Please Do Now What molecule does woody plant tissue have that green plant tissue like leaves does not Agenda Do Now Tree Notes Tree ring activity Spongy Mesophyll under the microscope Quiz ID: 482570
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Slide1
AIM: SWBAT describe the different layers in a cross section of a tree trunk
Please Do Now: What molecule does woody plant tissue have, that green plant tissue like leaves does not?Slide2
AgendaDo Now
Tree Notes
Tree
ring
activity
Spongy Mesophyll under the microscope
QuizSlide3
Why does lignin make wood woody?
Lignin is a large complex molecule
It has lots of strength in compression (it resists squeezing) where cellulose has lots of strength in tension (pulling)Slide4
Why does lignin make wood woody?
Lignin is even harder to digest than cellulose
So, not only does lignin give wood its rigidity, it also protects the tree from things that would like to eat it
Different species of trees have wood with different qualities because they have different amount of cellulose,
hemicellulose
and lignin in themSlide5
What is bark?Slide6
LigninBark cells also have lignified secondary cell walls, which is what gives bark its tough qualitiesSlide7
Tree TrunksTaking a cross section of a tree will show you multiple layers
Each of these layers has a different function, and a different structure to match that functionSlide8
What does the bark do?
It serves to protect the more valuable parts inside the tree from drying out, insects, disease, fire etc…
In most trees, it is made of very tough cells with lots of lignin in their secondary cell wallsSlide9
BarkSlide10
What does the phloem do?
It is what sugars move through when they are transported from the leaves where they are made down to the roots
It is a thin layer with lots of tube-like structures responsible for transportSlide11
PhloemSlide12
What is the cambium?
The cambium is where all the outward growth takes place
If the cambium gets damaged, the tree will dieSlide13
What is the sapwood?
The next layer in is the sapwood, the first layer that seems truly woody
It is still alive (unlike the heartwood)
It contains the xylem, which water is transported through
The cell walls here have lots of lignin, as well as lots of tube structures for water transportSlide14
SapwoodSlide15
What is the heartwood?
The heartwood is the center of the tree
The cells here are dead, and the material is basically all highly lignified cell walls
It provides structural support to the treeSlide16
Tree ringsSlide17
Tree ringsEvery year, a tree has periods when it is growing very fast (summer) and when it hardly grows at all (winter).
The periods when the cambium is dividing rapidly will produce a slightly different color of wood then when it is growing slowly
In this way “rings” form in the trunk, each representing a year of growth