Module 2 Flashcards
(110 cards)
1
Q
What are 5 main roles of water in plants?
A
- Evaporative cooling
- Turgor
- Cellular reactions
- Phloem transport of sugars and hormones
- Uptake of mineral nutrients
2
Q
What are two main components of water potential
A
- Solute potential
- Pressure potential
3
Q
How can plants manipulate water potential
A
Adding or removing solutes in cells by phloem loading
- Closed stomata (less water)
- More negative solute potential in cells with more solutes
4
Q
Negative water pressure potential vs positive water pressure potential
A
- Negative potential means low pressure
- Positive potential means high pressure
5
Q
What is turgor?
A
In non-woody plants, structure comes from turgor pressure
- Water that ensures a plant maintains its shape
6
Q
Explain what mechanism allows water to move from ground to leaf
A
- Moves from soil to root to xylem to leaf - it is always moving from HIGH to LOW pressure
- Moves down potential gradient (turgor pressure)
7
Q
What happens to solute potential when plants wilt?
A
Solute potential is negative because there is less water in cells.
Cells are flaccid, so pressure potential is 0
8
Q
What is solute potential in a normal plant?
A
Slightly negaitve, while turgor pressure is positive.
Cell contents are dilute
9
Q
What 4 things does transpiration facilitate/allow?
A
- Nutrient transport
- Evaporative cooling
- Water needed for growth and cellular reactions
- Turgor (plant structure)
10
Q
What are four characteristics of xylem?
A
- Dead, fit via perforations
- Allow rapid flow without resistance
- Up to 45 m/hr
- Hollowed out, allowing speed
11
Q
What is root pressure?
A
Hydrostatic pressure resulting from high ion concentration in the roots.
- Incentivizes water to enter roots to dilute it, triggering increased uptake of soil water
12
Q
What is the cohesion-tension theory?
A
From roots to the leaves, there is a continuous water column -
Cohesion between water molecules
Adhesion between water molecules and cell walls
13
Q
What is the cohesion-tension theory?
A
From roots to the leaves, there is a continuous water column -
Cohesion between water molecules
Adhesion between water molecules and cell walls
14
Q
What is cavitation?
A
Formation of an embolism - a bubble in the stem that prevents water movement
15
Q
Explain the concentration gradients of CO2 and H2O in a leaf
A
Go in opposite directions
- Concentrations gradient is stronger for H2O
- H2O smaller than Co2 so it diffuses faster
When CO2 comes in, H2O goes out
16
Q
Explain the “necessary evil” in plant photosynthesis
A
In order to photosynthesize, plants must constantly lose water - must open stomata for CO2 consumption
17
Q
What two things drive transpiration?
A
Force and Resistance
- Force is the difference in water potential between air and soil
- Greater resistance - less evaporation
18
Q
What are 3 versions of resistance in plants?
A
- Cuticle - wax on leaf surface, often thick in desert plants
- Stomata - variable conductance
- Boundary layer - layer of still air. When it’s thicker there is less evaporation.
19
Q
What is a fur trap? Explain it’s graph
A
“fur” on leaves that help to create a boundary layer
20
Q
How does leaf size impact boundary layer?
A
Shorter leaf size often means
- smaller thickness of boundary layer
- lower air resistance
- more transpiration
21
Q
What is formula for transpiration?
A
transpiration = (water potential of leaf - water potential of atm)/ resistance
22
Q
What two things might increase transpiration?
A
- Air was drier (higher water potential gradient)
- Resistance went down
23
Q
What is the function of stomata?
A
- Open and close via TURGOR pressusre
- Cells open when turgid, collapse when flaccid
24
Q
Explain the three points of stomatal conductance related to photosynthetic rate
A
- Tightly closed - CO2 might limit photosynthesis
- Ideal point where CO2 H20 exchange is optimal
- Wide open - rate of transpiration may be more than needed, losing water
25
4 options for plants when water is low
- Die
- Adapt
- Evade
- Tolerate
26
What are 4 reasons nutrients might be in low supply?
- Very old soils
- Decomposition is slow due to temperatures
- High clay content (tropics)
- Competition between plants, other plants, and microbes
27
What is the Haber-Bosch process?
nitrogen is extremely limiting in agriculture, farmers used to lay manure in order to get it
- haber-bosch process allows making of fertilizer from the air,
28
How do plants respond to deficiencies in
- calcium
- iron
- nitrogen
- CO2
- phosphate
- potassium
- manganese
- magnesium
- calcium: new leaves are misshapen or stunted
- iron: leaves are yellow and white with green veins
- nitrogen: light green upper leaves, lower leaves are yellow
- CO2: white deposits on leaves
- phosphate: leaves are darker than normal
- potassium: yellowing at tips and edges
- manganese: yellow spots or elongated holes between veins
- magnesium: lower leaves turn yellow from outside going in
29
Explain toxic elements in plants and soils
Soil is complete mix of nutrients and toxic elements in a variety of chemical forms
- plants must get the appropriate elements while excluding, detoxifying or tolerating the toxic ones
30
Explain root foraging
- larger more spread roots at lower nitrogen
- Higher root:shoot ratio
31
What is proliferation
Roots will increase their roots in nutrient rich patches
32
What is the role of plant rooting in niche creation?
Plants root differently - this is how different niches are created, enabling plant coexistence
33
Explain phosphorus uptake by plants
P can occur in soil as complex organic molecules that plants can't take up directly
- Roots an exude phosphatase enzyme into soil that cleaves organic P into smaller, simple molecules that can be taken up
34
What are two uptake systems in roots?
- Symplastic (through cells)
- Apoplastic (via cell walls)
35
What are three versions of nutrient acquisition for plants?
- Foliar uptake of nitrogen
- Parasitic plants
- Carnivoroues plants
36
How does a parasitic plant work?
Use special structures (Haustoria) to tap into the xylem and phloem of other plants
37
Explain the intensity of nutrient assimilation
- The assimilation of highly oxidized nutrients is among the most intense reactions in living organisms
- Many compounds are toxic if not assimilated or sequestered
38
Explain phloem recycling
N and P are valuable and expensive
- They are recycled and broken down into constituent nutrients that are reabsorbed into the stem and used to build new leaves again
39
What is adaptation of plant resorption in nutrient limiting ecosystems
Plants in nutrient limiting ecosystems have adapted to have better resorption
40
What are ways a plant can deal with toxicity?
- immobilization by mycorrhizal associations
- binding to plant cell wall
- chelation
- reduced influx into plasma membrane
41
What is mutual symbiosis?
Plant trades a resource it has in abundance with another organism for another resource
- trade organic carbon with nitrogen or phosphorus
42
What organisms are able to perform N2 fixation?
- Only prokaryotes and archaea can fix nitrogen using nitrogenase
43
What is specific condition under which nitrogenase works?
Nitrogenase only works in anaerobic conditions
44
Explain the rhizobia-legume symbiosis
- Mutualistic symbiosis - nitrogen is made available for legume, while legume provides bacteria with a "home"
- Uses nodules, where bacteria fix nitrogen within the legume
- Plant provides carbon, bacteria provides fixed nitrogen
45
How does the signal between rhizobia and legume work?
1 - Plant root produces a **flavonoid ** that attracts the rhizobia, which serves as a signal
2 - Most rhizobia produce a NOD factor, which identifies them as appropriate symbions
3 - Plant sense the nod factor, and prepares to form a symbiotic nodule structure
46
What is a nod factor
In rhizobia that works as a signal to show that it can establish a relationship with legume
47
How do nodules develop in legumes?
rhizobia live in bacteria - when they make contact wiht plant they create a "root hair", then create an infection thread.
- In wild type plants, bacteria enter the root hair
- In nod-factor receptor mutants, bacteria are unable to enter the root hair
48
What is leghemoglobin?
- Leghemoglobin delivers oxygen to respiring symbitoic cells (bacteria need high O2 for respiration)
49
What is autoregulation of nodulation?
Fixation is expensive - legumes downregulate fixation when they have enough nitrogen
50
Explain N-fixation and forest succession
- Nitrogen fixating trees grow quickly and fix a lot of nitrogen during early forest regrowth to meet demands
51
What are the two types of mycorrhizal associations?
- Ectomycorrhizal fungi: proliferate outside the root and between cells (mushrooms)
- Endomycorrhizal fungi: penetrate plant call walls ~80% of land plants
52
What initiates branching of fungal hyphae?
Strigolactones - produced by plant roots
53
What do fungi produce that identifies it as a symbiont?
a Myc Factor
54
Explain the 3 steps in symbiosis formation
- Plant root produces strigolactones, initiating branching of fungal hyphae
- Fungi produce a Myc factor, identifying it as a symbiont
- Plant prepares to permit fungi to penetrate its cells
55
Explain orchids and fungi
Orchids rely entirely on mycorrhizal fungi in their early life stages
56
What is the phantom orchid?
Orchid that doesn't photosynthesize, it parasitices ectomycorrhizal fungi to obtain its carbon
57
5 pros of symbioses
- enhances yield
- improves nutrition
- enhances abiotic stress tolerance
- increase soil stability
- protects from some pathogens
58
What is rhizodisposition?
All material lost from plant roots (mucigel, amino acids, sugars)
59
What is the lupin mutant?
Lupin mutant doesn't form root nodules - even under low nitrogen
- plant is sending out wrong signals
- Plant can't form an infection thread
60
What "symptoms" might the lupin mutant show?
- chlorosis
- slow growth
- lower synthetic rate
- greater root:shoot ratio
- upregulated root transporters
- greater N recyling
- more susceptible to pathogens
61
What are plant senses?
## Footnote
q
- Ability to detect environment
- Inform 'decision making'
-
62
What are cues for every sense?
- sight : electrochemical radiation
- hearing : vibrations/air pressure waves
- touch : direct physical stimulus
- smell : airborne chemicals
- taste : soluble chemicals
- magnetoreception : magnetic fields
63
What is phototropy vs. thigmonasty?
- Phototropy: plants moves toward light, stimulus determines directional response
- Thigmonasty: plant moves in response to touch, direction is independent of the stimulues
64
What 5 plant processes are cued by light?
- phototropism
- seed germination
- chloroplast movement
- flowering and scent emission
- stem elongation
65
What aspects of light are sensed by plants?
Sensed by photoreceptors
- intensity
- direction
- wavelengths
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66
What does blue vs red light mediate in plants?
- Blue and UV mediate phototropism and stomatal opening
- Red and far red activates seed germination
67
What does ratio of red to far red light mean for plants?
Indicates day length for plants
due to interconversion of photochrome proteins
68
What is mechanoreception?
Touch acting as a cue for plant processes
- highly active in climbing plants
- mimose rapid leaf folding
- thigmotropism is a positive touch response (twining plants and tendrils)
69
What is the turgorin compound?
Turgorin behaves like a neurotransmitter to establish potentials across membranes
70
Explain gravitropism
Shoots grow against gravity, roots grow with it
- Starch grains at the root tips (amyloplasts) fall in the direction of gravity
- Secondary receptors - polar auxin transport
71
How does the sound of running water impact plant growth?
Plant roots grow towards the vibrations generated by running water
72
Explain sensing of neighbours in plants
Lots of plants in one place could increase herbivory so plants may avoid this
73
Why are plants highly susceptible?
What are possible pathogens?
They have no avoidance mechanism
possible pathogens are
- fungi
- bacteria
- viruses
- protozoans
74
Give 3 examples of physical defences and chemical defences
physical:
-thorns
- barriers
- Ligning
chemical:
- latex, oils
- secondary metabolites
- detoxifying enzymes
75
What are parasitoid wasps?
Outsourced defense mechanism of plants
- when plant sense wounding, it signals a pathway that releases volatile attractants
- this attracts wasps that will lay their eggs within catterpillars (also protecting plant)
76
3 ways a plant detects attack
- detects vibrations
- recognition of saliva or oviposition secretions
- mechanical damage - wounding
77
Explain constitutive vs induced defence
Defences can be put up or are "always there"
78
What are 3 local defence responses of a plant?
- oxidative burst - 'firestorm'
- lignification - 'walling the pathogen in'
- hypersensitive - 'deliberate cell death' - doesn't defend against fungus
79
What are the types of defensive compounds?
- detoxifying enzymes (breakdown toxins)
- alkaloids (inhibit enzymes)
- terpenoids (lyse red blood cell)
- phenolics (endocrine disruption, inhibit digestion)
- neurotoxic amino acids
80
Explain Monarch Butterflies evolution in response to plant defence
- They have evlolved resistance to a cardiac glycoside in milkweed that can kill other insects
81
What is the difference between a primary and secondary metabolite?
Primary metabolites are produced in all plants and are directly involved in growth and development
Secondary metabolites are more specialized - not absolutely required
82
Secondary metabolites roles
- defence
- communication
- stress mitigations
83
What are the three main types of secondary metabolites?
1- terpenes
2 - phenolics
3 - N-containing compounds
84
What are terpenes?
- Largest class
- Built of 5 Carbon units
- Water insoluble
- in essential oils, carotenoids, rubber, etc.
- responsible for scent and flavour in cannabis
-
85
What are phenolics in plants
- Benzene rings made from sugars
- found in all plants
- include flavonoids, polyphenols, tannins (used in cancer research)
- involved in pigmentation, stress tolerance, defence and communication
- tea!
-
86
What are N-containing compounds in plants?
alkaloids
- found in 20% of vascular plants from amino acids
- High neuroactive effect on vertebrates when consumed
87
What are glycosides?
A sugar bonded to non-sugar group
Can be terpene or phenolic
88
What is Glycone vs Aglycone
- Glycone is sugar
- Aglycone is non-sugar
89
What are cardiac glycosides?
- Found in plants but compounds highly impact cardiac in species that consume them
- Interfere with the sodium pump in the heart
- Small doses are sometime administered as medicine
> 2 ng/mL is toxic
90
What are milkweeds in plants?
Leaves that conatins cardenoloids - a milky sap that is toxic to mammals but food source to monarch butterfly
- protects monarch against predation and lowers their competition
91
What is a cyanogenic glycoside?
- N-containing compound found in peach pits, apple seeds, etc.
- Break down to form cyanide, which blocks cell resp
92
Why might plants in cold climates be acyanogenic?
Less harbivory - less need for poison
Risk of 'suicide' in freezing - if seed breaks open then whole plant is poisoned
93
What is associated with the Cassava plant?
Containes cyanogenic glycosides - easy to grow but if not properly detoxyfied then can be poisonous
94
What are Glandular Trichomes?
Secondary metabolites that burst on contact
' stinging nettle'
release histamines, oxalic acids, tartaric acids, formic acid, serotonin...
95
What is allelopathy between plants?
Biochemicals are passed between nearby plants to influence their growth. Inhibit growth of other species
96
What are capsaicinoids?
In mammals they bind to receptors in mucous membranes, creating a burning sensation
- Insoluble to water
Fruit is made to be unpalatable to allow for targeted seed dispersal (birds lack responsive receptor to the spice)
97
What are phytohormones>
plant hormones that regulate plant physiology, growth, development, reproduction, and responses to environment
98
7 roles of hormones in plants
- stimulate cell division
- control senescence (when leaves drop)
- induce flower formation
- enhance fruit ripening
- response to pathogens
- sense and respond to stress
- sense and respond to light and gravity
99
What are the four major plant hormones
- auxin (IAA)
- gibberellins (GA)
- Abscisic acid (ABA)
- Ethylene
100
What are four ways hormone study can be performed?
- Measure concentration (correlate certain hormones with timing of processes)
- Addition (add hormone and see response)
- Mutant (modify plant in some way)
- Fluorescent or radioactivelabelling
101
What are the four steps of action in hormones?
1 - Cue
2 - Hormone is synthesized or activated
3 - Hormone binds to receptors to initiate response
4 - final effect - synthesis of compund, cell division, movement, etc.
102
What do auxins do?
Accumulate on dark side of stem, causing early elongation, causing bending of stem towards the light
103
What does gibberellins do
Causes shoot elongation
- GAs focuses less emergy on stems, more on growing grains
104
What is "anti-gibberellins"?
Hormones used in nursery industry to prevent stem elongation and make plants more compact, reducing need for pruning
105
What is abscisic acid?
Accumulates in response to dehydration stress
- Plant can't wait for leaves to wilt to have a response
- Plants sense low water potential in roots, produces ABA and transports to shoot
Addition of ABA causes plants to close their stomata to conserve water
106
What is ethylene?
Hormones act by inducing gene transcription, activity of enzymes or transporters
- coordinates fruit production, inducing ripening
- Ethylene inhibitors prolong flower pife
107
Give two examples of how organisms hijack plant hormones
- oak bacterial pathogen inserts genes directly into host plant genome, enconding auxin and cytokines
- insects burrow in goldenrod and secrete IA which stimulates cell division
108
What is crosstalk?
When two hormones are not independent, can be additive (synergistic), or negative (antagonistic)
109
What is apical dominance?
When apical buds inhibit the growht of auxiliary buds further down the stem
- This allows the plants to grow vertically and compete for light
- Occurs via auxin produced in the apical bud
- When apical bud is removed, auxin suppression is removed
110
In what ways can a toxic plant maintain reproduction?
- Pollinate be deceit (imitate rewards)
- Wind pollinated
- Provide non-nectar reward (shelter, pollen, heat...)
- Pollinate by animal that are not impacted by toxin
- Avoid sexual reproduction - selfing
