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BIOL 331 > Intro > Flashcards

Intro Flashcards

1
Q

3What is the four step movement of water in plants?

A
  1. Water moves from soil into the root
  2. water moves through the root
  3. water moves up through the xylem
  4. water moves from leaf to air
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2
Q

How is water moved through a plant, what does it require?

A

water is pulled upwards by transpiration from leaves - so water movement requires leaves exposed to air

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3
Q

5 important properties of water

A

Water is cohesive - sticks to itself
Water is an excellent solvent
Water can dissociate into ions
has high latent heat of vaporization - means it is thermodynamically stable
water has a high tensile strength

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4
Q

Three specific properties of water that make transpiration possible?

A

cohesion - water sticks to itself
adhesion-water sticks to other substances - cell walls of xylem
surface tension - property of liquid surfaces which allows it to resist an external force due to the cohesive nature of its molecules

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5
Q

Another name for the process of plants bringing water from roots to shoots is called?

A

Capillary action

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6
Q

What is water potential in plants?

A

Movement of the potential energy of water - water moves from places of high potential energy to areas of low potential energy

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7
Q

What are the three major factors affecting the water potential in plants?

A

Concentration- solute potential
Pressure potential
Gravity potential

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8
Q

Why is water potential important?

A

Because it regulated cell growth, photosynthesis and crop productivity

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9
Q

What is the definition of water potential?

A

the ability of water molecule to move freely in a solution

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10
Q

Solute potential Ws is defined by what?

A

Gas constant, temperature in K and solute concentration in mol/L
- also needs the ionization constant if ions existed - ie NaCl
- sugar does not ionize so therefore the constant is 1
- NaCl goes to Na+ and Cl- which makes it 2
therefore the system has an ionization constant of 3

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11
Q

Pressure potential Wp is determined by what?

A

turgor pressure and tension - turgor pressure increases hydrostatic pressure and tension is a decrease in it.

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12
Q

Gravity potential Wg is determined by what?

A

water density (constant ish), gravitational constant, height of water above the ground
- results in the unit of pressure

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13
Q

What thermodynamic component of Ww is responsible for water movement?

A

Osmosis or Ws

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14
Q

solute potential is the same as…

A

osmotic potential

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15
Q

the solute potential is always ___ when solutes are added to eh system?

A

reduced because there is a negative sign on the equation
- all water systems have some amount of solutes

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16
Q

Define osmosis

A

phenomenon of water flowing across a semi permeable membrane from areas of low solute concentration to areas of high solute concentration
- water moves to where the stuff is to balance it out

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17
Q

Water moves from areas of high water potential to areas of low water potential, explain how osmosis works with all the math shit

A

In a system with pure water and water with surcrose
- gravity constant will be ignored
- the system of pure water will have a Ww of 0
- the system with sucrose will have a negative Ws because of -RTC
- therefore the side with sucrose will have a lower total water potential than the side of just pure water - water moved towards the side with sucrose

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18
Q

What value will change to balance Ws or solute potential?

A

pressure potential Wp - turgor pressure builds up to balance in cells - or plants use solutes to regulate turgor pressure

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19
Q

What is the purpose of a plant cell wall?

A

Resistance of the cell to deformation - the wall is rigid to provide structural support and to prevent osmotic lysis by turgor pressure

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20
Q

Water limitation does what to turgor pressure?

A

lowers turgor pressure

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21
Q

If solute concentration is higher outside the cell than inside the cell, what happens and what is it called?

A

Water will leave the cell, the cell is plasmolyzed and the inside of the cell is hypotonic and the outside is hypertonic

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22
Q

If solute concentration is higher inside the cell than outside, what happens and what is it called?

A

water will enter the cell, the cell is turgid and the inside of the cell is hypertonic and the outside is hypotonic

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23
Q

How do water molecules move between plant cell membranes?

A

Through water specific channels called aquaporins

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24
Q

Why is solute potential negative?

A

Because water will form hydrogen bonds with the solute meaning the energy of the water molecule is tied up with the dissolved solute - therefore there is less potential energy in the water molecules

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25
Q

A system is in equilibrium when…

A

the pressure potential is the inverse of the solute potential
Wp = -Ws

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26
Q

If the solute potential inside the cell is greater than the solute potential outside the cell (i.e, a smaller negative number) what happens to the cell?

A

the cell is plasmolyzed and water leaves the cell
- greater solute potential means less solute, water moves to where there is more solute - so would move out of the cell

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27
Q

What is the structure of an aquaporin?

A

tetrameric arrangement - each monomer forms a water channel - so four channels per aquaporin
- Has an NPA structure - asparagine - proline - alanine
- Asparagine has an NH4+ structure and the slight positive change can pull on the slight negative charge on water

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28
Q

What two things regulate aquaporin channel activity?

A

phosphorylation and ph control
Under standard conditions aquaporin protein is phosphorylated adn active
under drought conditions aquaporin protein is dephosphorylated and inactive
Under high water conditions the pH drops which will close the aquaporin

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29
Q

All change in water potential begins with ____

A

surface tension

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30
Q

Define transpiration

A

evaporation of water mainly through the stomata of leaves

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31
Q

Plant cells become turgid when you put them in pure water. This is because the water potential in the plant cells is lower than the pure water. Is this correct or incorrect?

A

Yes, water always moves from areas of high water potential to areas of low water potential.
Solutes are in plant cells but not in water, higher solute means a more negative solute potential - brings the water potential down.

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32
Q

An increase in solute concentration means a _____ in solute potential

A

decrease

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33
Q

How do you effectively stop osmosis?

A

with pressure - the pressure potential will always balance the solute potential.

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34
Q

What is Ficks law?

A

describes the movement of water by diffusion
dm/dt = -D A (dc/dx)

dm/dt = amount of substance moved per unit time
D = diffusion coefficient
A = area where flow passes through
dc/dx = gradient of concentration (change in concentration per unit distance in a direction perpendicular to the plane A)

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35
Q

Which thermodynamic component does a plant cell use to drive water movement?

A

solute potential somehow

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36
Q

How do plants create the thermodynamic gradient that drives water movement through the plant?

A

transpiration

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37
Q

Which type of mesophyll cells is important for driving water movement

A

spongy mesophyll cells because they have air gaps that help drive transpiration

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38
Q

Diffusion is faster according to Ficks law when -

A

the concentration gradient (dc/dx) is steeper
the area (A) is larger
the distance (x) is smaller
D is larger

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39
Q

What are the top and bottom sides of the leaf called?

A

Adaxial - top
Abaxial - bottom

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40
Q

explain the relationship between evaporation and condensation in relation to the stoma being open or closed

A

when the stoma is closed evaportation and condensation are equal
- but when the stoma is open the surface tension is increased (?) and evaporation is greater than condensation so there is a net loss of water from the system

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41
Q

structural sugars in the cell wall provide sites for _________ to water molecules

A

hydrogen bonding sites

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42
Q

4 steps to generating transpirational pull in leaves

A
  • water vapor diffuses from the air space of the leaf to air outside through stomata in transpiration
  • the water vapor lost by transpiration is replaced by evaporation from the water film that coats mesophyll cells
  • water vapor diffuses from the air space of the leaf to air outside through stomata in transpiration
  • evaporation causes the air water interface to retreat further into the cell wall and become more curved as the rate of transpiration increases – diagram with the circles
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43
Q

what is the relationship between the radius of the curvature of the air water interface and the resulting hydrostatic pressure?

A

As the radius of the curvature decreases, so does the hydrostatic pressure - gets more negative
- infer that greater curvature is greater displacement (bouncier trampoline) so therefore the force generated is stronger

  • decreased hydrostatic pressure means increased surface tension
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44
Q

Evaporation results in the air water interface to recede towards outer cellulose microfibrils of the cell wall and then _________ (POLLEV)

A

Surface tension can be built up at the air water interface

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45
Q

what is the gradient of water potential throughout the plant system?

A

high water potential is closer to the xylem and low water potential close to the stomata

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46
Q

Why is there less water vapor / evaporation close to the xylem

A

because there is less airspace

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47
Q

____ evaporation = ____ surface tension = _____ hydrostatic pressure

A

more evaporation = more surface tension = less hydrostatic pressure

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48
Q

3 pathways for water flow

A

Apoplasmic pathway - water moves through the intercellular spaces - cell walls - no entry into cells

Symplasmic pathway - water moves into cells via plasmodesmata

Transcellular pathway - water moves across plasma membranes - both between cells and in central vacuole

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49
Q

Three metrics that determine amount of water flow in each pathway

A
  • magnitude of water potential gradient
  • tissue capacitance
  • resistance to water flow (hydraulic resistance)
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50
Q

7 step process for water movement through the leaf?

A
  1. stomata open
  2. water vapor diffuses from internal air space, down concentration gradient, into the air
  3. net loss of water vapor causes air water interface to recede towards outer microfibrils
    4.establishment of the water potential gradient begins when the air water interface touches outer microfibrils
  4. H bonding / cohesion transmits tension at surface to bulk water movement
  5. time dependent buildup of surface tension
  6. water pulled towards air water interface
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51
Q

Which pathway for water movement has basically 0 hydraulic resistance?

A

apoplasmic because water does not have to cross a membrane

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52
Q

define plasmodesmata

A

microchannel connecting between plant cells through the cell wall

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53
Q

In plant leaves, can the water potential gradient be developed between xylem and spongy mesophyll cells due to different evaporation rates?

A

yes it can - evaporation rates are higher by the stomata than at the xylem because of the inter air spaces

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54
Q

How do plants create the thermodynamic gradient that drives water movement through plant - what is the rate of water loss equal to?

A

evaporation rate - rate of water loss from air water interface = rate of water delivery pulled from interior sources

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55
Q

are xylem cells dead?

A

mature xylem is dead but immature xylem is alive

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56
Q

explain tracheids

A
  • primitive water conducting elements
  • present in gymnosperms and angiosperms
  • cell size is species dependent
  • consists of long thin walls with tapered ends
  • ## reinforced with lignin
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57
Q

tracheids have a ____ _____ that allows for a low resistance pathway to be developed between neighboring tracheids

A

pit pair

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58
Q

Explain vessels

A
  • advanced water conducting elements
  • present only in angiosperms
  • one vessel contains n vessel elements
  • contain a perforation plate for bulk water flow
  • ## forms effectively a longer and wider tube than the tracheids
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59
Q

are wider water transport vessels better than narrower ones?

A

wider is more efficient at transporting more water and taking up less area - but not good under water stress and prone to xylem embolisms

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60
Q

Define cavitation

A

a condition where an air bubble moves into a vessel

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61
Q

Define an embolism

A

the blocking of a xylem vessel or tracheid by an air bubble or cavity

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62
Q

Why might it be important to have vessels and trachieds when discussing embolisms

A

while vessels can move significantly more water, embolisms can spread between vessels whereas they are confined to single celled trachieds

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63
Q

Cavitation results in the embolism in the xylem of vascular plants when water is pushed too strongly within the xylem. True or False?

A

False - drought is what causes xylem, when theres not a full stream of water and air bubbles will get in. if the stream of water is constant gaps will not appear

64
Q

How did we experimentally determine evidence for tension in the xylem?

A

You can measure the trunk diameter of a young tree and how it changes throughout the day - trunk shrinks in the day when transpiration and therefore tension is highest and xylem is pulled inwards under tension

65
Q

Three soil particle types and sizes

A

Sand - biggest
silt - middle
clay - smallest

66
Q

How does soil type affect water movement in said soil?

A

water moves through large particles like sand mainly by gravitational pull - will go down more than out

water moves through small particles like silt and clay primarily though capillary action - moves outwards significantly more and is slower to move donwards

67
Q

3 levels of water retension in soils? (FC)

A

Saturated - all pores are full of water and excess water is lost from gravity

Filled Capacity - there is available water for plant growth

Wilting point - no water available to plants - pores empty

68
Q

How is root architecture affected by water flow into roots

A

Under water stress or low rain , some root systems will not spend energy growing deep roots when plant is already water limited - will grow outwards instead of down

69
Q

Three pathways of water transport specifically in roots

A
  • Apoplasmic - movement through cell walls except when crossing endodermis
  • Symplasmic - movement through cytoplasm and plasmodesmata
  • Trancellular - water crosses plasma membrane and tonoplast in parallel with movement through plasmodesmata
70
Q

What is the Casparian strip?

A

specific section of endodermis called the Casparian strip
- a wall made of lignin on the outside of the cell walls - forces water to cross a plasma membrane to get around it

71
Q

How is root water transport different from shoot water transport?

A

Root water transport is done from positive pressure that forms as roots uptake water - water is pushed towards the shoots - compare to shoots where it is pulled via hydrostatic pressure

72
Q

What is suberin and where is it found?

A

Cell wall associated biopolymer found in the endodermis of roots
- mainly found in highly differentiated / mature root areas
- effectively a larger barrier surrounding the whole cell - stops water from entering endodermis by any means except a plasma membrane - must go into the symplastic route of a previous cell
- significantly decreases water permeability

73
Q

When can water in the roots move entirely in the apoplasmic pathway?

A
  • only in young undifferentiated roots
74
Q

Two kinds of conductance in roots?

A

Radial conductance - from soil to stele
– affected by anatomy, morphology etc - from outside to center of root

Axial conductance - from root to shoot through xylem
- affected by number, diameter, structure etc

75
Q

What is the critical soil water potential threshhold?

A

the point where most plants will alter physiology to respond to water stress by slowing photosynthesis and transpiration

  • varies by plant species/ individual genetics / environment etc
76
Q

Differences between sensitive and resilient plant responses to different speeds of water loss?

A

if water loss is slow enough most species can regulate correctly - but if water loss is fast, sensitive plants will suffer significantly more damage than resilient plants

77
Q

What is osmotic adjustment?

A

A lowering of solute potential (meaning an increase in solutes) due to net solute accumulate due to water stress. Solute concentration will rise which lowers the water potential meaning more water will hopefully go into the cells

78
Q

Are cell walls completely rigid?

A

No - elastic adjustment of the cell wall is the relationship between cell volume and turgor pressure - will temporarily soften cell wall to allow more water in and delay loss of turgor pressure under drought conditions

79
Q

Short term responses to water stress (4)

A
  • decrease stomatal conductance
  • alterations in hydraulic activity
  • osmotic adjustments
  • elastic adjustments
80
Q

long term responses to water stress (2)

A
  • introduction of drought induced genes
  • changes in growth rate including root architecture
81
Q

under water stress, resources will likely be allocated where?

A

to the root

82
Q

name three different root adaptations to water stress and what causes them

A

root adaptations determined by genotype and stress severity
- primary root elongation
- lateral root elongation
- short lived drought induced lateral roots

83
Q

Osmotic adjustment is defined as an increasing of osmotic potential due to net solute accumulation in response to drought stress —> true or false?

A

False, osmotic adjustment is a lowering of solute/osmotic potential not an increase

84
Q

Define osmotic adjustment

A

a lowering of solute / osmotic potential due to a net solute accumulation in response to drought stress
- solute potential decreases when solute concentration increases

85
Q

Three modes of energy exchange

A

convection - heat transfer through currents
conduction - heat transfer by molecules bumping into eachother
radiation - heat transfer by radiating outwards from heat source

86
Q

What is the relationship between wavelength, temperature and energy?

A

short wavelengths = high temp = high energy
long wavelengths = low temp = low energy

87
Q

What percent of sunlight is actually absorbed into plants?

A

around 50%

88
Q

what are the three different / type of energy inputs for plants?

A

Sun - short wavelengths directly from the sun
Soil - long wavelengths from reflected sunlight off the soil
Air - long wavelengths reradiated from the air

89
Q

Are plants efficient at storing energy?

A

not really - much of the large energy input is lost

90
Q

What percentage of the total energy input is re radiated out from leaves

A

around 70% of the total energy is reradiated out

91
Q

What percentage of the total energy input is lost through conduction and convection?

A

around 10% on simple oval shaped leaves - convection occurs via wind

92
Q

Under normal conditions what percent of the total energy input is lost via latent heat of vaporization?

A

around 20%

93
Q

In drought conditions, how does the energy input/ output model change?

A

Under normal conditions around 20% of energy is lost through the latent heat of vaporization but under drought conditions this value approaches zero (stomata close and transpiration stops)

94
Q

How does the energy release strategy change under drought?

A

because LE drops to zero, reradiation at the leaf surface increases along with the leaf surface temperature
- establishes new thermal eq at leaf surface
- increases reradation and conduction+convection energy release by some factor
- significantly affects photosynthesis

95
Q

What is the relationship between net photosynthesis and leaf temperature - under drought conditions

A
  • photosynthesis increases significantly under high light and higher leaf temperature - until the leaf temperature approaches 40C where photosynthesis plummets as the temp is too hot to be active
96
Q

Why are cactus spines mostly white?

A

white reflects light away which is important in the conditions cacti usually grow

97
Q

Definition of an essential plant element?

A

An element that is needed to completion of the life cycle - production of a viable seed

98
Q

93% of plant dry mass is composed of what 3 elements?

A

C, O, H
- input and products of photosynthesis (CO2, O2, H2O, C6H12O6`

99
Q

What is a mineral element, what are the two largest ones

A

other elements that are obtained from soils
- N and K play the largest role

100
Q

What are some environmental downsides to large scale fertilization?

A

eutrophication (increase in algae due to increased nutrients)
greenhouse gasses
nitrogen fixation is energy demanding
phosphate and potash mining is destructive

101
Q

Most fertilizers are known as ____ fertilizers

A

NPK fertilizers

102
Q

What are the plant primary macronutrients (3)

A

N, P, K

103
Q

What are the plant secondary macronutrients? (3)

A

Mg, S, Ca

104
Q

List 3 (/9) essential plant micronutrients

A

B, Cl, Na, Mn, Fe, Ni, Cu, Zn, Mo

105
Q

What is the law of the minimum

A

Idea of a limiting nutrient, if one growth factor is deficient plant growth will be limited by that nutrient even if all other factors are fine
- yield is proportional to the amount of the most limitng nutrient

106
Q

What are mobile and immobile nutrients - provide examples

A

Mobile nutrients can move throughout the plant, symptoms will show in the oldest leaves first - N P K Mg

Immobile nutrients will primarily affect the newest leaves - B, Ca, S

107
Q

What is the Hoagland nutrient solution?

A

modern recipie for strong fertilizer
- highest possible concentrations of nutrient elements without producing toxicity symptoms
- maintains pH
- maintains iron availibility

108
Q

Can plants grow in excess nutrients?

A

Yes, kinda
Once plant tissues reach a certain concentration of nutrients, the critical point is reached. Past this point excess nutrients do not increase plant growth, but plants can become saturated with nutrients without toxicity until a certain point, but it is a range

109
Q

What does a chelator do

A

helps maintain iron nutrient availability

110
Q

What is cation exchange capacity (CEC)?

A

The degree to which a soil can absorb and exchange ions
- cations dissolved in soil water bind to negatively charged soil particles
- higher CEC = more potential for minerals in soil
- positively charged nutrients are free to move in soil solution and available to plants
- plants secrete H+ to exchange with bound cations

111
Q

Why is pH an important factor of plant growth? What is the optimal pH range?

A

Optimal pH range 5.5-7.0 for nutrients - 6.8-7.2 ideal for most factors, 5.5-6.5 for roots
- important for nutrient availability, soil microbes and root growth
- bacteria are prevalent in alkaline soils and fungi are prevalent in acidic soils

112
Q

Which type of soil has the highest cation exchange capacity?

A

usually clay - but need to balance with water drainage ability of the soil

113
Q

Why is N an essential element?

A

important in amino acids and peptide bonds
essential structure of DNA and RNA

114
Q

Provide a brief summary of the Nitrogen cycle

A

Two sections - aerobic reactions and anaerobic reactions
Nitrate (NO3-) is reduced to Nitrite (NO2-), which undergoes denitrification to N2, nitrogen fixation turns N2 into NH3 (ammonia) - ammonia oxidation turns it into NO2-, nitrite oxidation will turn nitrite back to nitrate

115
Q

What is the oxidation and reduction reactions in the nitrogen cycle?

A

NO2- is oxidized to NO3-,
NO3- is reduced to NO2-

116
Q

What two forms of nitrogen can roots take up?

A

NH4+ through a direct NH4+ transporter
NO3- through symporter with H+, which is powered by H+ATPase

117
Q

Despite roots being able to take up nitrogen in 2 forms, what form is all nitrogen ultimately converted to?

A

NH4+

118
Q

What is primary nitrogen assimilation?

A

Incorporation of inorganic nutrients into organic substances like amino acids
- all NO3- is reduced to NH4+ before being assimilated
- everything is converted to NH4+

119
Q

What two enzymes are responsible for converting NO3- to NH4+?

A

Nitrate reductase converts NO3- to NO2-
Nitrite reductase converts NO2- to NH4+

120
Q

Where do nitrate reductase and nitrite reductase get the electron from to reduce the product?

A

From electron transporters / donors like NADPH

121
Q

What are the two main enzymes that assimilate inorganic nitrogen into organic molecules?

A

Glutamine synthetase (GS) converts glutamate to glutamine with an intermediate step, or NH4+ into glutamine

GOGAT - combines glutamine and 2-oxoglutarate (part of TCA cycle) and reduces to 2 glutamate

122
Q

What is an environmentally friendly strategy for improving nitrogen efficiency and reducing N pollution?

A

Legumes can acquire N from the atmosphere via special soil bacteria which are housed in nodules in roots
- co cropping or rotating with legumes can greatly enrich soil N content

123
Q

What form is phosphorus available as?

A

HPO42-
H2PO4-

124
Q

Below pH 7.2, which form of phosphorus is more prevalent and therefore mainly used?

A

H2PO4-

125
Q

What does a phosphorus deficient plant look like?

A
  • Stunted growth
  • dark green color
  • older tissue affected first as P is mobile in plants
  • reddish purple color may occur due to accumulation of anthocyanin pigments
126
Q

What acts as a facilitator for Pi uptake in most plants?

A

Arbuscular mycorrhizal AM fungi - which directly enter and interact with plant roots
- works in about 80% of plants

127
Q

List 4 adaptations of roots to enhance nutrient capture

A
  • Biochemical responses such as root exudates
  • fungal symbiotic partners like mycorrhizal
  • developmental responses like clustering roots around nutrient stores
  • prokaryotic symbiotic partners like nitrogen fixing bacteria
128
Q

Provide examples of how plant root and microbial exudate can increase Pi availability

A
  • microbial exudate - some microorganisms can exude phytase to convert phytate to Pi
  • Root exudate - roots can exude phosphatase to turn organic P to Pi
  • root exudate can also exude malate to convert Al-P to Al-malate and Pi
129
Q

What are cluster roots and how are they formed?

A

cluster roots are a cluster of roots that increase surface area and root exudation
- first inhibits primary root growth
- increases number and length of root hairs
- forms lateral roots
- enhances lateral root growth

130
Q

What is the phosphate transporters for uptake and transport

A

PHT1
- phosphate symporter

131
Q

What is the phosphate exporter that moves Pi into the xylem from the root?

A

PHO1
- moves Pi into shoot

132
Q

What does a potassium deficient plant look like?

A

substantial growth reduction
- yellowing on oldest leaves first - K is mobile in plants
- brown necrotic leisions develop within the yellow parts and eventually spread to cover the entire leaf blade

133
Q

What form of potassium is potassium often found and sold in?

A

Potash is potassium

134
Q

Are plants usually primarily limited by K?

A

no, K deficiency is uncommon but growth is usually stimulated by additional K supply

135
Q

5 reasons that make K an essential molecule

A
  1. K+ functions as a counterion for negatively charged molecules, including DNA and proteins
  2. K+ provides the stability for the dynamic structure of DNA and proteins
  3. Cofactor in some enzymatic reactions
  4. Main cation in central vacuole
  5. Generates potential gradient to create turgor pressure and provide structure to plant cells
136
Q

Which type of potassium transporter is used in different conditions?

A

HAK high affinity transporter is used un low concentrations of KCl

AKT - low affinity K transporter is used in very high concentrations of K

137
Q

Which K transporter is active and which is passive?

A

Low affinity transporter does not need ATP, high affinitiy (HAK) does need ATP

138
Q

K uptake from low K concentrations requires _____ energy than when K concentration is higher

A

more

139
Q

At a concentration of around 0.1mM of K, which type of transporter will be active?

A

Both AKT and HAK will be partially active
HAK will need 1x ATP instead of 2x ATP that is used at very low concentrations

140
Q

What is the role of the vacuole in K regulation

A

K is preferentially used in the cytoplasm, but will store up excess K in vacuole when cytoplasm is saturated - will take from vacuole first to keep cytosol at acceptable levels

141
Q

Define homeostasis

A

ability of an organism to maintain an internal stability in response to environmental changes
- important to the survival of plants
- allowing concsistency needed for plant function

142
Q

How do plants hanfle sodium in their bodies?

A

High affininty K transporters contribute to Na transport - preventing Na from reacing the photosynthetic cells in the shoot
- have a hard time distinguishing Na from K
- NHX - a sodium antiporter will move Na out of the cytoplasm

143
Q

Why is calcium an essential element in plants?

A
  • important role in forming a constituent of the middle lamella of the cell wall which binds neighboring daughter cells together
  • required at external surface of plasma membrane and tonoplast for membrane integrity
  • acts as a second messenger in signal transduction
144
Q

cells will preferentially take up potassium over sodium as long as ____

A

concentrations of K in the soil are higher than concentrations of Na

145
Q

What does calcium do for membrane integrity

A

helps connect adjaent phosphate groups of phospholipids

146
Q

How do roots take up calcium?

A

have both an open diffusion channel and an active ATPase and antiporter

147
Q

Why is magnesium an essential element

A
  • enzyme activities
  • energy transduction
  • chlorophyll structure (an essential component of chlorphyll A)
148
Q

Why is magnesium so important for energy transduction?

A

Mg 2+ forms a complex with ATP and ADP - only these complexes interact with ATPases during energy transduction

149
Q

define latent heat of evaporization

A

heat required to change one mole of liquid to gas at boiling point under standard atmospheric pressure

150
Q

A cell is plasmolyzed when ____, inside the cell is ____, outside the cell is ____

A

solute potential is lower outside (more solute) than inside (less solute) - water moves out of the cell, the cell inside is hypotonic, the cell outside is hypertonic

151
Q

Does water flow directly through the pit pair in trachieds?

A

no it is not an open passage - still blocked by primary wall and middle lamella - however water can permeate this
- the lignified (waterproof) secondary cell wall is not present at this location to allow for water transport

152
Q

What is a hydathode and what is guttation?

A

Roots will take up water due to osmosis (more solute in roots) which will build up positive turgor pressure and will push water up the plant - guttation is the name for water getting pushed up out of the plant - hydathodes are the pores that actually secrete the water

153
Q

Where is the site of greatest water resistance in the entire plant body?

A

Roots - because of suberin and Casparian strip - slows down water transport significantly

154
Q

why does energy input have to equal energy output?

A

to maintain leaf thermal stability

155
Q

Where can you expect the highest water potential in roots?

A

Root epidermis - water moves from hight to low potential - water flows into the plant

156
Q
A

BIOL 331 (2 decks)

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