APS 119: Plant physiology Flashcards
define adaptation
heritable changes in genes that occurs through natural selectionn
define acclimation
changes in gene expression and metabolism - reversible and non heritable
what percentage of a plant is qater?
95%
what are four uses of water in a plant?
turgidity
photosynthetic processes
transpiration
translocation
what percentage of global rainfall is accounted for by transpiration?
40%
a single mature oak can transpire _______ liters per year. An acre of corn can transpire ______ per day
150,000 per year
15,000 per day
transpiration is u______
unidirectional
xylem transports _______ from _____ to _____-
water
root
shoot
phloem transports _____. from S____ to S____
solute
source to sink
if you look at a plant vasculature the xylem forms and _____ surronded by _______
cross shape surronded by phloem
in monocot plants phloem and xylem are found throughout the stem. where as because of the need to store ______ dicot plants have their vasculature concentrated to the _____
lignin
outside
when will root hairs form?
when there is little water avaliable
what are the four layers of the root?
epidermis - strong supporting cell layer - allows growth through soil
coretx - provides structure
endodermis - single layer of cells regulates water intake
pericycle - root development - stem cells of the root
two routes into the xylem
symplastic route - through cytoplasm - must go through membranes
apoplastic route - though the cell walls
what is the function of the casparian strip?
in the endodermis
- cell membranes used to remove heavy metals - act as a filter
- casparian strip forces water into the symplastic route and hence enables removal of heavy metals
- prevents uncontrolled movement of water
how many types of aqua porins do humans have and arabidopsis
humans - 4
arabidopsis - 35
when is water loss heighest
photosynthesising, warm dry and windy conditions
describe cohesion tension theory
water molecules stick together by hydrogen bonding
forms a continuous column
loss from leaves pulls water up from xylem
where are boreal forests found?
a circumpolar belt northen hemisphere above 50 degrees north.
describe what happens when water freezes in the xylem of trees
dissolved gases form bubbles and are squeezed out
repeated freeze thawing creates larger bubbles
disrupts hydrogen bonding causes an embolism/ cavitation
water is no longer pulled up the xylem
how do trees tackle the problem of embolisms in freezing environments?
very narrow xylem - less vulnerable to embolism but means the tree grows slower
how did trees response to freezing evolve?
linked to drought tolerance
druier further north
focring water out of very dry soil can lead to bubbles
- gives the trees the gnetic toolbox to deal with the same problem of embolisms when freezing
photosynthesis is the basis for ____% of life on earth
99
how much CO2 is taken in by plants per year, and what is the anthropogenic emission value?
120Gt from plants
9Gt from anthropogenic emissions
when did photosynthesis evolve? what was different about this phptpsynthesis?
- 8 billion years ago
- used other molecules than water
three lines of evidence for when oxygenic photosynthesis arose
geology - red bands in rocks
fossil record
snowball earth
define stroma, thylakoids and grana
stroma = space in chloroplast with a suitable pH for calvin cycle thylakoids = electron transport chain and ATP synthase grana = stack og thylakoids
describe the process of the light dependant reaction
light hits the light harvesting complex of PSII and hits the chlorophyll molecules - energy bounced and hits the reaction centre complex. reaction centre = P680
electron in reaction centre is excited. passed on to pheophytin
water is split to produce 2 for protons and 4 electrons (per two molecules of H2O) 4 photons needed for a molecule of oxygen
electron moves from phenophytin to plastoquione
then to cytochrome b6F
plastocyanin
PSI - P700 reaction complex takes electron from plastocyanin - reaction complex met
- light re excites electron and it is passed to gerredoxin
- ferredoxin NADP reductase forms NADPH
which two proteins in the etc pump protons into the thylakoid lumen
plastoquinone and cytochrome b6F
how does cyclic electron transport work?
electron passed though PSI
ferrodixin passes electron back to cytochrome b6F
- no NADPH produced but ATP is produced
mutants that dont do cyclic electron transport dont do as well as those that do
for 2 H2O you recieve how many NADPH and ATP
4 ATP and 2 NADPH
what is an alternative na,me for the calvin cycle
calvin benson bassham cycle
what is the key enzyme envolved in the light independant reaction of photosynthesis?
RuBisCo
- adds CO2 to a C5 sugar
what are the three key processes of the calvin cycle
CO2 fixtation
reduction of organic molecule
regeneration of ribulose bisphosphate
describe the calcin cycle
RuBisco adds CO2 to ribulose 1,5 - bisphosphate. makes two lots of 3-phosphoglycerate
phosphate added to make 1,3-bisphosphoglycerate, uses one ATP. NADPH used to remove a phosphate making glyceraldehyde 3 -phosphate
glyceraldehyde 3 -phosphate is transformed into ribulose 5 - phosphate. need 5 glyceraldehyde to make 3 ribulose 5- phosphate. final ATP to reform ribulose bisphosphate
3 atp and 2 nadph used per cycle and requires multiple cycles to generate its components
what is photorespiration?
RuBisCo is an oxygenase enzyme it fixes O2 onto 2 - phosphoglycloate as well as CO2
- this occurs 25% of the time in current oxygen concentrations
what are the products of photorespiration?
2 carbon molecule and 3 phosphoglycerate
what is the light compensation point?
plants do respiration - carbon is lost through respiration. the balance between carbon lostvia respiration and carbon gained by photosynthesis is the compensation point
give adaptations of the photosynthetic proces to very high light intensity
smaller, thicker leaves, less chlorophyll (paler). reduce amount of light absorbed - more PSII less light harvesting complexes
how does photosynthesis adapt in the shade
less PSII
more light harvesting complexes
what happens when the etc recieves to much light energy?
run out of reaction centres
chlorphylls have to much energy
damage the PSII
when may photoinhibition occur?
when under extreme conditions the PSII is damaged
what is the worst case scenario for dealing with extreme light intensity?
excitation energy is passed to oxygen which creates free radicals
give short term methods plants use to acclimate to excsess sunlight
disspiate excess energy as heat - non photochemical quenching
- stimulate the xanthophyll cycle
describe the xanothrophyll cycle
pigment molecules (xanthophyll)
- vioaxanthin is changed to zeaxanthin in light stress
- zeaxanthin is an antioxidant - protects lipid membranes and acts as a regulator of non photochemical quenching
what is a long term acclimation plants can do to high light intensity? what part of the plant can do this?
phenotypic plasticity
younger leaves
what is C4 an adaptation for?
avoiding photorespiration
name the intermediates between the product of photorespiration and the desired product of photosynthesis
2 phosphoglycolate glycine serine glycerate 3 - phosphoglycerate
where does the process of converting 2 phosphoglycolate into 3 - phosphoglycolate occur?
peroxisome and mitochondria
directly uses 1 ATP
produces CO2 AND NH3
- NH3 costly to remove from the cell
what is the yield loss in tonnes per year of UK wheat from photorespiration?
3 million tonnes
what three factors effect how a species will differ in its response to photorespiration
oxygen and carbon dioxide concentrationn
rubisco structure
environmental factors
what conditions favour photosynthesis over photorespiration
high CO2 concentration
low temperture (high temperture reduces RuBisCo specificity to CO2)
higher water levels - stomata dont need to be closed hence gases dont accumulate
why did inputting the RuBisCo from red alage (more efficient) not increase the plants efficeincy?
because trade off between rate and specificity
what are the four types of method to increse CO2 concentrations within plants
dissolved inorganic pump
C2
C4
CAM
describe the dissolved inorganic pump method of carbon concentration
carbon dioxide turned into carbonate ions
pumled into pyrenoid - carbnonate reverted back into CO2 in pyrenoid
describe C2 photosynthesis
40 angiosperm species
CO2 from photorespiration and shuttles back to rubsico (via a glycine pathway)
no additional ATP needed
C4 photosynthesis occurs in ___ of plants but equates to ____% of primary productivity
3
25
C4 photosynthesis concentrates carbon around rubsico by ____ times
3-10 times
give the 7 steps of the C4 pathway
CO2 outside the leaf diffuses into mesophyll cells
converted into bicarbonate ions
then oxaloacetate
then moves to chloroplast and becomes malate moves to bundle sheath to form pyruvate and CO2
CO2 goes into the calvin cycle
pyruvate is shuttled back into the chlorophyll forms phosphenopyruvate which is added to bicarbonate ions to form oxaloacetate
when is C3 photosynthesis better than C4? which means the % of C4 plants gets ______ nearer the equator
at lower temps - below 30 degrees
greater
the water us per one gram of dry matter is about _____ in C4 compared to C3
double
when did evolution of C4 photosynthesis occur
- monocts and dicots
21-35mya in monocots
15-21 mya in dicots
how many times has C4 evolved?
62 seperate times
for what percentage of the population is rice their staple grain?
50%
because genetic enginerring of crop plants is illegal how is C4 inputted into plants?
mutagenesis - bombard crops with radiation until the desired effect is produced
what is needed in a plant in order to implement C4
more bundle sheaths
vascular bundles closer together (reduce distancce CO2 must diffuse)
CAM photosynthesis is an adaptation to________
low water conditions
where is a supprising location where you might find CAm photosynthesis?
rainforest - in epiphytes - no rooting systems, high in canopy because of high tempertures water concentrationo is very low
a lack of water means ______ photo respiration
more
how can you tell by touching a plant wether or not it is CAM
CAM plants are more succulenct - more squishy
CAM covers ___% of angiosperms
7%
C4 works as a _____ seperation method, CAM is a ______ seperation
spatial
temporal
describe how CAM photosynthesis works
NIGHT stomata open and CO2 moves into the cell converted into bicarbonate ionns convert a C3 into a C4 acid, via PeP carboxylase c4 acid (malate) moved to vacuole
DAY
malate leaves vacuole and is converted into C3 by losing a CO2
is CAM more or less efficient than C4?
less
give 3 examples of facultative CAM plants
ice plant
surinam purslane
clusia minor
CAM may occur in plants that face conditions that mimic low water levels e.g.
salt stress
high light
long days
nitrogen and phosphate deficiency
why is CAM advantegous in aquatic plants?
CO2 diffusion is 10,000 times slower
_____ litres of air are required for ___ of sucrose
5000 litres of air for 1 gram
CAM is ____ more efficient in water use than C3 and C4. C4 is _____ as efficient as C3
10 times
twice
why does CAM conserve water?
at night time when the stomata are open the potential difference between water potential in the plant and the outside is much smaller than that at mid day
whole plant adaptations to low water conditons
succulence - fill leaves with water
reduced leaves - absorb enought light through stems
compact growth form - reduce surface area compared to volume
ribs - notable on cacti, areas of tissue between them that can swell up
thick cuticle - stops transpiration
surface roots - run straight out over the surface to get as much water as possible
leaf adaptations to low water conditons
thicker cutucle on leaves
regulate stomata opening
increase boundary layer e.g with leag hairs, spines, sunken stomata, sit in pits, rolled leaves
describe how stomata open
plant forces protons out of the guard cells
leads to K+ uptake in guard cells reducing water potential
diffusion occurs into the guard cells
develops a pore 5-10ym thick
CAM plants switch off their recptiveness to ______ because it can trigger the _______ to open
light
stomata
what plant hormone controls water loss prevention?
Abscisic acid
what are the three macro nutrients plalnts need?
Nitrogen
phosphorus
potassium
chlorotic leaves
yellow leaves due to lack of nitrogen and hence amino acids
three ways of getting biologically accsessible nitrogen
industry - hraber bosch processor N2+3H2—>2NH3
biologically - symbiosis
- reuction of nitrate to ammonia
lightening
the harber bosch process uses ____ % of global energy
1-2%
_tonnes of oil is needed for every ___ tonnes of fertiliser
2
1
equation for conversion of nitrogen into ammonia
N2 + 8H+ + 8e- —-> 2NH3 + H2
what are the three problems with the conversion of N2 into biologically accsessible forms of nitrogen?
sensitive to oxygen
very large input of enrgy in form of ATP
side reactions of hydrogen that needs to be removed
how is it that legumes can be used as a cover crop ?
leguems have high concentrations of symbiotic bacteria which can convert N2 into accsessible forms of N
desccribe the formation of a root nodule
rhizobia bacteria form an infection thread - invaginate the plasma membrane
enter root hair
form a bacteroid
root cells grow around the bacteroid to form a nodule
nodule develops vascular tissue
in legumes a _____ of all carbon fixed goes to root nodules
third
in low nitrogen environments two other methods of obtaining nitrogen can occur
parasitism
carnivours - from dead animals
plants can tolerate _____ yg per meter squared for one hour but only __yg per meter squared as a yearly average
10,000
75
nitrogen is involved in the G_____ S_____ C_____
glutamate synthase cycle
- ammonia used to make glutamate and glutamine
- from here every other amino acid can be formed
what is phosphorus used for in plants?
nucleic acids, metabolties, phospholipids and ATP
describe four steps on the phosphorous cycle
agriculture puts phosphate into the soil
leaches inot sea
falls into sediment
tectonic actovoty returns in to rocks
what are two solutions to the impending phosphorus shortage?
apply more efficiently - 80-90% currently unavaliable
recycling
describe how cluster roots tackle low phosphprus
proliferation of root growth
massive increase in root surface area produces high levels of citric acid
citric acid binds to metals in the surronding soil
releases attached phosphates from metals
how do proteoid roots improve phosphate efficeincy?
no phospholipid bilayer
use galacto lipids
also lower protein production since young leaves dont photosynthesise
very few ribosomes
potassium makes up ____ of a plants dry weight
0.5 -2%
what is potassium used for?
opening stomata, transport of molecules
protein synthesis
what form does potassium come in fertilisers
KCl
why are specific transporters needed for potassium
same chemical group as Na+
Na+ is toxic in larger quantities hence cannot be allowed in as much as K+
potassium can work as a oest control e.g. ______
fungal, bacterial and viral diseases
insects and nematodes
reduces all by up to 70%
plant diseases are resposnsible for _____ of crop loss
70%
iron
chlorophyll biosynthesis
molybdenum
nitrogen absorbtion
Nickel
nitrogen metabolism
copper
chlorophyll and cell walls
zinc
enzymes and transcription
manganese
chlorophyll membranes
born
cellular functions
describe the structure of the phloem
continuous tubes of living cells
companion cells
sieve tube elements joined by sieve tube plates
mass flow hypothesis
sugars loaded through phloem parenchyma by source (passive)
flow into phloem
high concnetrration in phloem brings in water from the xylem via osmosis
mass flow occurs towards the sink organs
sugars leave the phloem where they are needed
what is the sugar transporter in arabidopsis
SUT1
what is transported in the phloem?
sugar# amion acid organic acid protein potassium mRNA no aba or nitrate - must movev in xylem
gove examples of plants that ahve C3 C4 and CAM
C3 Wheat, rice,
potatoes
C4 Maize, millet,
sugarcane
CAM Agave, vanilla,
pineapple
what is the first product of photosynthesis in CAM C4 and C3
CAM and C4 = malate
C3 = glycerate
describe the anatomy of the three types of photosynthesis
C4 - kranz anantomy
CAM - tissue succulence
compare photorespiration in C3 to that of CAM and C4
40% in C3 (up to)
undectable in CAM and C4
what is the CO2 compenstation point in C3 C4 and CAM
C3 - 40 ppm
C4 less than 5 ppm
CAM less than 5 ppm
compare growth rates of C3 C4 and CAM
C3 - 5-20 g per meter squared per day
c4 50-60 g per meter squared per day
CAM 0.5 g per meter squared per day
