Water-Plant Relations (Exam 2)

Question 1

water is the

Answer 1

universal solvent

Question 2

why is water the universal solvent?

& therefore (2)

Answer 2

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)

Question 3

what explains water movement through X?

Answer 3

tensile strength

Question 4

what leads to tensile strength

Answer 4

cohesion

Question 5

cohesion =

Answer 5

water liking itself

Question 6

adhesion =

Answer 6

water liking others

Question 7

water moves from

Answer 7

a higher potential energy to a lower potential energy

Question 8

water moves… (2)

Answer 8

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

Question 9

water potential aka

Answer 9

“U”

Question 10

water movement depends on

Answer 10

overall water potential (U) energy

U in water > U in air

Question 11

water potential energy (U) is usually measured in

Answer 11

units of pressure

Question 12

units of pressure we saw

Answer 12

• Bars (1 bar = 14.5 psi)

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

Question 13

plant cell pressure is measured in

Answer 13

MPa (megapascals)

Question 14

components for liquid water (4)

Answer 14

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)

Question 15

Π (Osmotic Pressure) eqtn

Answer 15

Π = RT(Ec)
E = sigma

Question 16

as solute conc increases (2)

Answer 16

• Π (Osmotic Pressure) increases

- U (water potential energy) decreases

Question 17

in trees, P =

Answer 17

(-)

this is why trees don’t bleed

Question 18

clay soil…

small particles

Answer 18

“holds” H2O best

Question 19

sandy soil…

big particles

Answer 19

“drains” H2O best

Question 20

Ψsoil vs Ψroot

Answer 20

Ψsoil > Ψroot (for root to take up H20)

Question 21

Water potential energy (U) equation

Answer 21

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

Question 22

P increases with

Answer 22

depth

Question 23

how does water move up the plant?

Answer 23

plants let physics do the dirty work

Question 24

from leaves, water…

Answer 24

evaporates

Question 25

why does water evaporate from the leaf?

Answer 25

humidity in the leaf almost = 100% | air is rarely over 50%

Question 26

stomata on leaves open for | therefore

Answer 26

CO2 uptake, | therefore water loss in inevitable

Question 27

in the xylem, water exists as

Answer 27

a column

Question 28

tensile strength (due to cohesion) of water allows...

Answer 28

...water to be "pulled" up the plant through the X

Question 29

what happens when transpiration > supply?

Answer 29

= cavitation

Question 30

soil consists of

Answer 30

particles & open spaces (pores)

Question 31

soil pores are typically occupied by | which has

Answer 31

air & water, | which has dissolved inorganic nutrients

Question 32

availability of water in soil depends on

Answer 32

the interactions of water with the soil

Question 33

(availability of water) sand...

Answer 33

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

Question 34

(availability of water) clay...

Answer 34

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

Question 35

what determines the water potential in soil? | unless...

Answer 35

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

Question 36

soil water =

Answer 36

hygroscopic (solid particles)

Question 37

roots take up

Answer 37

capillary water

Question 38

field capacity =

Answer 38

max amount of water held by soil

Question 39

roots take up most of their water through | &...

Answer 39

root hairs | & mycorrhizae can take up water too

Question 40

can leaves take up water?

Answer 40

yes, through fog

Question 41

water is not

Answer 41

actively absorbed | which means no energy is expended

Question 42

water moves into the plant if...

Answer 42

Ψsoil > Ψroot

Question 43

when Ψsoil < Ψroot

Answer 43

water can actually flow out of the plant | usually changes in the root prevent this

Question 44

how do roots prevent water form flowing out of it

Answer 44

casparian strip kill cortex lignify epidermis

Question 45

water in the X is

Answer 45

"pulled"

Question 46

water that evaporates is

Answer 46

replaced on cell walls

Question 47

what allows water to be pulled?

Answer 47

the cohesive properties of water | tension

Question 48

tension =

Answer 48

(-) hydrostatic pressure

Question 49

the theory of water movement in plants =

Answer 49

evaporation-cohesion-tension theory