Exam 2 Flashcards
How can plants absorb water?
roots, leaves, and as vapor through pores
Properties of water that allow transport within a plant
cohesion, adhesion, surface tension
How can cells alter their solute potential?
- active transport of solutes across the membrane
- break down reserved starches into glucose
When does the radius of curvature decrease?
when water recedes into cell wall spaces
Osmosis
movement of water across a selectively permeable membrane
Solute potential is also known as…
osmotic potential
Pressure potential is usually positive in ______ and negative in __________.
positive in cells and negative in xylem
Tracheids
- long, slender xylem
- lateral movement of water through pit pairs
vessel elements
- short, wide xylem
- vertical movement of water through sieve plates
guttation
when pressure builds in the roots and sap is pushed up through the plant to the leaves, where it escapes through pores
hylathodes
pores present along leaf margins that don’t have guard cells
cohesion-tension theory
negative pressure develops in the leaves as water evaporates, and that tension pulls water through the xylem
apoplastic pathway
water travels through the root cortex to the xylem via the apoplastic space, never entering cells
symplastic pathway
water travels through the root cortex by going cell to cell via plasmodesmata
endodermis
protective layer of cells around the vascular tissue with selectively permeable membranes
casparian strip
lignin and suberin deposits that prevent apoplastic movement
field capacity
the amount of water that soil can hold after it has been saturated and drained (-0.03 MPa)
permanent wilting point
when water begins to bind so tightly to soil particles that it is no longer accessible to plants (-1.5 MPa)
plant available water
the range between field capacity and permanent wilting point where plants can access water without the soil being saturated
formula for water potential
Ψ water = Ψ solute + Ψ pressure + Ψ gravity
formula for solute potential
Ψ solute = -RTc (
R = gas constant
T = temp
c = concentration
formula for negative pressure caused by water adhesion to cell walls
P = -2Tcos(a) / r
r = radius of curvature
T = surface tension
formula for water vapor potential
Ψ wv = 0.46 x T x ln [%RH/100]
T = temp
cytoplasmic sleeve
extension of cytoplasm from one cell to another
