Lecture 6 Flashcards
In any region, water energy is the SUM of the:
Solute (osmotic) potential energy (0 or negative)
Pressure potential energy (any value, negative, positive or 0)
process of: Water evaporates from moist cells (like how clothing dries on clothes line outside, will dry down to level of atmosphere) in leaf stomatal
transpiration
Water potential is lowered (because water is being pulled out like a rope) at air-water interface; causing negative pressure in xylem
tension
Hydrogen bonds hold water molecules together
cohension
Xylem under tension gradient: pressure potential _____at top, _____ as you go down the plant
negative, getting more positive as you go down the plant
Water and minerals enter roots by osmosis because….
there is higher solute concentration inside plant than in soil
special cells that open and close to allow for the exchange of gases
guard cells
Gas exchange couldn’t happen through the cell wall of land plants because of _________
the waxy cuticle
type of cell?
Have microfibrils oriented transversally
When cell swells (turchid; filled with water) it causes opening
Create an opening, the inside (the stomata)
guard cell
How does the plant open and close the guard cells?
Pumping potassium ions
How To open guard cells
The plant pumps K ions into cell Solute potential, osmotic potential, goes down Water enters spontaneously Guard cells swell Stoma is open
what is conducted by abscisic acid
the closing of guard cells
the process of closing guard cells
Conducted by abscisic acid
Abscisic acid tells K ions to leave guard cells
Water leaves guard cells once solute is out of guard cells
Guard cells close
No access to stoma
cues for plant to open stomata at dawn?
Light
CO2 depletion
Circadian rhythms
what does the plant do in dry conditions to avoid water loss? How do they do this?
Abscisic acid (hormone)
Causes K positive to leave guard cells
Stimulates stomata closure
phloem transport, passive or active?
active
method of phloem transport?
bulk flow
: extra cells, parts of the phloem; type of parenchyma cells; actively pump sugar water
companion cells
companion cell that is where water starts
source cell
companion cell where water ends up
sink cell
what does Sucrose being pumped by source cell goes into sieve tube do to the osmotic potential?
osmotic potential goes down; more negative
What happens to the top of the tube if the osmotic potential is down due to sucrose having been just pumped into it?
water rushes in to balance out the sucrose molecules; water flows into the sieve tube
where does the water that rushes into the sieve tube when osmotic potential is down come from?
xylem tube next to it
what happens to the pressure of the sieve tube in the top area where water and sucrose was just pumped into?
the pressure goes up