Midterm (Plants) Flashcards
(120 cards)
1
Q
Opisthokonta
A
group of animals and fungi
2
Q
Regulators
A
- have a zone of stability, keeping its internal env around a set point
3
Q
Feedback mechanism
A
System -> Sensor -> Integrator (brain) -> Amplifier (+/-)
4
Q
Growth
A
irreversible increase in size
5
Q
Development
A
qualitative change occurring at particular life stage
6
Q
Morphogenesis
A
development into a particular shape
7
Q
Diffusion Equation
A
= 2Dt (diffusion coefficient)
8
Q
Convection
A
bulk flow through vessels using a pressure gradient
9
Q
Primary Active Transport Example
A
K+/Na+ pump
10
Q
Secondary Active Transport Example
A
sucrose transport
11
Q
Gap Junction
A
channels connecting adjacent cells (in animals)
12
Q
Plasmodesmata
A
channels connecting adjacent cells (in plants)
13
Q
Visible light spectrum
A
400nm-700nm
14
Q
Quantum Yield
A
product / # quanta absorbed
15
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Action Spectrum
A
O2 evolution for a given wavelength
16
Q
Max Quantum Yield
A
1 O2 per 2500 chlorophyll => 8 quanta per 300 chlorophyll
17
Q
Red Drop
A
QY drops at 700nm despite higher absorption
- far-red light alone not efficient for photosynthesis
- both far-red and red light (<680nm) required for the synthesis
18
Q
Chloroplast Structure
A
Lumen (inside thylakoid)
Granule (group of thylakoids)
Thylakoid (one of the UF-like things)
Stroma (outside thylakoids, inside chloroplast)
19
Q
Chloroplast ETC Flow
A
P680 (photolysis) -> Pheophytin -> Plastoquinone -> Cytochrome-C (H pump) -> Plastocyanin -> P700 -> Ferodoxin -> NADPH reductase
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Cyclic Electron Flow
A
Ferodoxin donates electron to Cytochrome-C
21
Q
Chloroplast ATP Synthesis
A
Lumen accumulates high H+, drivers ATP synthase
22
Q
Lollypop experiment outcome
A
PGA 3C first to be produced
RuBP 5C is second to be produced
23
Q
Dark Reaction Flow
A
3CO3 + 3RuBP —–(carboxylation, RuBisCO)—-> 6PGA
6PGA + 6ATP —(phosphorylation)—-> 6 diPGA
6 diPGA + 6NADPH —–(reduction)—–> 6 G3P
5 G3P + 3 ATP ——(regeneration)——> 3 RuBP
24
Q
Dark/Light effect on Calvin Cycle
A
Dark = PGA accumulates, RuBP depletes Light = PGA depletes, RuBP accumulates
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RuBisCO
```
most abundant protein on planet
very slow
8 small subunits nuclear genome
8 large subunits chloroplast genome
reacts with Co2 or O2 (Co2 affinity much higher, but [O2] much larger)
```
26
Photorespiration
RuBP + O2 = 3-PGA + 2-PGA
conversion of 2-PGA to 3-PGA takes ATP and O2
peroxisome uses O2
mitochondria releases CO2
angiosperms have highest carboxylation/oxygenation ratio
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C4 Photosynthesis Process
PEP (pyruvate derivative) + CO2 = malate or aspartate
happens in mesyphyll, using PEP carboxylase
Releases CO2 into bundle sheath cell
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C4 Photosynthesis Results
twice CO2 assimulation for same water
very little photorespiration
[CO2] = 50uM in bundle sheath cell
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CAM Photosynthesis Process
At Night:
Starch (from chloroplast) -> PEP
PEP + CO2 -> Malic Acid (in vacuole)
During Day:
Malic Acid -> CO2 + pyruvate -> starch (in chloroplast)
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CAM Photosynthesis Results
Almost no photorespiration
| [CO2] = 200uM during day
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CPP
```
Carbon Compensation Point
concentration at which plant has zero net carbon gain
C3: very high ppm
C4: very low ppm
CAM: almost 0 ppm
```
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LCP
Light Compensation Point
| light intensity at which plant has zero net carbon gain
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Light Response Curve
logarithmic curve with y-intercept being LCP
left of light saturation point is zone of light limitation
right of LSP is zone of carboxylation limitation
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Phenotypic Plasticity
Variation of phenotype based on environment
| Ex: plants grown in shade have different light response curve
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Leaf Saturation Point
- leaves saturate at a point lower than maximum sunlight radiation
- leaves usually shading eachother
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Shade Adaptation/Acclimatization
- under forest canopy, green & far red wavelengths most abundant
- plants increase PS2 to PS1 ratio (PS1 not as light limited)
Others:
- increase chlorophyll production
- convex epidermal cells (adaptation)
- leaf size and shape
- leaf angle
- solar tracking (adaptation)
37
Excess Light Effect
- can sunbleach plants (photo-oxidative damage, excites O2)
- can be dissipated by cholorophyll movement to sides
- can increase zeaxanthin ratio (more heat dissipation)
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Xanthophyll Cycle
Increase zeaxanthin to violaxanthin ratio
- when high light/low water (ex: winter, daylight)
- more heat dissipation, less damage
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Dynamic Photo-inhibition
Photo-oxidative damage causing shallower light response curve, but same max photosynthesis
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Chronic Photo-inhibition
Caused by prolonged or high light exposure
| Caused lower max photosynthesis
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Plant Response to Heat
Photosynthesis increases, but
| Photorespiration increases faster (C3 plants suffer the most)
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Heat Coping Strategies
leaf rolling
opening stomata (high decrease temp
higher edge area
reflective coating or hairs
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Heat Loss Mechanisms
Radiative Heat Loss (photons not absorbed)
Sensible Heat Loss (air movement, circulation)
Latent Heat Loss (evaporation)
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Carbon Concentration Response
C3 have most to gain from increased carbon
| C4 mostly limited by light
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O2 Concentration Response
C3 gain most from lower O2 concentration
| Lower O2 means less energy for reproduction
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Leaf Angle
Plants adjust angle of leaves to distribute light
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Leaf Area Index
leaf surface area / ground surface area
- determinant of yield
- proportional to dry matter produced
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Crop Yield
y = plant density * weight per plant
When plants don't interfere with each-other, yield is density dependent
When plants compete for resources, yield is density independent
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Glycolysis Overall Reaction
sugar + 2 ATP -> organic acid + 4 ATP + 2 NADH
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Glycolysis Output (Animals/Plants)
Animals: glucose -> pyruvate
Plants: sucrose -> pyruvate or malate
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ETC in Plants - Differences
- two additional dehydrogenases
- NAD(P)H dehydrogenase, facing IMS
- NADH dehydrogenase, facing matrix
- alternate oxidase, producing heat instead of ATP
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Thermogenic Flowers
- > 45C
- usually large plants (for heat retention)
- could be used for spreading scents
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Animals Anaerobic Respiration
pyruvate ---(NADH)--->
lactic acid ---(ATP)---->
glycogen (muscles) or glucose (liver)
Much more ATP needed to convert lactic acid than output of glycolysis
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Plants Anaerobic Respiration
- starts with lactate fermentation
- as pH drops, lactate dehydrogenase activity gets slower & pyruvate decarboxylase speeds up
- ethanol fermentation becomes main pathway
pyruvate ----(pyruvate decarboxylase)--> +CO2
acetylaldehyde ----(alcohol dehydrogenase, NADH)-->
ethanol
Ethanol diffuses more easily out of plants
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Respiratory Quotient
Volume CO2 produced / Volume O2 consumed
Carbohydrates: usually 1.0
Fats: closer to 0.7
Proteins: closer to 0.8
Helps measure percentage of metabolized macromolecules in organisms.
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Water Potential Equation
total water potential = pressure + solute + gravitational + matric
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Water Pressure Potential
- due to hydrostatic or turgor pressure
- only for closed systems
- usually positive (negative means suction)
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Osmotic/Solute Potential
- due to solute in water
- only matters if there's a membrane involved
- usually negative
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Water Gravitational Potential
- relative to a reference height
| - negligeable at small scale
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Matric Potential
- involves colloidal solutes (high SA)
- usually negative
- usually negligible in cell/tissue
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Water moving through soil
- moves by bulk flow
- from wet to dry
- plants leave dry patch around roots
- young roots more permeable
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Apoplast Pathway
- moving through cell walls/outside membranes
| - blocked by Casparian strips
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Casparian Strips
- wax strips forcing water to travel through endoderm cells
| - present between root cortex and xylem
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Symplast Pathway
- through plasmodesmata/inside membrane
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Transmembrane pathway
crossing through cell walls/membranes
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Water travelling through roots
hairs -> cortex -> endodermis (apoplast blocked by casparian strips) -> xylem
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Mycorrihizas
- mutualist organism present in 92% plant families
- increase SA or roots => increase water and mineral uptake
- some are decomposers and increase mineral uptake
- critical for orchid germination
- plant provides sugar back to fungi
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Endomycorrihiza
Permeates the cell membrane of roots
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Ectomycorrihiza
does not permeat cell membrane of roots
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Hemiparasites
- detect strigalactone => germinate
- steal from xylem and phloem
- use haustoria (root-like things), and opening stomata to increase transpiration
- ex: Striga
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Mycorrihizea Association
```
plants release strigolactones into soil
=> inhibit plant shoots and stimulate fungal chemotaxis
=> fungi signals back
=> plant creates pre-penetration apparatus (PPA)
=> hyphea penetrates PPA
=> hyphea grows along root length
=> PPA penetrates cortex
=> nutrient exchange takes place
```
72
Most Limiting Nutrients (Plants)
N, S, K
| nitrogen more than others, most applied fertilizer
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Mineral Availability from Soil
pH has large effect on nutrient availability, since minerals are ionized
- soil particles are negatively charged, so cations bind easily to them
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Plant Nutritional Deficiencies - Diagnosis
- Deficiencies in mobile nutrients tend to show in older - leaves first
- Deficiencies in immobile nutrients (iron, calcium, Mn, S) show in young leaves first
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Nitrogen Deficiency Diagnosis
```
Rapidly inhibits growth
Acute:
- chlorosis of leaves (yellowing)
- leaves shrivel and die
Chronic:
- slender woody stems
- buildup of carbohydrates, less proteins
- buildup of anthocyanins - leaves turn purple
- maybe due to sensitivity to light
```
76
Oxidized Nutrient Assimilation
Absorbing N, S and P is hard because they're usually in highly oxidized form
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Nitrate assimilation
NO3 -> NO2 (toxic) -> NH4 (toxic) -> glutamine
12 ATP per N
Plants store excess ammonium in vacuoles
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Nitrogen Fixation Methods
Lightning (8%) - produce ROSs that produce NO3
Photochemicals (2%) - NO and O3 -> HNO3
Bacteria and Cyanobacteria (90%):
- N2 -> NH3
- need anaerobic environment, since O2 can damage
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Filamentous cyanobacteria
- multicellular
- have heterocysts:
- sense gradient of nitrogen, which triggers differentiation
- can't multiply
- lacks PSII (to stay anaerobic)
- needs sugars from neigbors
80
Root Nodules
From plants that in symbiosis with N-fixing bacteria
- O2 concentration 10 000x lower than environment
- oxygen binding legehemoglobin (high affinity)
- protects nitrogenase
- gives pink color
- transports O to bacteria terminal oxygenase (much lower Km)
81
Root Nodule Formation
```
Plant release flavinoids
=> bacteria release Nod factors
=> root hairs curl
=> bacteria infect root by dissolving cell wall
=> root nodule forms
```
82
Plant penalizing cheating non-fixers
Starve them of O2
| - shown experimentally by replacing N2 by Argon and forcing bacteria to be cheaters
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Percent evaporation per plant part
90% stomatal transpiration
| 10% cuticle transpiration
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Xylem constitution
Xylem Elements (Angiosperms)
- perforated dead cells
Tracheids
- long perforated dead cells
85
Cohesion-Tension Theorem
- water pulled through water column through tensile strength
| - narrow xylem contribute to adhesion to cell wall, increasing effect
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Embolism
air vapor bubble in xylem breaking water column
- caused by stress, drought, insects
- can by bypassed by lateral xylem movement
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Root Pressure
Hydrostatic pressure resulting from osmotic potential difference between soil water and xylem sap (ionic solution)
- can repair embolisms
- can only account for short distance travel (1 meter)
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Stomata Gas Exchange
H2O diffusion much greater than CO2
| Affected by relative humidity
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Transpiration Equation
(Water Potential Leaf - Water Potential Atmosphere) / Resistance due to Waxy Cuticle
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Boundary Layer
Layer of still air around leaves (ex: trichomes)
Higher wind -> thinner layer -> more transpiration
Shorter leaf -> small thickness of layer -> more transpiration
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Stomata conductance
Related to stomata aperture
| Guard cells turgor affect resistance (increase solute -> stomata close)
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Water Loss Tradeoff
Gaining more CO2 has diminishing returns
- riverside plants keep stomata open
- higher CO2 concentration overall means ability to close stomata more
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Water Potential Diurnal Fluctuation
Biggest water potential difference at end of day
| Lowest water potential difference at dawn
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Translocation
Process in which assimilates (sugars) are transported through-out plant
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Girdling
Cuts off phloem by cutting outer edge of stem/trunk
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Sieve Tube elements
- zombie cells organized end to end, seperated by sieve plates (porous)
- each sieve element has companion cell
- element only contains smooth ER, some mitochondria, some plastids
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Example Sinks and Sources
```
Source:
- young/mature leaves
- cotyledon (while seedling)
Sink:
- expanding leaves
- older leaves
- roots
- fruits (very competitive)
```
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Orthostichy
- leaves in same column will act as source/sink to eachother
| - if leaves in one orthistichy are removed, plant will reroute
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Phloem Sap
Mostly sugar by weight, some proteins and ions
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Phloem Loading
Mesophyll sugars getting loaded into phloem
| Either symplastic or apoplastic loading
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Symplastic Loading
flowing sugars through plasmodesmata
| - simple diffusion
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Apoplastic Loading
sugars flowing into apoplast
sugars actively transported into sieve elements
- proton pump and proton/sucrose symport
- can pump against gradient
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Pressure-Flow Hypothesis
Osmosis is the driving force for assimilates
- Assimilates are transported from sources to sinks by the bulk flow of water along a gradient of osmotically generated turgor pressure
Assumptions:
- sieve plate pores unobstructed
- simultaneous bidirectional transport impossible
- low ATP requirements
- turgor higher in source sieve elements
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Plant Growth Types
Determinate Growth: flowers, leaves, fruit
Indeterminate Growth: shoots, roots
Primary Growth: shoots & roots
Secondary Growth: increase thickness (wood/bark)
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Relative Growth Rate Equation
(log L2 - log L1) / (t2 - t1)
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Cell Growth Rate
E(P - Y)
E = extensibility of cell walls
P = turgor pressure
Y = threshold turgor pressure for growth
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Types of Meristems
```
Apical Meristem
- shoot apical meristem
- root apical meristem
- inflorescence/floral meristem
Lateral Meristem
```
108
Apical Meristem
- tip of roots and shoots
| - produces new structures
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Lateral Meristem
- responsible for secondary growth
- occurs at cambium
- produces bark/wood
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Parts Apical Meristem
Protoderm -> Epidermis
Ground Meristem -> Cortex
Procambium -> Vascular Bundles (vascular cambium, xylem, phloem)
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Plant Cortex
- undifferentiated cells
| - store tanins, carbohydrates, resin, etc
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Root Meristem Zones & Parts
Zones:
Maturation (root hairs)
Elongation
Cell Division
Parts:
- root cap
- quiscence center (backup reserver)
- apical meristem
113
Shoot Parts
Leaf primordia
| Bud primordia
114
Secondary Growth
- Growth happens towards and away from center from the vascular cambium
- Epidermis differentiates into cork as it grows
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Bark Parts
Periderm (outer edge)
Cork
Secondary Phloem
116
Plant hormones types
Gibberellins
Auxins
Cytokinins
117
Gibberellins
- causes hydrolysis of starch in internodes
| => increase turgor pressure (P)
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Auxins
- stimulates proton pump towards cell wall
=> increase extensibility of cells (E)
- produced by shoots and travels down
- only stimulates exciced stem segments
[Auxins] > [Cytokinins] => root development
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Cytokinins
- produced by roots and travels up
| [Cytokinins] > [Auxins] => shoot development
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Totipotency
Adult plant cells are able to give rise to an entire differentiated plant
