lecture 5 Flashcards
the meristem that is the youngest and most external part of the root
protoderm
: Cells produced by the protoderm that die and form a protective barrier on the tip of the root, so the delicate root tissue inside is not damaged when the root pushes deeper into the ground
the root cap
An intermediate meristem produced by the root apical meristem; located right behind the root apical meristem.
the procambium`
he tissue in the center of a young root
the steele
the tissue in between the procambium, protoderm, and root apical meristem
the ground meristem
The 3 Root growth zones
Zone of cell division
Zone of elongation
Zone of maturation
Where some of the root growth happens
Cell division only happens to the youngest cells
Closest to tip, closest to root apical meristem
cell division growth xone
Older cells that have stopped dividing
Where the majority of root growth happens
elongation growth zone
The oldest root cells
Have stopped dividing and elongating
Epidermal cells that make root hairs
Uses root hairs to absorb water
maturation growth zone
: a single epidermal cell that sticks out into the soil; Function to absorb water; increase surface area
root hairs
Series of events when roots make branched roots
- Needs to send out a side shoot from just inside the vascular cylinder because that’s how the stream of vascular tissue remains continuous
- The root branch has all the parts the original or main root has, apical meristem, all the intermediate meristems and all the parts of root growth
single layer of cells that contains the steele (vascular tissue); occurs in both eudicots and monocots
endodermis
center of eudicot root; surrounded by endodermis
vascular cylinder
the center ground tissue in monocots
pith
is the set of cells where a lateral root can begin; located inside steele and endodermis
paracycle
The two new meristems of secondary growth (lateral meristems/ secondary meristems)
vascular cambium
cork cambium
One of the two meristems that make bark and wood. The meristem that is made first
vascular cambium
meristem that is formed in the middle of the vascular bundles
vascular cambium
What side is the primary phloem and primary xylem of the vascular cambium?
primary phloem on outside of vascular cambium
primary xylem on inside of vascular cambium
What is the secondary xylem?
wood
what is outside the secondary phloem?
bark
What is the function of the vascular cambium?
to make secondary xylem and secondary phloem
Is wood on the outside or inside of vascular cambium?
inside because its the secondary xylem
The two cells of the vascular cambium?
ray initials
fusiform initials
What direction do the rays, the ray initials make, run in?
laterally in the stem
Why do the rays run laterally?
allows the plant to move things laterally; get stuff out
What do fusiform initials make?
xylem and phloem tissue
what shape are fusiform initials?
tapered
What elements are inside the vascular cambium?
secondary xylem: wood
growth rings
rays
polymer that makes wood “woody”; inside the secondary walls of tracheids and vessel elements; second most abundant polymer in the world; only natural polymer in plants not made of sugars
lignin
The dark middle of wood.
heartwood
why is heartwood dark
.The oldest parts get toxic, wasted materials that turns the wood dark. These toxic materials are thought to help prevent rotting of the center
The light part of wood?
sapwood
where does the most fluid flow in wood occur? sapwood or hardwood?
Most active spot for fluid flow occurs in sapwood; most water flowing up trunk occurs in sapwood, not hardwood
When are the biggest secondary xylem cells made?
spring
when are the smallest secondary xylem cells made?
winter
Why do secondary xylem cells vary in size?
their rate of production varies
what happens to the primary parts of the plant?
they disappear after a period of time, because there is nothing there to make them anymore
what happens to the epidermal cells after the plant becomes woody?
they aren’t there, nothing to protect the plant… cork cambium steps in
Made by cylinder of cortex cells outside the vascular cambium
cork cambium
what is the cork cambium’s job?
to produce periderm
What is periderm?
phelloderm and cork
thin layer of living parenchymal cells
to the inside (some woody species)
phelloderm
suberized (wax in the cell walls), dead cells
To the outside
Protects woody plants since there is no more epidermis
cork
cork is impervious to ____
liquid
xylem flow goes in what direction?
upwards only
phloem flow goes in what direction
multiple directios
liberation of O2 and intake of CO2
photosynthesis
liberation of CO2 and intake of O2 in roots; why does this happen?
root respiration; roots are not photosynthetic
The three cell components discussed
3 cell components:
1) Cytosol: everything inside cell membrane that is not an organelle
2) Vacuole: organelle for storage
3) Cell wall
transport route inside cell body itself.
symplastic; plastic means plasma membrane
route of transport outside cell membrane, in the cell wall,
apoplastic; “apo” means away from
route of transport; combo of symplastic and apoplastic; water is inside and outside cell at various times
transmembrane
fluid flows spontaneously from higher to lower energy
2nd law of thermodynamics
energy difference in water, energy that drives spontaneous movement of water
water potential
filling a balloon is an example of ___ pressure
positive
drawing fluid from a water balloon is an example of ____ pressure
negative
Psi (Ψ): symbol for what
water potential
loss of water due to osmosis
plasmolysis
plump cell with water
turgid
water and minerals; materials inside xylem
sap
non-woody mature eudicot root
herbaceous
path of xylem
soil→ root→ shoot→ leaf→ atmosphere
single ring of cells that functions as a checkpoint for the plant to say who it allows in. Has in its walls a waxy material called casparian strip
endodermis
- waxy material inside the cell walls of the endodermis
- where primary wall and middle lamella used to be
- Waterproof and impermeable to ions: suberin
casparian strip
function of endodermis (and casparian strip)?
Does not permit fluid to pass through it unless that fluid goes into the cell membrane.
–> The symplastic route continues going through the cells
But the Apoplastic route going outside the cell membranes hits the waxy part of the endodermis (the casparian strip) and is now forced to change and go through the cell membrane otherwise the fluid won’t be allowed to continue into the plant
What is the point of an endodermis?
The cells force the fluid to go through cell membrane because it can then sort what the plant actually needs to allow to go through and what the plant doesn’t want allowed in
contents within endodermis
Cylinder : one cell thick Steele: everything inside the endodermis Xylem and phloem Pith Pericycle (origin of lateral roots)
waterproof cells that fill the periderm; cells that have wax filled in their cell walls
cork
everything outside secondary phloem
bark
wood
second xylem
made by cork cambium; filled with waterproof cells called cork
periderm
