parts of the stem what does a stem...
TRANSCRIPT
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Selected plant parts and what they “do”
Vickie Liskey
Botany for Master Botany for Master Botany for Master Botany for Master Gardeners Part IIGardeners Part IIGardeners Part IIGardeners Part II
What you should know by the end
of today’s session
How to tell a stem from a root
How to recognize a simple and compound leaf
How to describe how water gets to the top of trees
How to tell a monocot form a dicot
What does a stem do?
Physically support leaves, flowers & fruits
Transport water, minerals & nutrients
Provides storage in some plants
Parts of the stem
Note: Stem parts are important in plant identification!
node = place where leaf is
(or was) attached to the stem
internode = distance
between nodes
terminal bud
axillary or lateral bud
leaf scar
bud scale scar
node
bud scalesOne year of growth from one bud scar to another
http://www2.una.edu/pdavis/images/trees/twigs/fraspcm.jpg
A closer look at buds
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lateral bud
leaf scar bud scale scars
Let’s review
Lateral or axillary buds
Located in the angle where the leaf attaches to the stem
Axillary bud
may produce lateral shoot or branch
apical meristem
internode
node
axillary buds
Terminal bud
leaf primordia
Angiosperms divided into
• Dicotyledon
Monocotyledon
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Monocots
• Fibrous root system• Vascular system in
bundles• No secondary growth• Meristems not in
terminal buds• Parallel venation
• Flower parts in 3’s• Vascular bundles are
scattered in the stems• One Cotyledon
How does grass grow?
Dicots
• Fibrous or tap root system• Vascular system forms ring in the stem
• Secondary growth common• Net venation
• Two cotyledons• Flower parts in 4’s or 5’s
•
Dicot training
• Knowing a plant is a dicot is important when you prune or pinch to shape growth.
• Removing terminal buds causes the removal of the hormone auxin that keeps the lateral buds dormant or slow growing.
• This allows you to shape the plant.
Why is a Christmas tree a triangle and not a rectangle?
Monocot Versus Dicot Plants
• Important monocots are rice, wheat and corn; oak trees and dandelions are dicots.
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What’s inside the stem?
cortex cells add structural strength to the stem
vascular bundles
corn
vascular bundle
xylem
phloem
on the outside
on the inside
Notice the positions of the tissues as related to the outer layer of the stem!
xylem
phloemWhat does the phloem do?
transports nutrients in sap
What does the xylem do?
transports water and minerals
o Carry H2O & dissolved nutrients
o Cells are:
o long, open-ended, connected end to end
o have thick cell walls
o resemble straws
Xylem cells
Phloem cells
o Transport actively photosynthetic products
o from leaves to roots, stems, flowers & fruits
o Cells are:
o long and tube-like
o without extra cell wall thickening
Herbaceousmonocot (corn)
Stem cross-sections
Woody dicot(maple tree)
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vascular cambium
vascular cambium
bark
phloem
xylem
What’s this area?
www.unlv.edu/.../ Secondary/Secondary.html
vascular cambium
phloemxylem
barkVascular cambium
o Cambium is a meristematic tissue, meaning it divides to produce new tissues
o Cambium divides to produce
o xylem: to the inside (heartwood, pith)
o phloem: to the outside (part of bark)
o Responsible for “girth growth,” or increased stem diameter in woody plants
?What is bark?
Answer. Bark is the outer layer of cells on a tree containing
cambium, compressed phloem, and cork
What do roots do?
o take up water and minerals
o anchor the plant
o store food reserves in over-wintering perennials
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Kinds of root systems
o tap root, can be large of narrow
o fibrous or lateral roots form a network in the ground
What’s inside a root?
?How does this differ from a
stem?
buttercup
Answer: The vascular system is in the center
What’s inside a root?
buttercup
xylemcortex
phloem
cambium in woody roots
Unique to roots!
root cap -located at root tip & protects growing point
root cap
Root hairs on a radish seedling
Root hairs, another unique feature
?What is the function of root hairs?
Answer: Absorb water and minerals from the soil
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What do leaves do?
o photosynthesize
o respire
o transpire
Major leaf parts
• lamina (leaf blade) -highly variable in size and shape
• petiole - stalk at base of leaf that attaches leaf blade to stem
http://www.csdl.tamu.edu/FLORA/201Manhart/veg/leaf.venation/image1.gif
Leaf vein patterns
Compound vs. Simple leaves
Hint: Where is lateral bud?
Simple leaf
Buds are in the axils between leaf and stem
Compound leaves
pinnately compoundpalmately compound
leaflet
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Simple or compound?
Where is the bud?pinnately compound
leaflet
?
simple ? palmately compound
leaflet
?
?pinnately compound ?
Albizzia –bipinnately compound
http://www.eeb.uconn.edu/Courses/EEB271/Fabales/Albizzia%20leaves.jpg
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What is photosynthesis?
Answer. Photosynthesis is the process whereby plant use the energy of light to convert carbon
dioxide and water to sugars
Sugars produced through photosynthesis are the building blocks of life as we know it
carbon dioxide,
water
sugars
oxygen
water
InOut
The photosynthesis factory
What is respiration?
Answer. Respiration is the opposite
of photosynthesis
In respiration, sugars, water, and oxygen are used and carbon dioxide and water are released
True or False ?
Only plants photosynthesize and only animals respire
Answer: Only plants photosynthesize but both plants & animals respire
Epidermis
What is the leaf epidermis?
Answer: The epidermis is the top and bottom layer of cells on a leaf
Leaf model
mesophyll
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open closed
What do stomates do?
Stomates are small pores on the leaf epidermis used for gas exchange
What is transpiration?
Answer: Transpiration is water loss (as vapor) from a plant
Transpiration rate is controlled by opening and closing of the stomates, which is influenced by humidity, temperature, and light
Finally!
Putting it all together
?How does water get from the soil to the top of a
tree?
The Elements . . .
Stomates control evaporation which creates a lower pressure in the vascular system
Root hairs (often with the help of mycorhizzae) absorb water from the soil
Xylem cells transport water via capillary action and cohesive force of water
Let’s review
Name three critical processes carried out by leaves
Answer: photosynthesis, respiration, and transpiration
What role does transpiration play in water movement in plants?
Answer: transpiration creates a lower pressure in the vascular system which draws water from the soil
What do flowers do?
o reproduce – It’s all about sex
o if fertilization occurs, seeds are produced and carried in cones (conifers) or fruits (flowering plants)
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flower
It is not always what it seems!
Parts of a flower
stigma
anther
filament
style
Lily
Flower parts
anther
stigma
sepal
poplar alder
Kinds of plants with catkins are usually imperfect. Can you think of more examples?
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Remember, It’s All About Sex!
Ovary
cross-section of ovary
pollen on sticky surface of stigma
Fertilization pollen grains
ovary
pollen tube
ovule
The old birds and bees thing
beetles wind hummingbirds
Guess the pollinator
big leaf maple cape fuchsiawillow
butterflies flies bees
Guess the pollinator
yarrow skunk cabbage cat’s ear
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Fun Activity Capon B, 1990. Botany for gardeners, Timber Press, Portland OR, 220 pp. ISBN 0-88192-258-7 (paper).
ResourcesResourcesResourcesResources
Elpel, Thomas. 1967. Thomas J Elpel’s herbal field guide to plant families, 4th ed., HOPS Press, Pony, MT, 196 pp. ISBN 1-892784-07-6.
ResourcesResourcesResourcesResources
Baumgardt, John Philip. 1992. How to identify flowering plant families: a practical guide for horticulturists and plant lovers. Timber Press, Portland, OR, 269 pp. ISBN 0-917304-21-7.
ResourcesResourcesResourcesResources
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Acknowledgements Web Sources
UC Davis
U Texas
Purdue U
OSU
UCLA
Rutgers U
Princeton U
Texas A&M U
U HI
Queens U Charlotte
U IL Urbana-Charlotte
U AZ
U Miami
Cleveland St U
Wilkes U
Stony Brook U
U WI – Stevens Pt
U Florida
WSU
UC Berkeley
CA St U Stanislaus
Botanical Soc America
Southern IL U
U KY
U WI – Madison
IA St U
Eastern OR U – La Grande
U of MD
Vanderbilt U
MI St U
Grand Rapids Comm C
Cornell U
Maricopa Comm C
U CT
U Chicago
CO St U
Ohio St U
U NE Lincoln
U NM
U System GA
U North AL
Sidwell Friends School
Stanford U
Texas Tech U
Many photographs by Linda R McMahan, OSU Extension,
Yamhill County
Some slides from an original presentation prepared by Ann Marie VanderZanden