9. Stem Anatomy- xylem
The rings seen in
many trees
represent one
growth increment.
Growth rings
provide the grain
texture seen in
wood.
10. Stem Anatomy- xylem
Tracheids– cells
used for
conducting water
& minerals.
Conifers only
have tracheids
and are thus
considered
softwooded
species.
Hardwood species
have vessel
elements in
12. Stem Anatomy- xylem
Fibers are cells
with heavily
lignified walls
making them stiff.
Many fibers in
sapwood are alive
at maturity and
can be used for
storage.
14. Stem Anatomy- xylem
Parenchyma–
living cells used
for storage, cell
division, and
decay defense.
Rays are radial
parenchyma
cells.
Parenchyma cells
give rise to
adventitious
tissues.
16. Stem Anatomy- bark: phloem
Phloem tissue
makes up the
inner bark.
However, phloe
m is living
vascular tissue
formed from the
vascular
cambium.
17. Stem Anatomy- phloem
Sieve tube
elements– cells
that actively
transport
carbohydrates
from the leaves
down the stem.
Conifers have
sieve cells
instead.
20. Autumn Leaf Fall
Trees that
keep their
leaves are
evergreens,
trees that
lose their
leaves are
deciduous.
Abscission zone– area at the
base of the petiole that breaks
down and causes leaf (or fruit)
drop
21. Autumn Leaf Fall
Declining intensity of sunlight triggers the
processes leading up to leaf fall in autumn.
Chlorophyll
reduces,
unmasking
carotenoids.
Clogged phloem veins
trap sugars in the leaf
and promote
production of
anthocyanins.
27. Mycorrhizae
Is a symbiotic relationship- mutually
beneficial- with a tree and a fungus
Fungus increases surface area of
roots
Facilitates uptake of minerals that are
otherwise unavailable
Fungus gets to share the tree’s
carbohydrates.
37. Image credits:
Dr. Ed Gilman and Scott Jones, University of
Florida
Sharon Lilly, ISA Arborists’ Certification Study
Guide
Natural Resources Canada website
www.nrcan-rncan.gc.ca
Kathy Ripke, University of Minnesota
Department of Horticultural Science
Taiz and Zeiger, 1998. Plant Physiology, 2nd
ed.
Ground tissue- when a stem is green, it is where photosynthesis occurs. This is storage and support. Becomes less prominent as a stem gets larger. Most of the tissue in a tree trunk is xylem.Pith never enlarges with diameter growth- in a mature tree, it’s still very tiny in the center of the wood (xylem)
Remember, Meristems are regions of cellular growth. Cambiums are Secondary Meristems, meaning they are responsible for lateral growth
1- conduction of water and dissolved minerals2- support3- carbohydrate storage4- defense against disease and decay
Usually only a few rings in the outer portion of the wood conducts water- sapwood. Heartwood is nonconducting tissue that contains no living cells.
Non living
Trees with wide vessel elements early in the year are called ring porous. diffuse porous.
Nonliving in the rest of the wood
Adventitious tissues contain dormant buds that produce epicormic sprouting when the tree is under stress or loses its normal buds.Axial or radial transport
So remember we have the cork cambium that produces the outer bark. The vascular cambium produces both the xylem and the phloem.Phloem moves the sugars produced in leaves during photosynthesis to other parts of the tree for storage and consumption. Unlike xylem, which creates diameter growth each year, old phloem gets crushed and resorbed or becomes part of the bark.
Very slow process, requires energy to move sugars.
Think of these as the “engine room”Phloem moves sugars both up and down the stem. Xylem only moves water up. Stump treatment.Source and sink- sugar transport
Leaves are where all the action takes place… we’ll get to those in a moment.Vascular tissues, we covered that. Cuticle. Photosynthesis- Palisade parenchyma and spongymesophyll. Chloroplasts, chlorophyll. Transpiration- loss of water which moves water up the xylem. Stoma. Spongy mesophyll- flexibility, water vapor among.
The leaves of broadleaved plants are thin and are not protected by any thick coverings. The cell fluids are usually watery and freeze readily. Tissues unable to overwinter must be sealed off and shed to ensure the plant's continued survival. The separation layer also protects the stem from moisture loss and disease.
2-3x diameter of crownMost are within the top 18” soil
Large roots-Anchorage, storage, conductionAbsorbing roots- have cells modified into root hairs for taking up water and mineralsTap root- usually get choked out or restricted in downward growth in mature trees.Apical meristemGeotropismOsmosis
Ground tissue- bulk of the roots- for storage, support, and uptake.
Chloroplasts, chlorophyll, why leaves are greenBreaking the carbohydrate bonds releases energy, used for all its biological functions
Transpiration is the loss of water from the leaves through evaporation.It moves water and mineralsup the tree, like sucking water up a straw. It also cools off leaves.Rate of water movement depends on T, humidity, and soil moisture.Guard cells around stoma open and close to prevent evaporation, but also allow CO2 in for photosynthesis. Usually open during the day.Cuticle, leaf hairs, sunken stomata- adaptations for dry/hot conditions.
Excurrent- apical dominance (apical bud). Effects of removal.Pine tree rarely looks decurrent, due to it’s genetics.However, will a tree planted on an urban street attain the size that the same tree in the woods will?
1- upper and lower vascular elements plug- limit vertical spread of decay.2- wall formed by the last cells of the growth ring (axial parenchyma)- limits internal spread3- wall formed by ray cells- limiting lateral spread4- strongest, new growth ring that forms after injury
A top down view.None of these walls are infallible.
Monocot- like grassesIrregularly scattered vascular bundles. Since there’s no rings and annual production of xylem, palms never increase in diameter.Vascular tissue embedded in very strong fibrous tissue. Parenchyma cells for storage.No CODITOnly ONE apical meristem, if lost, it will die.
Seedling will grow a single root, then all others are adventitious coming from the base- root initiation zone.Most roots are close to the stem, forming a root mat.No secondary growth, never increase in diameter.Also form mycorrhizal associations
