chapter 4 plant physiology Flashcards
1
Q
Transport of CO2 and O2 in the leaves
A
- CO2 enters through the leaves for photosynthesis
- O2 leaves through the leaves as a product of photosynthesis
2
Q
Transport of CO2 and O2 in the roots
A
- CO2 leaves the roots as a product of metabolism/ cellular respiration
- O2 enter the roots to be used in cellular respiration
3
Q
Transpiration
A
- the movement of water and mineral nutrients from soil to the atmosphere via plants
- water will evaporate from leaf cells at <100% RH
4
Q
How much water is moved through transpiration per day?
A
- 0.5 gallons/day in one corn plant
- 52 gallons/day in one large maple
- transpiration is not seen
5
Q
Evapotranspiration
A
- landscape level movement of water from soil to atmosphere
6
Q
Where does water enter the plant?
A
- water enters through the fine roots
- these are found in the first couple inches in the soil
- the soil surface is significant
- deeper roots are for support
- water travels from the fine roots to the xylem
7
Q
What controls transpiration?
A
- controlled by guard cells of the stomata
- turgid guard cells open the stoma
8
Q
Why are stoma generally open in the day and closed at night?
A
- photosynthesis occurs with sunlight
- being open allows CO2 to get in but also allows loss of water
- closed at night to prevent excess water loss through stoma and transpiration
9
Q
What are xerophytes?
A
- dry plants that often have CAM photosynthesis
- close stomates during the day
10
Q
How does water move in and out of guard cells?
A
- overall controlled by K+
- more K+ in a cell = water will move into cell because of gradient
- when guard cells are turgid they open the stoma
11
Q
Why does increase in turgor pressure open the stomate?
A
- cellulose microfibrils of guard cells expand in length when hydrated
- because they are surrounded by other cells they elongate as much as they can and create the stromal opening
12
Q
What are leaf adaptations to growing in arid environments?
A
- epicuticle and several layers of epidermis
- sunken stomates with hair coverings
- sunken stomates and hairs help keep dry wind from causing excess water loss while still allowing CO2 in
13
Q
Types of water movement in plants
A
- apoplastic: water enters through cellulose that surrounds cortical cells, allows water to move more readily
- symplastic: water enters through cortical cells and moves from cell to cell, water is moved less readily
14
Q
Transpiration-cohesion theory
A
- water has cohesive and adhesive properties
- cohesive: water can stick to other water molecules via H bonding
- adhesive: water can stick to the cell wall in dead xylem cells. water interacts with polar substances. cellulose also has partial charges that can interact with water.
15
Q
How does water have cohesive and adhesive properties?
A
- the H2O molecule has both a partially positive and partially negative charge
- this allows H bonding between water molecules
- cellulose also has partial charges so it can form H bonds with water
16
Q
What is water potential
A
- water’s free energy or its ability to do work
- composed of solute potential and pressure potential
- solute potential + pressure potential = water potential
17
Q
Solute potential
A
- the effect of dissolved solutes on water potential
- always less than or equal to zero
- water moves toward more solute
- increase in solute [ ] decreases the solute potential (makes it more negative)
- add more solute = solute potential is more negative
- if no solute present, solute potential is 0
- cannot be positive
18
Q
Pressure potential
A
- effect of hydrostatic pressure of water potential
- most cells have a + pressure potential also called turgor pressure
- functional xylem cells have - pressure potential also called tension
19
Q
What is significant about the pressure potential of functioning xylem cells?
A
- they have a negative pressure potential or tension
- water is under tension and because of H bonding properties water can be pulled up the xylem
20
Q
Which way does water move?
A
- water always moves to the more negative water potential
- or toward the lower free energy
21
Q
Movement of water in a plant
A
- soil, root epidermal cell, parenchyma cell, functional xylem cell, leaf mesophyll (parenchyma) cell, atmosphere
22
Q
How does water move up the plant?
A
- the total water potential is more negative as you move up the plant
- water flows to the more negative water potential
- ex. root epidermal cells have a -0.1 MPa water potential and the soil has a 0 MPA water potential, so water moves from the soil to root epidermal cells
23
Q
What energy is used to transport this water?
A
- the flow of water to a lower free energy
- no ATP used
24
Q
What are the effects of soil salinity on soil and plant water potential?
A
- solute potential of soil becomes more negative and so its water potential becomes more negative
- if it gets too negative, the water won’t be able to get into the plant
25
Q
Why do parenchymal cells have a more negative solute potential?
A
- leaf parenchyma produces sugars from photosynthesis and store them, so they have more solute
- stem parenchyma also stores carbs which makes the solute potential more negative
- leaf parenchyma has more sugars, so it is more negative
26
Q
What are the major essential nutrients for plants?
A
- nitrogen
- phosphorous
- potassium
- magnesium
- sulfur
- calcium
27
Q
Importance of nitrogen for plants
A
- needed to make proteins, aa, and chlorophyll
- 4 N molecules needed per chlorophyll molecule to chelate the magnesium
28
Q
Importance of phosphorous for plants
A
- needed to make ATP, nucleic acids, and phospholipids
- phospholipids are important for membranes
29
Q
Importance of potassium for plants
A
- needed for guard cell regulation
- more in guard cell = stomates open
30
Q
Importance of magnesium for plants
A
- component of chlorophyll
- used by various enzymes
31
Q
Importance of sulfur in plants
A
- needed to make proteins and aa
32
Q
Importance of calcium in plants
A
- component of the cell wall
33
Q
Other minerals used by plants
A
- boron, chlorine, manganese, iron, nickel, copper, zinc, Mo: absorbed from soil and can act as cofactors for some enzymes
- hydrogen, carbon, and oxygen
34
Q
How do plants get H, C, and O?
A
- carbon is from CO2 and photosynthesis in leaves
- oxygen and hydrogen from water through the roots
35
Q
What are benefits of hydroponic production?
A
- less weight
- higher value of crop over winter
- better pest control
- better cost efficiency in the long run
36
Q
How were essential plant nutrients discovered?
A
- plants were grown in lab
- some lacked certain nutrients in water
- if a nutrient was missing and caused abnormal growth it was considered an essential mineral
37
Q
What is phytoremediation?
A
- the use of plants to clean up contamination from soils, sediments, and water
- works because plants absorb nutrients from the soil even if they are not necessary for them
- takes advantage of the unique and selective uptake capabilities of plant root systems
- environmentally friendly and potentially cost effective
38
Q
Translocation of sugars
A
- occurs in LIVING phloem sieve tube members
- requires ATP (chemical energy)
- moves sucrose form source to sink
- described by the pressure flow hypothesis
39
Q
What are the source and sink in the translocation of sugars?
A
- source: any part of the plant that is photosynthetic and produces sugars like the leaves or some stems
- sink: non-photosynthetic areas like the roots, storage areas, and some stems
40
Q
Explain the pressure flow hypothesis
A
- in the source: sucrose is actively transported (uses ATP) into cells to increase the [] inside the cell, because of this water also moves into the cell
- movement of water into the source cells increases and creates pressure to move the sucrose and water
- water moves through sieve tube members until it reaches the sink cell
- depending on the [ ] of sucrose in the area of the sink cell, sucrose moves out of the cell via active transport or down its gradient - both require and transport protein
- even though water is moved in this process this is NOT the main transport of water in plants
41
Q
How does water and mineral nutrient transport differ from sugar transport in vascular plants?
A
- water and minerals are transported via xylem
- xylem cells are dead at function
- sugars are transported via phloem
- phloem is alive at function
- movement of water does NOT require an energy source
- movement of sugars does require and energy source (ATP)
42
Q
Sugar and Slavery
What two plants provide virtually all the commercial sucrose worldwide?
A
- sugar cane and sugar beet
- led to the triangular trade from the 1500s-1800s
- britain, west africa, and the west indies
43
Q
What was traded in the triangular trade?
A
- britain received rum and sugar from the west indies & shipped firearms, cloth and salt to west africa
- west africa recieved from britain & sent salves to the west indies
- the west indies received from west africa & shipped rum and sugar to britain
44
Q
Metabolism
A
- cellular respiration processes
- glucose broken down to create energy
- oxygen is the final electron acceptor and becomes water
45
Q
Photosynthesis
A
- plants use light energy from the visible spectrum for photosynthesis
46
Q
What is the visible spectrum
A
- wavelengths from 400-700
- 40% of the radiant energy from the sun
47
Q
Photosynthetic pigments and green plants
A
- primary pigments: donate electrons in photosynthesis
- accessory pigments: part of light harvesting system
48
Q
What are the primary pigments in photosynthesis?
A
- chlorophyll 680 (PS2)
- chlorophyll 700 (PS1)
49
Q
What are the accessory pigments in photosynthesis?
A
- the rest of the chlorophyll a’s
- chl b
- carotenoids: carotenes (orange) and xanthophylls (yellow)
- form pigment/protein complexes in the thylakoid membrane
- transfer light to primary chl a so it can donate the electrons
50
Q
Chlorophyll structure
A
- amphipathic
- hydrophilic ring with Mg2+ and 4 N molecules that chelate the Mg2+
- hydrophobic hydrocarbon tail that allows chl to imbed into the membrane
- chl a: R group is CH3
- chl b: R group is a CHO
51
Q
Carotenoid structure
A
- mainly hydrophobic hydrocarbons that imbed into the membrane
52
Q
Are carotenoids or chlorophylls broken down in the fall?
A
- chlorophylls are broken down in the fall
- longer nights during the fall trigger chl breakdown
53
Q
Why is chl broken down rather than carotenoids?
A
- chl is made of Mg2+ and 4 N molecules
- N is the most limited essential nutrient for plants
- so chl is broken down so the plant can keep and store the Mg2+ and N until spring
- carotenoids made mostly of carbons and lost with leaves falling but C is easier for plants to get and make more when needed
54
Q
How is N the most limited mineral for plants to get if it is prominent in the atm?
A
- the N in the atm cannot be absorbed and fixed by plants
- it is absorbed by bacteria and fixed and released into the soil
- BUT when N is fixed it is mainly made into nitrate and nitrite
- nitrate and nitrite are negatively charged so they do no bind well to soil elements and leak OUT of the soil
- continual leaking from the soil prevents or makes it harder for plants to absorb N
55
Q
Absorption spectrum details
A
- chls absorb blues, purples, and reds but reflect greens
- carotenoids absorb green and reds but reflect yellows
- blues and reds spectrum primarily drive photosynthesis
56
Q
Photosynthesis phases
A
- light reactions: photochemical phase
- occur on the thylakoid membrane
- convert light to ATP and NADPH - Calvin cycle: biochemical phase
- occurs in the stroma
- converts CO2 into sugars and eventually sucrose with the use of ATP and NADPH
57
Q
Order of electron movement in photosynthesis light dependent reactions
A
- PSII (photosystem 2) w chl a 680
- plastoquinone
- cyt b6f complex
- plastocyanin
- PSI w chl a 700
- ferredoxin
- ferredoxin-NADPH reductase
58
Q
Significance of light reactions?
A
- occur in the thylakoid membrane
- movement of electrons creates a H gradient in the lumen of chloroplasts
- ferredoxin-NADPH reductase reduces an NADP molecule to NADPH
- ATP synthase uses the H gradient made to synthesize ATP
- ATP and NADPH are made into the stroma and needed for the Calvin cycle that also occurs in the stroma
59
Q
Why is NADPH significant?
A
- it is made from the light reactions
- it is the electron source that is needed in the calvin cycle
60
Q
Ph difference of the lumen and stroma
A
- lumen: 5
- stroma: 8
- lumen has 1000x more H+ making it much more acidic
61
Q
Calvins Experiment
A
- experiment was used to determine the intermediates and processes of the calvin cycle
62
Q
Rubisco enzyme
A
- Ribulose bisphosphate carboxylase/oxygenase
- enzyme responsible for the carbon fixation in the C3 cycle
- can aid in photorespiration or carboxylation
63
Q
Photorespiration
A
- rubsico catalyzes the combining of O2 to RuBP
- oxygenase activity
- this is not a benefit b/c no C is being brought into the plant
- O2 %: 20-21% (used to be 0-1%)
- percentage was brought up by plants photosynthesizing
64
Q
CO2 fixation (carboxylation)
A
- Rubisco combines RuBP and CO2 to ultimately form sugars
65
Q
Photorespiration and CO2 fixation
A
- competing reactions at the same active site of Rubisco
- because both CO2 and O2 can bind
66
Q
Rubisco concentration
A
- 4mM in the stroma (500x the [CO2])
- this is unique because normally there is a higher [ ] of substrate rather than enzyme
- makes rubisco the most abundant protein on earth (25% of total leaf protein)
- because plants make up most of the biomass
67
Q
Rubisco affinity
A
- fixed CO2 80x faster than O2
- higher affinity for CO2
- good for plants so they can make sugars
- at 25 degrees CO2 fixation outruns oxygenation only by 3:1
- at higher temps, photorespiration increases
68
Q
O2 and CO2 concentrations
A
- O2: ~20% in atm
- CO2: ~0.04% in atm
- bad news for plants because more oxygen is available rather than CO2
69
Q
C4 cycle properties
A
- found in tropical grasses (maize, sugar), warm-season prairie grasses (big and little bluestem). crabgrass, pigweed, etc.
- seen mainly in monocots but some dicots
- leaves have thick-walled bundle-sheath cells
- has more energy requirements
- works well at high temps but not in lower temps
70
Q
C4 cycle purpose and costs
A
- increases CO2 concentration in bundle sheath cells
- plants can reduce photorespiration and water loss in hot, dry environments
- increases CO2 concentration allows stomates to be closed more to prevent water loss
- it costs ATP (less efficient if env is not hot and dry)
71
Q
C4 mechanisms process:
A
- PEP is carboxylate into OAA via PEP carboxylase in the chloroplasts of leaf mesophyll cells (fixes CO2 more readily via PEPC)
- OAA is transferred to bundle sheath cell chloroplast in the form of malate
- malate is decarboxylated into pyruvate (CO2 that comes off is taken into the Calvin cycle)
- pyruvate is converted to PEP in the leaf mesophyll in a series of steps (requires ATP)
- enhances CO2 [ ] to limit photorespiration
72
Q
CAM cycle properties
A
- aka crassulacean acid metabolism
- an adaptation to arid environments
- CAM plants open stomates at night and keep them closed during the day
- also uses PEPC as initial carboxylation enzyme
- same intermediates as C4 but used in different ways
73
Q
CAM plant examples
A
- cacti
- pineapple
- agave
- some orchids
74
Q
CAM at night
A
- stomates are open at night to allows CO2 in
- CO2 is used to convert PEP to OAA via PEPC in the chloroplast of leaf mesophyll cell
- OAA is transferred as malate to the vacuole of leaf mesophyll cell
- malate remains in vacuole until day time
75
Q
CAM in the day
A
- malate is transferred to the chloroplast
- malate is decarboxylated into CO2 and pyruvate
- CO2 is used in Calvin cycle
- pyruvate can be converted to PEP via ATP to be used again at night
76
Q
Cellular respiration
A
- break down glucose to create energy
- glycolysis, pyruvate DH, CAC, ETC
- O2 is the terminal electron acceptor
