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BOT 201 > Water-Plant Relations (Exam 2) > Flashcards

Water-Plant Relations (Exam 2) Flashcards

1
Q

water is the

A

universal solvent

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2
Q

why is water the universal solvent?

& therefore (2)

A

bc water is polar
& therefore has partial charges (no net charges) (solvent for other polar molecules & ions)
& allows for hydrogen bonding (approx 4 kJ/mol) (tensile strength)

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3
Q

what explains water movement through X?

A

tensile strength

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4
Q

what leads to tensile strength

A

cohesion

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5
Q

cohesion =

A

water liking itself

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6
Q

adhesion =

A

water liking others

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7
Q

water moves from

A

a higher potential energy to a lower potential energy

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8
Q

water moves… (2)

A
  • downhill w/ gravity
    (U = mgh)
  • “up” from bodies of water
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9
Q

water potential aka

A

“U”

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10
Q

water movement depends on

A

overall water potential (U) energy

U in water > U in air

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11
Q

water potential energy (U) is usually measured in

A

units of pressure

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12
Q

units of pressure we saw

A
  • Bars (1 bar = 14.5 psi)

- MPa (megapascals) (1 MPa = 10 bar)

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13
Q

plant cell pressure is measured in

A

MPa (megapascals)

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14
Q

components for liquid water (4)

A
  1. ) H = Hydrostatic Pressure (P)
  2. ) Π = Osmotic Pressure (solutes)
  3. ) ρ(of w)gh = Pressure due to gravity
  4. ) Matric pressure (H2O interactions with surfaces)
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15
Q

Π (Osmotic Pressure) eqtn

A 
Π = RT(Ec)
E = sigma
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16
Q

as solute conc increases (2)

A
  • Π (Osmotic Pressure) increases

- U (water potential energy) decreases

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17
Q

in trees, P =

A

(-)

this is why trees don’t bleed

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18
Q

clay soil…

small particles

A

“holds” H2O best

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19
Q

sandy soil…

big particles

A

“drains” H2O best

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20
Q

Ψsoil vs Ψroot

A

Ψsoil > Ψroot (for root to take up H20)

21
Q

Water potential energy (U) equation

A

Ψ = P - Π + ρ(of w)gh + Matric Pressure

22
Q

P increases with

A

depth

23
Q

how does water move up the plant?

A

plants let physics do the dirty work

24
Q

from leaves, water…

A

evaporates

25
Q

why does water evaporate from the leaf?

A

humidity in the leaf almost = 100%

air is rarely over 50%

26
Q

stomata on leaves open for

therefore

A

CO2 uptake,

therefore water loss in inevitable

27
Q

in the xylem, water exists as

A

a column

28
Q

tensile strength (due to cohesion) of water allows…

A

…water to be “pulled” up the plant through the X

29
Q

what happens when transpiration > supply?

A

= cavitation

30
Q

soil consists of

A

particles & open spaces (pores)

31
Q

soil pores are typically occupied by

which has

A

air & water,

which has dissolved inorganic nutrients

32
Q

availability of water in soil depends on

A

the interactions of water with the soil

33
Q

(availability of water) sand…

A

…dries quickly, but when wet, most of the water is available to the plant

34
Q

(availability of water) clay…

A

…holds water longer, but less of the water is available to the plant

35
Q

what determines the water potential in soil?

unless…

A

hydrostatic pressure & interactions with the surfaces (matrix pressure) determine water potential (Ψ/U) more than solutes (unless soil has very high concentrations of salts)

36
Q

soil water =

A

hygroscopic (solid particles)

37
Q

roots take up

A

capillary water

38
Q

field capacity =

A

max amount of water held by soil

39
Q

roots take up most of their water through

&…

A

root hairs

& mycorrhizae can take up water too

40
Q

can leaves take up water?

A

yes, through fog

41
Q

water is not

A

actively absorbed

which means no energy is expended

42
Q

water moves into the plant if…

A

Ψsoil > Ψroot

43
Q

when Ψsoil < Ψroot

A

water can actually flow out of the plant

usually changes in the root prevent this

44
Q

how do roots prevent water form flowing out of it

A

casparian strip
kill cortex
lignify epidermis

45
Q

water in the X is

A

“pulled”

46
Q

water that evaporates is

A

replaced on cell walls

47
Q

what allows water to be pulled?

A

the cohesive properties of water

tension

48
Q

tension =

A

(-) hydrostatic pressure

49
Q

the theory of water movement in plants =

A

evaporation-cohesion-tension theory

BOT 201 (26 decks)

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