Final Flashcards
What produces Gibberellins
all plants; most fungi do not
Majority of Gibberellic acids are either:
intermediated in the biosynthetic pathway
breakdown/inactivation products
Which four GAs are considered physiologically active?
GA1, GA3, GA4, and GA7
Where is GA produced?
produced in younger tissues and exported via phloem
Gibberellins are well-known for …
promoting plant stem elongation
How do GAs function?
By regulating gene transcription
What is the role of DELLA in reference to GAs?
DELLA proteins act as growth repressors by inhibiting GA signaling in response to developmental and environmental cues.
GID1 is what
Gibberellin receptor; found in the nucleus and cytosol
Why was the semi-dwarf trait less susceptible to lodging?
The stems were shorter and stronger
In wheat and maize, the semi-dwarf trait was due to …
a mutation in DELLA
True or False: GAs are involved in flowering
True
the starch in endosperm is broken down by
Amylases (hydrolytic enzymes)
The two main methods for plant tissue culture is:
callus culture = small chunks of non-differentiated plant tissue on agar
suspension culture = smaller chucks in a liquid medium
True or false: a good source of cytokinins was coconut milk
true
Kinetin is a plant hormone; true or false
false; Kinetin is a plant growth regulator
Kinetin is a product of
oxidative damage of adenine
Cytokinins is synthesized where?
The roots and sites of cell division (eg. the vascular cambium)
Cytokinins have a role in … (2)
regulating cell division, and regulating apical dominance
Plant Gall disease is due to…
due to bacterial production of cytokinins and auxins
3 steps of genetic modification/transformation using the Ti plasmid
- Insertion of gene into plasmid using restriction enzyme and DNA ligase
- Introduction into plant cells in culture
- Regeneration of plant
Cytokinins affect senescence how?
It delays it, senescence is the aging process
The CK receptor is found where?
In the ER (endoplasmic reticulum)
The CK receptor does what?
Signals transduction pathway
Regulation of transcription
Ethylene is primarly associated with:
stress responses
senescence
fruit ripening
True or false: Senescence and ripening have nothing in common
false
The ethylene-induced “triple response” in plant seedlings is:
1) decrease stem elongation
2) increased stem radial growth
3) prevention of opening of the “hook” at the top of the seedling
What is the best-known ethylene effect
stimulation of ripening in climacteric fruits (i.e apples, bananas, avocados, tomatoes)
Stages of fruit development
Cell division, cell expansion, maturation, ripening, senescence
Non-climacteric fruits require ethylene to ripen. True or false?
False
Sequence of events in climacteric fruits
- ethylene production
- an increase in respiration rate
- increased ACC synthase activity
- increased ethylene production and synthesis of degrative enzymes
The softening of the cell wall in fruit ripening is due to:
an increased activity of several enzymes; like pectinase
Soil with air spaces are better than water-saturated soil. True or false
True.
The results of increased radial growth due to ethylene is:
stem thickening
The hook of a stem acts as
protection for the apex of the shoot
In most plants ethylene inhibits flowering. True or false
true
Pollination increases ACC synthesis; what is the affect of this
Leads to earlier senescence
Flavr Savr tomato used what gene is used to keep it firmer longer
Antisense polygalacturonase gene
Why do Tomatoes on the vine last longer than ones off the vine?
it reduces ethylene leakage
Abscisic Acid is known as the…
stress hormone
Abscission is …
the shedding of plant parts after formation of an abscission zone
What are the roles of abscisic acid?
Stomatal closure
Hardening
All photosynthetic eukaryotic organisms use which type of photosynthesis
light-dependent oxygenic CO2 fixation
Light-dependent means…
light is required for this part of the process
Oxygenic means …
that O2 is produced
CO2 fixation means …
that CO2 (inorganic C) is converted to organic C
What is the source of electrons for photosynthesis?
Water
O2 plays an important role in photosynthesis; true or false
false, it is simply a biproduct of the reaction.
What are the end-products of photosynthesis?
Starch and sucrose
How many electrons are needed in order to reduce one inorganic carbon to an organic carbon
4 electrons or 2 water molecules
The light reactions of photosynthesis are _____ - insensitive
relatively temperature
The enzymatic reactions of photosynthesis are temperature _______
sensitive
Photosynthesis is divided into two reactions known as:
The light reactions and the enzymatic reactions
The light reactions occur where?
Chloroplast, and thylakoid membranes
The enzymatic reactions occur where?
Chloroplast and stroma
Stacks of thylakoids are called …
grana (granum)
All of the pigments are in the chloroplast, True or false
false, they are locating in the thylakoids
The energy source for photosynthesis is …
light
The two major types of pigments are:
Chlorophylls (which are green)
Carotenoids (which are red-orange-yellow)
_____ have no OH groups
Carotenes
________ have OH groups
xanthophylls
The most important function of carotenoids is …
photoprotection (they detoxify toxic molecules)
Particles of light are measured in
photons or quanta
Most common definition of Photosynthetically Active Radiation (PAR)
400nm to 700nm
Units for PAR
umol quanta m^-2 s^-1
Photosynthetic pigments have characteristic absorbance spectra, which means?
The ability to absorb various wavelengths of light
Action Spectra is
the wavelength that can be used for a particular process
Absorption of a photon leads to the movement of an electron to higher energy orbital. True or false
true
What are the two photons that result in the lowest excited states?
red and blue
Antenna complexes are
groups of pigments that are associated with a reaction centre Chl
Antenna complexes funnel ____/____/____ towards the reaction centre
energy; excitation; exciton
the light reactions are the parts of photosynthesis that are directly light-dependent. These include:
- Absorption of photons by photosynthetic pigments
- transfer of energy of the photons to the reaction centre chlorophylls
- photosynthetic electron transport chain (which creates a delta [H+] across the thylakoid and also produces NADPH)
- utilization of the delta [H+] by ATP synthase to regenerate ATP
The process of light reaction photosynthesis is happening where?
in the thylakoids and across the thylakoids
The products of the light reactions are
NADPH and ATP
The enzymatic reactions include these cycles:
Calvin cycle (in the stroma), Starch synthesis (stroma) and sucrose synthesis (cytosol)
Which part of photosynthesis is not located in the chloroplast?
Sucrose synthesis
the products of the enzymatic reactions include:
starch and sucrose
In the light reactions, the pigment trap light energy. This trapped energy is used for two purposes:
- generate a [H+] gradient across the thylakoid membrane
- regenerate NADPH for use in the enzymatic reactions
A photosystem consists of …
a reaction centre complex and light-harvesting complexes
The light-harvesting complexes have no electron carriers in it. true or false
true
reaction centre chlorophylls have three possible states, and cycle through them; these states are …
ground state ; excited state ; oxidized state (= loss of an e-)
OEC means
oxygen-evolving complex
The OEC catalyzes the _________-________ ______
water-splitting reaction
In PSII, how many photons are needed to produce one oxygen
4
There are two sources of PQH2 in the photosynthetic electron transport chain. These come from?
PSII
Cytochrome complex
For every PQH2 that leaves the PSII, how many and what is moved from the stroma to the lumen
4 H+
There is a plastocyanin (PC) pool in the lumen. True or false
true
8 photons, (4 in PSII and 4 in PSI) are sufficient to meet which requirements?
a) ATP
b) NADPH
c) FNR
d) H+
b) NADPH
Delta [H+] has two sources in photosynthesis, these come from where?
OEC
Cyt complex/Q cycle
How many ATPs are required to fix each CO2 in photosynthesis?
3 ATP
8 Photons is sufficient enough to meet the requirements of both NADPH and ATP for fixing 1 CO2 molecule. True or False
False, 8 photons is enough for NADPH to fix 1 CO2 molecule, but does not meet the requirements for ATP
LEF
Linear electron flow
The LEF is …
Water -> PSII -> PSI -> NADPH
CEF
Cyclic electron flow
The CEF is …
PSI -> PQ pool -> cyt complex -> PC -> PSI
What is the best solution to creating more ATP without creating NADPH?
a) LEF
b) PQ
c) CEF
d) Cyt complex
c) CEF
Why is C3 photosynthesis called C3?
Because the first stable products of photosynthesis are 3 C molecules
C3 species represent what percentage of terrestrial plant species?
85-90%
The phosphate translocator is also known as …
the triose phosphate translocator (TPT)
Plant priorities for the Calvin cycle are (3 steps)
- build up the levels of the calvin cycle intermediated especially RuBP
- Start drawing off TP from the calvin cycle, for sucrose synthesis and export
- Starch synthesis - lowest priority, starch is temporary energy
The Calvin cycle uses the products of which reaction to assimilate inorganic C into organic C?
Light reactions
The phosphate translocator links _____ _______ ______ with ____ ______ _________
Stromal photosynthetic metabolism ; cytosolic sucrose synthesis
At what time of day is the chloroplast starch broken down and converted into sucrose?
At night
What is the Warburg Effect?
the O2 inhibition of photosynthesis; the higher the [O2], the lower the rate of net photosynthesis
The gross photosynthetic rate is …
the rate of O2 production by the OEC or the rate of CO2 uptake/fixation by Rubisco
Net O2 evolution is
gross O2 evolution (from OEC) minus processes that consume O2
Net CO2 fixation is
gross CO2 uptake (rubisco) minus processes that release CO2
CO2 and O2 compete for the active site on ____?
a) PSI
b) Calvin Cycle
c) CEF
d) Rubisco
d) rubisco
When rubisco and O2 bind, what type of reaction occurs?
Oxygenase
When Rubisco and CO2 bind, what type of reaction occurs?
Carboxylase
Aerobic cellular respiration consumes O2 via which chain?
respiratory electron transport chain
IRGA
Infra-red gas analyzers
What are IRGAs able to do?
Quantify [CO2] in air
CO2 can absorb certain IR wavelengths. True or False
True
Net Photosynthesis is how much C a plant gains in photosynthesis. What is the equation associated with this?
Net photosynthesis = gross photosynthesis - respiration - photorespiration
Photorespiration is respiration :) true or false
FALSE
Photorespiration is considered to be energetically wasteful because:
- generates inorganic carbon (CO2) from organic carbon (i.e. it undoes photosynthesis)
- generates inorganic nitrogen (NH4+) from organic nitrogen, and the NH4+ must be re-assimilated into organic form in an energy-requiring process
How old is rubisco
about 3 billion years old
C4 plant species make up what percentage of terrestrial plants?
3-5%
CAM
Crassulacean Acid Metabolism
CAM take up what percentage of terrestrial species
5-10%
Both C4 and CAM posses the Calvin Cycle. True or false
true
Kranz means
wreath
Which type of species uses Kranz anatomy
C4
Describe Kranz anatomy
A vascular bundle (xylem and phloem) center, surrounded by bundle sheath cells (rubisco) which is subsequentially surrounded by mesophyll cells (PEPcase)
The calvin cycle only occurs in which cells of C4 plants
a) Mesophyll cells
b) Bundle sheath cells
c) Temporal cells
d) Malate cells
b) bundle sheath cells
In C4 photosynthesis, the reaction catalyzed by pyruvate, phosphate dikinase (PPDK) consumes the equivalent of how many ATP molecules?
two
Mesophyll cells utilize the Calvin Cycle, True or False
false, but they do use other components of photosynthesis
Water Use Efficiency has what equation
WUE = (carbon gained in photosynthesis) / (water lost in transpiration)
WUE is also known as the “photosynthesis-transpiration compromise”; what are the two ways to look at this?
- For a given net photosynthesis rate, C4 species have a lower g(s)
- For a given g(s), C4 species have a higher net photosynthesis rate
C4 species tend to be found mostly where?
warm semi-arid regions
C4 have a higher WUE than C3 species. True or False
True
What type of leaves/stems do most CAM species have?
Succulent
What happens to stomates in CAM species?
The are open at night and closed during the day
Stage 1 of CAM photosynthesis includes:
malate accumulates in the vacuole at night
stomates are open at night
CO2 diffuses into the mesophyll cells of the leaves
PEP is produced from starch breakdown and glycolysis
Stage 2 of CAM photosynthesis includes:
during the day time; malate levels decline
stomates are closed to save water
Malic enzyme decarboxylates malate to produce CO2
CAM is considered to be the most expensive mode of terrestrial photosynthesis; why (3)?
- costs of regenerating PEP from pyruvate (PPDK)
- starch re-synthesis costs from PEP (PEP ->->-> starch)
- ATP costs associated with malate transport across the tonoplast
Nitrogen is the second most important nutrient for plant growth. True or false
False, it the the most important
The two best known and most studied forms of N taken up by plant roots from the soil solution are:
NO3- (nitrate) and NH4+ (ammonium)
Urea is a form of organic N; where does urea come from?
Urine
What is the #1 form of inorganic N in aerobic soils?
NO3-
Denitrification is
Microbial reduction of NO3- to various gaseous N forms;
done by various anaerobic bacteria;
use NO3- as a final electron acceptor for respiration
Characteristics of NH4+
a cation; part of the cation exchange capacity of the soil; tends to be retained in the soil
Characteristics of NO3-
found mostly in the soil solution; more easily leached from soil
The natural input of N to a system is via the …
biological N2 fixation
Biological N2 fixation represents an ____ (input or output) of N to a system
input
The enzyme nitrogenase is exclusively a _______ enzyme
a) eukaryotic
b) prokaryotic
c) nitrogenase
d) ammonia
b) prokaryotic
Nitrogenase is a very O2-labile enzyme, thus it requires a _________________ environment in order to function
Anaerobic or microaerobic
The symbiotic bacteria in legumes is known as
rhizobia
The symbiosis occurs in vesicles in “infected” cells are known as
symbiosomes
The membrane of the symbiosome is sometimes called the …
peribacteroid membrane
Biological Nitrogen Fixation in Legume Nodules can be summarized as …
sucrose in, amino acids out
Leghemoglobin is
a pink-coloured O2-binding molecule found in the central portion of legume nodules
What is the function of leghemoglobin?
to regulate [O2] in the central portion of the nodule (where the bacteroids are located)
Leghemoglobin maintains in what type of environment?
Microaerobic
The outer layer of the leghemoglobin functions as
an O2 diffusion barrier
N sufficiency leads to
decreased nitrogenase activity
N2 fixation is response to N deficiency. True or false
True
Cyanobacteria
blue-green algae
Nitrogen in plant cells are located in:
proteins/amino acids
RNA
DNA
chlorophyll
ATP
etc
Both nitrate and ammonium transport systems exhibit
substrate-induction
Nitrate is _____ charged and must cross the plasma membrane to the ______ -charged area
negatively x2
Most ammonium transporters are…
uniports
Ammonium is directly assimilated into…
amino acids
Nitrate is not toxic at high concentrations; therefore plant cells may contain …
high levels of nitrate (typically stored in vacuoles)
The enzymes for nitrate reduction to ammonium are found in …
both roots and shoots
Different species do most of their nitrate ______ in either roots or shoots
assimilation
Nitrate that is taken up by roots may be: (3)
- assimilated into organic nitrogen in the root, which is then redistributed via phloem
- stored in root vacuoles
- sent to the shoot via xylem after which it may be stored in leaf vacuoles or assimilated into organic nitrogen via NH4+
Nitrate must be reduced into ____ in order for subsequent assimilation into ____
NH4+ ; organic N
Simple version of Nitrate reductase
(NO3-) + (2e-) -> (NO2-)
What energy does the GS-GOGAT Pathway require?
ATP and NADPH
The product of the GS-GOGAT pathway is
the amino acid glutamate
Ammonium represses nitrate assimilation by repressing the …
transcription of nitrate reductase
What order (from cheapest to most expensive) are the forms of inorganic N sources? (N2, NH4+ and NO3-)
NH4+
NO3-
N2
When a plant cell is pressurized, it exhibits what
turgor
Main Components of primary plant cell wall are: (4)
cellulose microfibrils
hemicelluloses
pectin
a small amount of proteins
Cellulose chains are responsible for what
strength and rigidity of the cell wall
Cellulose microfibrils have two different orientations:
Criss-cross pattern and Parallel
Hemicelluloses function to
cross-link adjacent microfibrils
The idea of cross-linking affects what part of the cell
cell wall rigidity
Pectin acts as
the glue between adjacent plant cells
Lignin adds…
strength to cell walls; only found in cells with primary and secondary walls
True or False; Wood has a high lignin content
True
Light-dependent oxygenic CO2 was invented by (thing ; not person)
Cyanobacteria
Cyanobacteria are gram-________
negative
Name the membrane enclosed organelles
nucleus, chloroplasts, mitochondria, vacuoles, endoplasmic reticulum, Golgi apparatus, peroxisomes
Types of permeable membranes
Semi, selectively, and differentially
Phospholipid bilayers have a
hydrophobic core and hydrophilic surfaces
Carrier Proteins
are transport proteins with substrate-specific binding sites
Channel proteins
are transport proteins that allow specific molecules to pass
Aquaporins
are membrane-spanning proteins that act as moderately selective water channels
DNA of plants cells can be found where?
Nucleus, plastids, and mitochondria
Main purpose of Ribosomes
produce proteins (via translation)
Chloroplasts are the site of what
photosynthesis
Chloroplasts are descended from
Symbiotic cyanobacteria
Chromoplasts are descended from
chloroplasts
The vacuole plays a role in what
water relations, as a storage area for ions, and the location of anthocyanins
The membrane that surrounds the vacuole is called the
tonoplast
The interior of the vacuole is not acidic. True or false
False; it is slightly acidic
Plasmodesmata are
cytosolic connections to adjacent plant cells
Diffusion of molecules through the plasmodesmata is regulated by
desmosomes
Mitochondria are the site of
aerobic cellular respiration; which functions to regenerate ATP
Golgi Apparatus is involved in
protein modification and protein sorting
The endoplasmic reticulum is
a membrane network that runs through the cytosol
Rough ER has what, and is involved in what
Ribosomes; and is involved in protein synthesis
Smooth ER has roles in
cellular metabolism
Peroxisomes are involved in
photorespiration
Glyoxysomes are involved in
fat breakdown
Protein bodies are
protein storage organelles
Cytosol is
the water-based gel-like fluid in which the organelles are found; this is an active site of metabolism
Cytoplasm includes
the cytosol and the cytosolic ribosomes and the cytoskeleton
protoplasm is
everything inside the plasma membrane
Transpiration
loss of water vapour from plants
Evaporation + Transpiration =
Evapotranspiration
of the water that is transpired, the bulk is via ___________ on the leaves
stomates
What percentage of light energy impinged upon plants is used for photosynthesis?
less than 1%
In plants, water has 3 physiological importances
Medium for biochemical reactions; maintenance of turgor; and temperature regulation
Two mechanisms for the movement of water:
Bulk flow, and diffusion
Bulk flow:
mass movement of water in response to a pressure differential (from high to low; ie down a pressure gradient)
Water movement: Diffusion means
net movement due to random kinetic activities or thermal motions
Diffusion of Solutes can occur in response to
gradients of solute concentraion
Net diffusion of solutes occurs from….
area of higher concentration to areas of lower concentration
The larger the concentration gradient, the greater the rate of diffusion; true or false.
True
What happens at equilibrium for diffusion of solutes
no net movement; but still gross movement
The higher the concentration of a substance…..
the greater its chemical potential
Osmosis
the diffusion of a solvent such as water across a semi-permeable membrane separating two solutions of different concentrations
Water Potential (greek letter psi)
the chemical potential of water in a system, compared with the chemical potential of pure water at atm
dissolving a solute in water _______ the chemical potential (Ψ) of the water
decreases
What is the maximum water potential
0MPa
Water with any dissolved solute will have a Ψ _ 0MPa (<, >, =)
<
What happens to Ψ the greater the [solute]
the lower it becomes (ie more negative)
[Solute] outside > [solute]inside
hypertonic solution
[solute]outside = [solute]inside
isotonic solution (usual state)
[solute]outside < [solute]inside
hypotonic solution
ΨS is
Solute potential; the effect of solutes on water potential; always negative
Raoult’s Law
the vapour pressure over perfect solutions is proportional to the mole fraction of the solvent
ΨP
pressure potential; is not affected by [solute]
In general, Ψp= AP - 0.1013MPa; true or false
true
Ψ equation
Ψs+Ψp
water relations of the idealized cell has (2)
- extremely rigid cell wall
- a PM that is perfectly selectively permeable
water relations of a less idealized cell has (2)
- cell wall that has some extensibility
- a PM that is perfectly selectively permeable
As water flows into a cell following a Ψs gradient, 3 things happen
- water movement into the cells causes an increase in CellΨp
- The cell wall stretches in response to the increased turgor
- the water dilutes the solute, increasing Ψs
What happens if CellΨs < Ψs outside the cell?
Plasmolysis happens; the PM pulls away from the cell wall and the protoplasm shrinks
How do cells take up water?
for net water uptake Ψroot < Ψsoil
In order to maintain ΔΨ in the correct direction, plants can increase their internal [solute]; this process is called
osmotic adjustment or osmoregulation
Compatible solutes are _______ ________ for a plant to produce
energetically expensive
three hypotheses for moving water upwards
- suction
- root pressure
- Capillarity
Current model of moving water upwards
Cohesion-Tension Theory; liquid water is pulled up a plant, in a continuous stream, via evaporation from cell walls within the leaf
Three main elements of the Cohesion-Tension Theory
- ΔΨ between the soil and atm is the driving force
- adhesion/hydration
- cohesion
Driving force for water movement through a plant?
SPAC soil-plant-atmosphere-continuum; water uptake and transpiration are parts of one continuous stream or process
Vascular plants have vascular tissue; which are…
the xylem and the phloem
When water and dissolved inorganic ions move, they move through what?
the xylem
“Wood” of a tree or shrub is comprised of
xylem
The older xylem is called
heartwood
The younger xylem is called
sapwood
Sapwood is responsible for
the bulk of water
Xylem of woody eudicots consists of four types of cells:
- tracheids
- vessel elements
- xylem fibres
- radial (rays) and axial parenchyma cells
In woody plants, new xylem is produced every year by the…
vascular cambium (a secondary meristem)
the cork cambium produces…
the bark
Phloem accumulates in woody plants; true or false
false; the xylem accumulates
Xylem fibres play a structure role in the…
stem
Tracheids are…
the water conducting cells
How does water move in conifers?
Via the tracheids; they do not have vessel elements or xylem fibres
At maturity, are each of the following dead or alive:
Trachieds
Vessel elements
Fibres
dead
dead
both
Vessel elements have this that links adjacent vessel elements
perforation plates ( looks like a fork thingy)
Living, undifferentiated cells are known as
parenchyma
Rays (in water) are composed of
parenchyma
Vascular rays are probably involved in what
the refilling of xylem elements
The vascular bundles make up the ______ in a leaf
veins
What is the primary site of water uptake?
Roots
Root hairs are…
extensions of epidermal cells
Fine roots have what ratio
high surface area : volume ratio
Root apical meristem (RAM) is
a zone of cell division
Root growth is due to:
cell division followed by cell elongation
Apoplast
the non-living part of the root; includes air spaces, cell walls and xylem
Symplast
the living part of the root; including everything inside the PM
The Casparian strip is
an extracellular water barrier
Apoplastic water movement is along
the hydrated cell walls
Symplastic water movement
is cell-to-cell, via plasmodesmata
All water molecules must cross a PM twice, why?
- to get into the symplast
- to leave the symplast at the xylem
What is the purpose of the endodermis?
it is a mechanism for the plant to control water movement to the xylem
Is the Ψs high or low in the xylem
very high (=not very negative)
Why are smaller diameter vessels less prone to cavitation?
cavitation seems to begin at surfaces; ie smaller tubes have a better surface/volume ratio
In water movement, why does it help if stomates are open?
It provides a diffusion pathway
The xylem is a part of the apoplast, but gets its water from the symplast; true or false
true
Summary of the Tension-Cohesion Model
- Water has high cohesive forces
- water in plants forms a continuous system through water-saturated cell walls
- reduction in water potential at the evaporating surfaces is transmitted to the roots, causing inflow of water from soil
Bordered pits act as _____ _____ that prevent air bubbles from spreading
safety valves
Guard cells occur in, and do what
pairs; and regulate the size of the stomatal pore
Guard cells differ from standard epidermal cells: (3)
- not covered by the cuticle
- they have chloroplasts
- they lack plasmodesmata
Stomates consist of
the pair of guard cells and the pore between the guard cells
In eudicot leaves, where are the stomates located
on the underside of the leaf
In monocots, where are the stomates located
both sides of the leaf
Stomates mediate….
the photosynthesis-transpiration compromise
Photosynthesis has a _____ water cost
a) slow
b) high
c) low
d) fast
b) high
Boundary layer is…
an unstirred layer of air that is around all objects
The boundary layer represents a
resistance to diffusion of gases
Three factors that affect boundary layer conductance/resistance
leaf size, leaf shape, wind speed
What are two ways to increase boundary layer depth
having stomates in crypts, and leaf pubescence
Stomatal conductance (gs) is under the direct control of
the plant
Changes in gs are caused by…
the guard cells changing shape
Guard cells are said to integrate what
environmental signals
What are 4 main signals that promote stomatal opening:
light (PAR)
blue light
low internal [CO2]
high external PH2O(g)
Signals that promote stomatal closure
- darkness
- water stress
Severe water stress will lead to
complete stomatal closure, no matter what other signals are being observed
Water stress override is mediated by what plant hormone
Abscisic Acid (ABA); this hormone lets the guard cells know to close the stomate
Two signals lead to elevated [ABA] in the guard cells:
- loss of leaf cell turgor
- loss of turgor in fine roots lead to the production of peptide signal
Stomatal opening is based on
water relations
As Ψp increases, the guard cells lengthen; meaning…
the pore opens
Blue light is detected by
guard cell phototropin; this initiated a signal transduction pathway
Activation of the H+-ATPase results in
hyperpolarization of the plasma membrane
Hyperpolarization activates what type of channel
Voltage-gated K+ channels on the plasma membrane
K+ is balanced by which two anions
Cl-, and malate 2-
PEP comes from…
starch breakdown (glucose -> glycolysis)
When stomates close, H+-ATPase activity decreases, which three solutes leave the cell
K+
Cl-
Malate 2-
Girdling
removing a strip of bark all the way around a tree. Removes material all the way to the xylem
Girdling leads to
swelling above the girdle and shrinkage below the girdle
Is phloem alive or dead at maturity?
alive
Sieve elements are the
major conducting cells in phloem
Companion cells are responsible for
loading solute into the sieve element
The source for photosynthate is
mature leaves or almost mature leaves
Sinks for photosynthate include (3)
roots, developing leaves, developing fruits
Sinks for organic N include
developing leaves, developing fruits, roots
How many rounds of cell division does it take for the formation of sieve elements and companion cells
1
Cell division occurs in zones called
meristems
the vascular cambium is also a site of cell division; true or false
true
Younger leaves and internodes will exhibit ____ ________
cell expansion
The growth rate of an individual cell is controlled by what two important factors:
1) Wall extensibility
2) yield threshold
Expansins are
small non-enzymatic proteins that break the bonds of hemicelluloses and cellulose
Photoreceptors are
pigments that absorb light for the use in a physiological process
Phytochromes are
a class of photoreceptor
Phytochromes act as dimers, each dimer has
a chromophore (light-absorbing) attached to a protein
Pr means
red light absorbing phytochrome
Pfr means
far red light absorbing phytochrome
Pfr can absorb
both red light and far red light
Pfr can promote and inhibit a particular process. true or false
true
Short day plants (SDPs) have
a maximum light period, beyond which flowering will not happen
Long day plants (LDPs) have
a minimum light period, which must be exceeded for flowering
Day Neutral plants have
no effect of photoperiod on flowering
The last night break will always determine flowering; which break promotes this flowering?
Far red
Which type of light promotes seed germination
red
Red light and blue light do what to stem elongation
inhibit it
Far red light does what to stem elongation
promotes
High Pfr:Pr indicates what
the plant is shaded or you have neighbours, GROW BIGGER (elongate stem to avoid competition)
Phytochrome-interacting factors (PIFs) are transcription factors that are
regulatory proteins that bind to promoters of genes
Cryptochromes are
receptors for blue light and UV-A
Cryptochromes are involved in (3)
blue-light mediated inhibition of stem elongation
blue-light mediated promotion of leaf
setting of the biological clock
Phototropin
is a plant blue light and UV-A receptor
UV_B is the trigger for what kind of production
anthocyanin
two important commonalities between plants and animals in regards to hormones
- must have a receptor
- has a signal transduction pathways
Plants have one specific hormone-producing organ; true or false
false; plant hormones are often transported but can have an effect on the organ they were produced in
Most hormone effects are due to the interactions of 2+ different hormones; this generality is typically called
cross-talk
Which type of tissue tends to produce more hormones? (Older or younger)
Younger
Five well-known classes of plant hormones are
Auxin
Gibberellins
Cytokinins
Ethylene
Abscisic Acid
What was the first plant hormone to be discovered?
Auxin
What is a coleoptile?
a hollow sheath in the seedlings of grasses and some other monocots
Auxin is responsible for
promoting elongation growth
Auxin is synthesized in the
coleoptile tip
Auxin is redistributed towards…
the dark side and moves down the seedling
Indoleacetic Acid (IAA)
the major auxin in all plants
Shoot-derived auxin regulates
secondary root production
externally applied auxins promote
adventitious root formation on stems
Apical dominance
suppression of axillary bud growth by apical bud/apical meristem (plants grow tall, not wide)
What are two things that auxin stimulates
H+-ATPase activity; and transcription
Which model is known for auxin transport
chemiosmotic-polar diffusion model
Auxin is transported via
the vascular parenchyma cells
What are some examples of amendments
plant ash, lime, or organic material
amendments are known to (benefit of….)
increase crop yield
Elements found in plants were often not a reflection of what was in the soil; true or false
false, it is a reflection of what is in the soil
two criteria of plant mineral nutrition identification
- the species in questions must be unable to complete its life cycle in the absence of the element
- the function of the element cannot be replaceable by another element
How many elements are known to be essential for plants?
17
The three most common essential elements are…
C, H, O
Many Halophytes grow better in the presence of high levels of
Na+
Rice and Horsetails grow better in the presence of
Si
Legumes indirectly benefits from the presence of
Co 2+
Mineral element uptake by roots can be called
solution mining
How many different nitrate transporters are there in roots of Arabidopsis
about 5
Luxury consumption
many of the macronutrients may be taken up far in excess of what is needed for growth
“Hidden hunger” means
that the plant is not displaying visual deficiency symptoms
Excessive nutrients can cause
toxicity and reduced yield
Two possible mechanism for metal toxicity
- high concentrations of metals in the soil solutions
- metal can hitch a ride on other transport systems
Soil can be defined as
rock and organic matter on their way to the ocean
Five compartment/fraction model includes:
1) non-exchangeable
2) soluble
3) exchangeable
4) plant material
5) dead organic matter
Litter
minerals become available after microbial breakdown of complex organic molecules
Humus
composed of humic acids; top of soil horizon - large part of the soil
Soluble fraction
the mineral nutrients that are dissolved in the soil solution
soluble fraction contains a portion of the ______ and the majority of the ______ except for phosphate
cations; anions
Exchangeable fraction
soil has negative charges -> attracts cations
equilibrium between soluble and exchangeable minerals
Cation exchange capacity
the ability of a soil to bind cations
Loam
approx. equal amounts of sand, silt, and clay - or 40:40:20
Silt
intermediate sized soil particles; smaller than sand, larger than clay
Availability of cations in the soil solution depends upon the
strength of adsorption to the soil
the stronger the adsorption, the less available for uptake by roots, which also means
more resistant to leaching
Soil cation concentrations are said to be “buffered” meaning
as cations are taken from the soil solution by plant roots (or lost by leaching) can be replaced by cations from soil particles
What are some approaches of trying to identify limiting nutrients?
- soil analysis
- visual diagnosis
- Plant analysis
- Experiment approach
Chlorosis
yellowing of the leaves
necrosis
localized death (brown areas)
Complications of visual diagnosis of mineral nutrient deficiencies:
- species-specific differences
- different deficiencies can lead to similar symptoms
- excess nutrients can lead to toxicity symptoms
- chlorosis and necrosis are also associated with infection
What will looking for evidence of re-mobilization show you? (mineral nutrient deficiency)
it won’t tell you what the deficiency is, but will tell you what it is not
When determining if the element is structural or catalytic; what will it tell you about the deficiency?
Structural: can lead to developmental problems
Catalytic: leads to problems with the photosynthetic apparatus
PM of root cells are full of
transport proteins
What is the importance of the PM electrochemical gradient?
affects the costs of nutrient transport
The electrochemical gradient is the combination of
the electrical gradient and the chemical (=concentration) gradient
Three ways for mineral nutrients to come into contact with roots
- diffusion
- carried in bulk flow with water
- roots can grow towards a deposit
Root Morphology
dry weight/mass allocated to roots varies between species and environmental conditions
What is the importance of Surface Area (plant mineral nutrition)
absorption of mineral nutrients occurs across a membrane, the greater the membrane surface area, the greater area for absorption
Root turnover
produced then die
loss of roots is due to
predation by soil organisms
senescence
Soil organic matter if from
leaves and roots, and microbes that decompose the plant organic matter
Necromass
deadmass
two broad categories of mycorrhizae
ecto (outside) and edno (inside)
Mycorrhizae
fungus-roots
Ectomycorrhizae are very common in
trees
Arbuscular Mycorrhizae’s exchange site is in
the arbuscle located in the white roots
Mycoheterotrophs
plants that are described as mycorrhizal cheaters or parasites; they tap into exisiting networks for their own gain, but make no contribution
Holoparasites
have no leaves and no photosynthetic capacity; parasitic
Hemiparasites
have leaves and can do photosynthesis; parasitic
Plant movement can be divided into two broad categories:
nastic movements and tropisms
Nastic movements include
Nyctinasty
Hydronasty
Seismonasty/ Thigmonasty
Nyctinasty
leaf movement in response to day and day; controlled by both the environmental and internal biological clock
Nastic Movements are
triggered by external stimulus, but the direction of the stimulus does not determine the direction of movement
Nastic movements are driven by
pulvini; thickened zones of petioles that possess motor cells
Hydronasty
movement in response to water stress
Seismonasty/Thigmonasty
Movement due to touch or vibration
Tropisms include
Thigmotropism
Phototropism
Heliotropism/Solar tracking
Skototropism
Thigmotropism
directional response to touch
Phototropisms
growth towards the light; this growth is irreversible
Heliotropism/Solar tracking
growth towards the sun (helio) ; growth via pulvini (solar)
Skototropism
Skoto means darkness; growth towards the dark
Gravitropism
(=geotropism) - growth in response to gravity
Positive gravitropism
growth in the same direction as the gravitational froce
negative gravitropism
growth in the opposite direction to the gravitational force
Orthogravitropism
vertical growth in response to gravity
Diagravitropism
horizontal growth (gravity)
Plagiogravitropism
growth at an angle
Agravitropism
no response to gravity
Both roots and shoots exhibit gravitropism; true or false
true
If you remove the root cap, what will happen in regards to gravitropism
gravitropism disappears
Statocytes are
the cells that contain statoliths; statocytes are the site of gravity perception
What do the statoliths sink onto?
1) ER
2) Cytoskeleton
3) PM
PIN3 and PIN7 are
auxin efflux transport proteins
Stems and coleoptiles exhibit what type of gravitropism
negative gravitropism
Shoots do not have statoliths; true or false
false, they do
Circumnutation
is the rhythmical circular, bending movements of plant tips as the plants grow
Gregarious flowering
mass flowering
Circadian Rhythms
oscillate within a period of 24h
In sensitive plants, continuous darkness continues the leaf to
open and close
the mechanism to rest the circadian clock is thought to be
an environmental cue, e.g. dawn/light
Entraining
refers to the fact that biorhythm exhibits the same periodicity as the environmental fluctuation or factor
Light acts as a rest button in the leaf _____ entrainment
nyctinasty
in nyctinasty clock resetting, dawn…
advances the clock
in nyctinasty clock resetting, dusk…
delays the clock
Photoperiodism
response to daylength
Critical daylength
is the maximum daylength for flowering in an SDP or the minimum daylength for flowering in an LDP
LDs promote
stem elongation and tillering (=formation of side shoots)
SDs promote
tuber formation
Plant cold hardiness
ability to withstand low temperatures
LT means
lethal temperature
Freeze-induced electrolyte leakage
common method used for determining the cold hardiness of plant tissues
Tissue damage is associated with high conductivity because
the cells rupture and leak “electrolytes” into the water in a vial
What are two good reasons to synchronize flowering with time of year?
- in seasonally cold climates
- some species are vary dependent on outcrossing
arable land
suitable for plant-based agriculture
How did global agriculture accommodate the continuous increase in population size?
- increases in land area used for agriculture
- improvements in crop agriculture
Two main types of agricultural improvements
- higher yielding crop varieties
- high input (fertilizers and biocides) agriculture
artificial selection
keep selecting/planting the largest seeds from the crop, and you are applying selection pressure for large seeds
Green revolution
concerted global crop breeding program, focused on corn/maize, wheat, rice
Liebig’s law:
yield is determined by a minimum or limiting factor
Law of Decreasing Productivity
- yield depends on each growth factor
- the increase in yield is proportional to the different between the actual yield and the maximum yield
Optimisation of Fertilizer Application; major reasons:
- too much or too little will negatively affect yield
- expensive
- loss to the environment
- environment costs of fertilizer production/extraction
N fertilization of some sort is required for continuous reliable yields; (characteristics?)
must replace what is lost by harvesting
harvesting removes a lot of N in organic form
the higher the protein content, the great the N removal from the system
Sources of Nitrogen for Agriculture
manure, seaweed, plant ashes, dead fish, guano, growing of legumes
Saltpetre has three distinct uses
- component of gunpowder
- meat preservative
- agricultural fertilizer
endophytes are
microbes that live within plant tissues
GMO
genetically modified organisms
Downsides to GMOs
- human health concerns
- Glyphosate-resistant weed (gene flow, natural solection)
Bt-modified crops
Bacillus thuringiensis; produces three different groups of proteins that are insecticidal against different insect groups,
Dead zones are due to nutrient pollution such as:
sewage, animal waste, fertilizer run off
How to improve crop productivity?
continuation of plant breeding programs; decrease the loss of crops due to pathogens and pests
What are two approaches for developing salt-tolerant crops
- look for wild relatives that have greater salt tolerance to crops
- genetically modify exisitng crops
Suggested benefits of organic farming:
- less use of fertilizers
- fewer off-target effects of biocides
- fewer environmental problems from spills/disposal of biocides
- lower biocide residues on food
How productive is organic farming?
general consensus is that organic methods provide lower yield than conventional high input methods
How productive is organic farming?
general consensus is that organic methods provide lower yield than conventional high input methods
Advantages of GM crops
- may have lower cost of production
- lower biocide use
- lower losses to pests
- perhaps better nutritional quality
