Lecture 5 -- Plants Flashcards
what does secondary growth occur in
only in conifers and woody eudicots, no monocots are woody.
what does secondary growth produce
wood and bark
what does primary growth occur in
all vascular plants: ferns and seed plants
how does secondary growth originate: what causes it
ring around separation of primary xylem and phloem, this is called the vascular cambium
secondary xylem what is it made by, location, what it is
made by vascular cambium, to the inside of it, and is the wood in conifers and woody eudicots
secondary phloem, made by what, location, function
made by vascular cambium, located on the outside of the vascular cambium, and takes over the transport of sugar
cork cambium, role and location
forms outside of the secondary phloem, it protects plant – adds secondary dermal tissue – new protective layer called periderm which is known as the bark.
vascular cambium, primary function
makes secondary xylem and phloem, an produces rays.
amount of xylem produced vs phloem
more xylem is produced, – plant gets bigger in diameter by adding more xylem
rays
parenchyma, transports minerals in and out of diameter
fusiform initials
cells in vascular cambium – tracheids and vessels (xylem) sleeve elements (phloem)
ray initials
rays in both xylem and phloem
WOOD
secondary xylem lignin in secondary walls of tracheids and vessel elements
heartwood
dark xylem, aged wood, less punctual, and dark to help prevent rotting
sapwood
younger xylem, lighter in colour
growth rings
annual rings of xylem, live in environments with different seasons, exists because of difference in diameter of cells produced in secondary xylem at different times of the year.
label 3 year old woods stem.
3 rings of xylem, 1 ring of phloem, and 1 ring of cork. the line between the last ring of xylem and ring of phloem is the vascular cambium, the line between the phloem and the cork is the cork cambium. within the xylem rings, cells are often bigger at start of ring and start to get smaller towards end of ring
periderm in 3 layers
phelloderm (inside the cork itself), cork to outside, and cork cambium – these protect woody plants
anatomy of trunk
small circle, medium circle, and large circle, within each other. smallest – inside it is the xylem/wood,
medium – inside that is the phloem,
big – inside that is the cork.
line between small and medium is the vascular cambium
line between medium and big is cork cambium
cork + cork cambium from tree trunk =
periderm / bark
tissues of woody stem time table/ steps
apical meristem, primary meristem, primary tissues, lateral meristem, secondary tissues
apical meristem: protoderm, pro cambium, ground meristem (these are the primary meristems)
protoderm – epidermis
pro cambium – primary xylem and phloem
ground meristem – ground tissue (pith and cortex) (these are the primary tissues)
line between primary xylem and phloem – vascular cambium
context – cork cambium (these two are the lateral meristems)
vascular cambium – rays and secondary xylem + phloem, cork cambium – cork (both cork C and cork form periderm) (these are the secondary tissues)
transport: laws
movement of fluid in plants follow 2nd law of thermodynamics. – spontaneous
examples of transport
osmosis, diffusion, differences in pressure.
Water flows from what to what
more watery areas to less watery places
energy naturally tends to do what
spread out rather than stay concentrated in one place
disorder of water always goes what direction
up
sample overview of water flow
enters through roots, moves up the stem, and out the leaves
loss of water from leaves is what
transpiration
water enters the plant and moves along plant in three different routes, what are they
apoplastic, symplastic, and transmembrane route.
apoplastic
within cell walls, in between both cell walls and membrane.
symplastic
fluids move through the plasmodesmata
transmembrane
a mixture of both routes
cell compartments with three routes
draw three cells and each route.
cellulose is highly attractive to what
water – it is hydrophilic and absorbent
process of water movement follows what
process of water potential energy,
potential refers to :
as waters capacity to perform work
water flow relative to water potential
flows from regions with higher water potential (less negative) to lower water potential (more negative) totally water potential = potential of solutes + potential of pressure
water potential of a region wit solutes
water potential of a region with solutes is lower than a region without solutes
draw the 4 pictures representing water potentials with the two components solute and pressure
one with just solute, water should be flowing right, one with positive pressure water should flow left, one with both, water is at equilibrium, and last one with negative pressure, water is flowing right
what does the term plasmolysis mean
loss of water from cell by osmosis. cell membrane separates from cell wall
initial flaccid cell with solute potential of -0.7 what happens if put in sugar solution? in pure water?
sugar solution: the solute potential of sugar solution is -0.9 therefore has LESS potential that cell, that means that water will flow OUT of cell to lower potential. – cell shrinks
pue water: pure water has potential of 0, so -0.7 is LESS than pure water. therefore because of higher potential in water than in cell, water will flow INTO cell, enlarging it, the cell membrane is now pushing against cell wall – turgid (swollen due to pressure)
water moves spontaneously from higher to Lower water potential true or false
true
what way to water and minerals travel
upward ; tracheids in all vascular plants, and vessels in flowering
where does the ascent of sap occur
in xylem
what does herbaceous mean
non woods mature eudicot, root
water enters what
root, lateral transport of H2O and mineral;s
what two roots does water transport by
apoplectic and symplastic
steps of water flow
water flows into root hair, because water potential is less inside the root hair than outside. - then the water travels toward the stele, and encounters the special layer (endodermis)
- the endodermis has wax in its cell wall;s called Suberin.
- this Suberin makes casparian strips which is a barrier preventing molecules from passing
- the water will get stopped by the casparian strip if flowing though the apoplectic route.
- it gets shunted around therefore has to go through the cell membrane to get into the vascular tissues
- the cell membrane controls the amount of water and minerals;s that enters the cell
what are plant roots associated with
fungus – mycorrihizahe
what does mycorrhizae mean
“myco” = fungus “ rrhizae “ = roots
what does mycorrhizae do
increases surface area and aids absorption of minerals
benefits for both fungus and plants
fungus: gets photosynthetic products esp. sugar
plants: gets increase of ions – uptake in minerals
pathway of water simplified
- enters through soil
- goes through root hair, or mycorrhizae1
- to cortex
- through endodermis
- to xylem
- into atmosphere.
this happens naturally. – IS PASSIVE
how do water and minerals MOVE UP A PLANT
transpiration-cohesion-tension mechanism
transpirational pull
in leaves there is a pull of water, as water leaves the plant through an opening in the leaf (stomate) this pulls water up through the plant (like a rope)
why is water being pulled up through the plant
because water is being lost by the leaf
water flow in xylem step by step (transpiration-cohesion-tension mechanism)
- water evaporates from moist cells in. leaf stomates – transpiration (because atmosphere has low water potential therefore high –> low)
- water potential is lowered at air-water interface, causing negative pressure (tension) in xylem.
– hydrogen bonds hold water molecules together, (cohesion)
– xylem is UNDER TENSION GRADIENT so negative pressure at the top, and positive pressure at the bottom, therefore water will flow from bottom to up.
THIS IS A PASSIVE PROCESS
control of transpiration by stomates: cues to open at dawn:
light, CO2 depletion, and circadian rhythm – when filled with fluid they open, water / gasses can flow in and out
dry conditions; stomates
closure (to prevent water loss)
abscisic acid is a hormone that causes K+ to leave guard cells and that stimulates the closure.
somtate = what
2 guard cells
states of guard cells – open and closed whennn:
open when cells are turgid (swollen bc of + pressure)
closed when cells are flaccid – lost + pressure
