Tree Foundation
Plant Growth – Cellular Level
Cell growth:
A. Mitosis - cell division
B. Cell differentiation
1.  Cells change
structure to specific
function
2.  Arranged tissues
organized into organs
(leaves, stems, roots,
flowers and fruit)
3.  Organs organized to
function as an
organism-tree.
Photo: University of Wisconsin
Tree Growth
Cells & Tissues (GROWTH)
  Meristems – Cells that produce other cells
  Differentiation – Change in the cells
structure to assume a needed function
  Apical meristems – Meristems located at
the ends of shoots/buds and roots
(primary growth)
  Cambium – Lateral Meristems that produce
the tree’s vascular system (secondary
growth)
  Cork Cambium – lateral meristem that
produces bark
Tree Growth
Meristem is the tree
growth zone
Primary meristem:
  Responsible for
elongation of roots
and stems
  Located in the tips
of roots and stems
(buds)
Graphic: Michigan State University Extension
Tree Growth
Secondary or Lateral
Meristem:
 Increase in diameter
 Vascular cambium:
produces xylem or
phloem
 Cork cambium produces bark
Photo: UF Herbarium
Growth Tissue:
Cambium
Where growth occurs
Cambium produces:
 Phloem (outside)
 Xylem (inside)
Graphic: UF Horticulture
Tree Anatomy Vocabulary
  Cambium produces Xylem and Phloem
  Xylem – Is produced on the inside of the
Cambium, it is the ‘wood’ of the tree.
Moves water and minerals up to the
leaves, supports the tree and stores
sugars.
  Phloem – Is produced to the outside of
the Cambium. It moves sugars down from
the leaves
Tree Anatomy
Heartwood
  Non-water
conduction
  Non-living xylem
Sapwood
  Water conduction
  Living xylem
Cambium
  Thin layer of active
Xylem & Phloem
Bark
Graphic: Colorado State University Extension
Vascular Tissue - Xylem
Xylem is the wood of trees
Functions:
  Conduction of water &
dissolved minerals
  Support weight of tree
  Storage of carbohydrate
reserves
  Defense against spread
of disease & decay
Vascular Tissue Xylem
Composed of dead & living
cells
  Tracheids – water
conduction & support
  Fibers – mechanical
strength
  Parenchyma cells-help
maintain water balance &
store carbohydrates
  Vessels – hardwood trees
Graphic: Sonoma State University
Vascular Tissue Xylem
 T ransportation of water
and minerals
 T ranspiration is the loss
of water through leaves
 Water molecules are
pulled in long, hydrogenbonded chains from root
to leaf
Graphic: University of Washington
Vascular Tissue Xylem
  Water conduction occurs
in sapwood
•  Conifers – 2-12 rings
may conduct water
•  Hardwoods – outermost
1 or 2 rings especially
elm trees
  Non-water conduction –
heartwood (darker in
color than sapwood)
Graphic: University of Minnesota Extension
Vascular Tissue: Phloem
  Food transport
  Cells are living
•  Sieve cells (conifers)
•  Sieve tube cells
•  Companion cells
•  Parenchyma cells
Graphic: Pacific Union College
Vascular Tissue - Phloem
  Translocation:
conduction of
sugars produced
in the leaves to
other parts of the
plant
  Photosynthate
moves from
source to sink
  Sinks – plant
parts that use
more energy than
they produce
Graphic: UF Horticulture
 Axial transport –
materials flow up
and down
 Radial Transport –
parenchyma cells
that extend across
(radial) xylem and
phloem
•  Transport sugars
•  Store starch
•  Restrict decay
Vascular Tissue
Bark
Function:
  Moderates interior
temperature
  Reduces water loss
  Protects against
injury
Composition:
  Nonfunctional
phloem & corky
tissues
  Contains wax and
oil to minimize water
loss
Photo: East Tennessee State University
Bark
Lenticels are small
openings that permit
gas exchange
Photo: Colorado State Extension
Tree Organs
  Leaves
  Stems
  Roots
  Flowers
  Fruits
Leaves
Primary Purpose is
Photosynthesis:
Inputs:
 Carbon dioxide
 Water
 Light
Outputs:
 Carbohydrates/sugar
(Photosynthates)
  oxygen
Graphic: Butler University Herbarium
Leaves
Stomata
  Control loss of water
vapor (transpiration)
  Control gas exchange
Guard cells
  Light, temperature,
wind and humidity
  Open-day, Closenight
Photo: University of Hawaii at Manoa
Antitranspirant Sprays
Artificially close stomata cells to
prevent water loss during drought
or dormant times.
Reduces photosynthesis, cooling of
leaves, and carbon dioxide uptake
Leaves
Fall foliage color:
  Triggered by short,
sunny days with cool
nights
  Sugar accumulates &
chlorophyll breaks
down
  Other pigments show:
•  Anthocyanins: reds
& purples
•  Carotenoids:
yellows, oranges &
reds
Photo: USDA
Leaves
Deciduous Trees
  Leaves lost are the result
of cell changes and
growth regulators
  Abscission zone at stem:
•  Enable leaf drop in fall
•  Protect leaf area
against desiccation &
pathogen entry
Graphic: University of California Davis
Modified Leaves
Arid regions:
  Thick cuticle,
leathery leaves
and few stomata
  Succulent,
water retaining
leaves or dense
hairy coverings
Photo: Texas A&M
Tree Parts - Stems
  Strongly attached
underneath but
weakly attached
above
  Branch collar –
layers of tissue,
bulge around
branch base
  Autonomousfunction on own
Photo: University of Florida (Horticulture)
Tree Parts – Stem Anatomy
  Node - gives rise to
leaves & buds
  Internode - distance
between nodes
  Terminal bud primary growth
  Terminal bud scale
scar - start of new
growth of current year
Tree Parts - Buds
1. Terminal or
apical buds located at the
end of a shoot
2. Lateral or axillary
buds - located on
the sides of the
stems.
Tree Parts - Buds
3. Adventitious
buds arise from
loss of primary
bud
4. Epicormic shootsWhen dormant
buds sprout and
grow
Photo by Joseph O’Brien, USDA Forest Service
Tree Parts - Roots
Main Functions:
  Anchorage
  Storage
  Absorption
  Conduction
Roots need water & air
for optimal growth
Photo: Louisiana State University
Tree Parts - Roots
  Absorbing roots - Small,
fibrous organs that grow
at the ends of roots and
found in top foot of soil
  Lateral or horizontal roots
near surface
  Sinker roots - Grow
vertically downward off
lateral roots and are
found w/in few feet of
trunk
Photo: University of Texas
Tree Parts - Roots
  Most roots found in
upper 1-12” of soil
  Taproot is a
downward growing
root in young trees
  Roots may extend
2-3 times the tree
crown/canopy
  Root extent and
directional growth
is the result of the
tree’s environment
rather than genetics
Wrong
Correct
Tree Parts - Roots
  Mycorrhizae - the
symbiotic relationship
of roots with certain
fungi
  Symbiosis – both
organisms benefit
from the living
arrangement
  Fungi get food & in
turn aid roots in
absorption of water
and minerals
Photo: Iowa State University Extension
Tree Parts - Roots
  Water enters young roots
or mycorrhizal roots by
osmosis
  Osmosis requires fluid
transport from higher
concentration to lower
concentration
  Reverse Osmosis: water
movement from out of
roots into soil
  Example: de-icing roads
with salt increases
(higher concentration in
soil)
Photo: Forestry Department South Australia
Allelopathy
Production and release of
chemical substances by
one species that inhibit the
growth of other species of
plants
Flowers & Fruit
Flower is reproductive
structure of plant. Once
pollinated, give rise to the fruit
or seed.
Tree Physiology
Photosynthesis
Process that converts light into sugar
and starches
 Chlorophyll is the green/leaf pigment
that absorbs sunlight.
 Chlorophyll is stored in chloroplast cells
of leaves where photosynthesis takes
place.
 Raw material required are carbon dioxide
and water.
Tree Physiology
Respiration
Energy made from photosynthesis is used
  Oxygen is needed
  Carbon dioxide and water are given off
Tree able to survive in these situations?
1. Flooded roots
2. Defoliated leaves by caterpillars
ENERGY IS RELEASED
Tree Physiology
Transpiration
Loss of water through stomata:
  Helps cool leaf during hot times and
aids water uptake in xylem
  Dependent on water, temperature, &
humidity
  90% water absorbed from roots are lost
in leaves
Tree Physiology
Control of Growth and Development
Plant growth limited by:
  Genetics
  Environment
Plant hormones
  Auxin:
•  Produced in shoots
•  Alters crown growth
•  Involved in tropisms
  Cytokinin:
•  Produced in roots
•  Shoot initiation and growth
Photo: University of Nottingham, UK
Tree Physiology
Control of Growth and Development
Hormones signal:
  Cell Division
  Cell Elongation
  Flowering
  Fruit Ripening
  Leaf Drop
  Dormancy
  Root Development
Tree Physiology
Control of Growth and Development
Tropisms:
  Geotropism-gravity response
  Phototropism-light response
Photo: University of Wisconsin
Tree Physiology
Compartmentilization
CODIT (Compartmentalization Of
Decay In Trees) a system of defense.
Graphic: USDA Forest Service
Tree Physiology
Compartmentilization
  Wall 1 resists vertical
spread, plugs up xylem
  Wall 2 resists inward
spread, plugs latewood
cells
  Wall 3 inhibits lateral
spread, activates rays
cells to resist decay
  These 3 walls form
reaction zone
Tree Physiology
Compartmentilization
Wall 4 is the layer of
wood to form after
injury has occurred.
  Strongest of all 4 walls
  Protects from outward
decay
  Barrier zone
Photo: Colorado State Extension
Palms
  Monocot
  Have no cambium
layer
  Have no growth
ring of xylem
  Have vascular
bundles of xylem
& phloem
Photo: Smithsonian Marine Station, Ft. Pierce