deck1 Flashcards
what is the name of the oldest plant organism in the world? how old is it? where is it located
bristlecone pine, 4,700 years old, rocky mountains
discuss the modular construction of plants
the plant is made up of repeating units called modules (node, internode, lateral bud, leaf)
discuss the two different types of organs plants have
vegetative organs (used for growth);
roots with root hairs which are used for water uptake
shoots used for growth and contains xylem/phloem
reproductive organs
discuss root structure
lateral roots from primary root are used for anchorage
what are the three tissue types in a plant
dermal; outer covering of plant
ground; the tissues that sopport the plant, carry out photosynthesis or store photosynthetic product
vascular; movement of water/solutes
discuss the stages plants go through when developing a body plan
1) a zygote divides into an apical daughter cell and a basal daughter cell
2) apical daughter cell divides laterally and horizontally into an embryo
3) the 3 tissue systems form by differentiation
4) apical meristem fevelop at bast of embryo; allows for root system to develop
name the shapes a plant embryo goes through
octant, globular, heart, torpedo, seedling
name the model plant organism, name which family of plants it belongs to and why it has been selected as a model organism
Arabidopsis thaliana; cabbage family (brassicaceae) short life cycle, small genome, produces lots of seeds
state what experiment have been done on Arabidopsis thaliana to study the sequence of events in embryogenesis
mutation of genes to establish what phenotype characteristic the mutation related too
how do plants grow
1) cell elongation; uptake water into vacuole and loosen cell walls by expansin action
2) cell division from meristems
discuss location of meristems
tip of roots, shoots and leaves used for growth of shoot root and leaves
auxillary meristems at nodes used to produce lateral buds
cylinderical lateral meristems in stem/roots which allow for secondary grwoth (thickening)
discuss the root cap and quiescent centre
the root cap is an area without meristems which exists to protect the meristems when roots are penetrating through soil. it has gravity perception
the quiescent centre is of very slow cell division which produces tissues needed for the root cap to elongate
which plant hormones can be related to growth
the auxins and cytokinins cause apical dominance which leads to upward growth
the gibberelins cause elongation of internodes
what are the features of a rosette, and why is a rosette like this, what types of rosette are there
a plant that is very low to the ground with radial symmetry
internodes fail to grow
spiral phylotaxy
oppositr phyllotaxy
what does phyllotaxy mean
arrangemment of leaves arounf the stem
how can you measure plant growth and what are the equations for this
RGR=LAR x NAR
relative growth rate, leaf area ratio, net assimilation rate
what is the equation to measure leaf area ratio
LAR= SLA x LMR
specific leaf area, leaf mass ratio
whare some factors that influence plant growth and therefore explain why plants grow at ifferent rates
rate of photosynthesis
water availability
nutrient availability
genetic factors
what causes differentiation into specialised cells
internal signals like hromones as well as external signals like light induce gene expression changes
if all cells have the same genetic mateiral then how do cells differentiate into different cells
different sets of genes are expressed
discuss different plant epridermal cells and their functions
pavement cells; morphologically unspecialised cells which place out stomata and have structural function
stomata; regulate water and gas exchange
trichomes; produce chemcials and therefore offer protection against predators
root hair cells; cells with increased surface area which are specialised for nutrient uptake
what is the function of cone shaped cells on the epidermis
enhance heat and light capture
which genes and hormone regulate senescence. which cell process is key
senescence associated genes (SAG’s)
ethylene
apoptosis
what is the function of the flower has a whole
provide a mechanism of sperm and egg union
what are the two names for fertilisation in plants
outcrossing
selfing
discuss the anatomy of a flower
stamen (male reproductive organs) a filament sopports an anther which produces pollen (contians sperm)
carpel (female reproductive organs); a sticky stigma traps pollen via its hairs
an ovary exists below the stigma which produces eggs; a style connects the two structures
petals; brightly coloured to attract pollinator animals
sepals; leafy parts that wrap around flower bud and protect it during development
denine pollination
movement of pollen (containing sperm) from the anther to the stigma
what percentage of plants are flowering plants
60%
what initiates flowering
a developmental switch causes a shift from development of vegetative organs to reproductive organs;
vegetative meristems stop producing leaves and reproductive meristems start divising to produce flower parts
what can signal for flowering to begin
vernalisation (coldness), day length (photoperiod) or developmental age
what plant was used to investigate photoperiod? what were the results
a mutant tobacco (maryland mammoth) and soy beans
even if flowers are sewn over a 3 month period they all still flower within a 3 week period in september
compare short day, long night plants against long day, short night plants,against day neutral plants
short night;
hanbane
only flower if day length is above 14 hours
flower in spring/early summer
long night;
maryland mammoth
day length has to be shorter than 14 hours
flowering ococurs in late late summer/autumn
day neutral;
maize, tomato
flowering is regulated by other factors apart from dya length, such as temperature and age
whis is key in photoperiodism initiating flowering, day length or night length
night length
what percieves photoperiod, meristems of leaves
leaves, masking leaves causes flowering changes whereas masking meristems does nothing
what is the molecule that absorbs red and far red light, how does it initiate flowering
phytochtome absorbs red/far red light via its chromaphore
the molecule undergoes a confirmational shape change which impacts gene expression by interacting with transcription factors
red light and far red light exist, which causes flowering and which causes dormancy
red light causes flowering
far red light causes dormancy
these different lights reverse the effectsof eachother; the last wavelength the plant is exposed to is the one that has its effect
discuss the GNR relating to photoperiod induced flowering
1) when the correct photoperiod is present, the CONSTANS protein is stabilised
2) transcription of florigen ococurs (flowering locus T)
3) florigen enters phloem, travels to leaf and combines with flowering locus D; trnascription of APTELA1
4) APTELA1 initates flowering by commiting meristems to produce floral genes not vegatatitve genes
organ identiy genes control development of floral parts
where is florigen synthesised
phloem companion cells before being translocated
what type of gene if FLOWERING LOCUS T
What type of gene is APTELA1
FT is a flowering time genes; determines when flowering is initiated
APTELA1 is a floral identity gene
what is the ABC model of plan development
the idea that plants have 4 whorls (parts); sepals, petals, stemens, carpels and each whorl requires a different set of genes to be expressed for normal development.
how has the ABC model of the 4 whorls been investigated, what were the results
using mutants; if the a gene set is mutated then all the neccassary flower parts dont develop
which gene sets are antagonistic (prevent expression of eachother)
gene set A (APTALA1, APTALA2) and set C (AGAMOUS)
draw the table of gene sets and which whorls require them
check in notes
more complicated way of saying 24 hours and how this related to plants
circadian time cycle
leaves and flowers move in a 24 hour cycle and gene expression changes throughout the course of the day
why is plants having the ability to measure time an advanatge
it means changes in environment can be anticipated
when does a stem growth occour
night time
is the circadian rhythm effected by temperature, does the rhythm persist in the absence of external cues, can the rhythm be reset by external cues
no
yes
yes
what piece of equipment is used to measure leaf movements
a rotating drum
what happens when bean plants are placed in constant light
they operate of a 25.7 hour cycle. amplitude of movements decreases
what picks up light signal
what does this molecule reset which untilamtely causes differing gene expression
phytochrome
resets central oscillator
CCA1 (an MYB family gene) is expressed early in the day which blocks expression of TOC1 gene.
at night TOC1 gene (MYB gene) is expressed which blocks expression of the CCA1 gene
discuss concentrations of Pr and Pfr over the course of the day/night
Pfr is converted to Pr over the course of the day, when is converted back to Pfr overnight
what are the two carbodydrate molecule in plants and where are they synthesised
starch; synthesised in chloroplast
sucrose; synthesises in cytosol
do most plants store starch or sucrose in the roots, what an example of a plant that doesnt
most store starch
beet stores sucrose
what molecule are carbodydrates moved as and why
starch; it is used for transport because its a stable non reducing sugar
what is evidence for the phloem being used to transport of assimilates
dridling (ring barking) blocks translocation
radioactive marked sucrose has been shown to be moed into the phloe
what species of plant has mainly amino acids in its phloem, compared to most plants (mainly sucrose in the phloen)
cubitacaea
discuss the anatomy of the phloem system
sieve tubes; nuclues lacking, organelle lacking tubes
sieve plates exist between sieve tube cells, they have holes in them to allow passage of assimilates
companion cells; interacts with sieve tube element and has a role with loading/unlaoding of assimilates
what is the bundle sheath
a layer of cells sorrounding the vascular bundle
what is the pressure flow model
a model which explains transport of assimilatesin the phloem;
when assimilates are loaded into the sieve tube, the water potential to decrease, so water moves by osmosis from xylem into this part of the phloem; hydrostatic increases and forces sap through sieve plates towords sink.
at sink the assimilates are unloaded, which increases water potantiol so water moves back into the xylem
is there a low or high energy requirement for translocation
low
what are the two methods of laoding assimilates into the phloem
symplastic; through plasmodesmata. requires a high concentration gradient
apoplastic; assimialtes are moved across cell membranes into apoplast. this requires energy
what is the polymer trapping model
the idea that the cells between the vascular bundle and the bundle sheath convert sucrose into raffinose (trisaccaride) and stachyose (tetrasaccaride) before the molecules enter the sieve tube
what are the 3 routes of unloading from the phloem; which plants use each method
symplatic; sucrose moves into cells via plasmodesmata;
leaves/root tips
apoplastic; sucrose is unloaded into apoplast before active transport into cells
sugar cane
apoplast; sucrose is unloaded into the apoplast before being hydrolysed into glucose and fructose which is then actively transported into cell
legumes
how is it determined which sink the assimilates go to
sink strength (sink size x sink activity) proximity of sink to source is important as well as the vascular connections to different sinks
discuss stomata physiology
2 guard cells exist which have thickened inner walls.
stomatal pore between guard cells
guard cells are sorrounded by subsiduary cells
discuss the three different ways stomata can be arranged
randomly
clustered
in linear rows
whats the equation for stomatal density
number of stomata/leaf area
what is the stomatal index
the number of stomata in relation to the number of epidermal cells
which gene controls stomatal pattrerning
ERECTA (ER)
discuss how monocot and dicot ( 2 types) differ in where stomata are located
monocot; 50% lower
woody dicot; 100% lower
non woody dicot; 60% lower
what is the name for a non woody dicot
herbaceous
discuss the mechanism by which stomata open
1) H+ expelled from guard cells and create an electrochemical gradient (ATPas activity)
2) K+, Cl- and H+ enter guard cells from subsiduary cells, and are transported to the vacuole reducing water potentiol
3) water enters which causes cells to swell
what is the mechanism by which stomata close
1) Ca+ enters guard cells
2) K+ and Cl- channels open causing these molecules to leave guard cell down thier concentration gradient
3) what potentiol in vacuole increases so water leaves
Ca+ also inhibits the action of the H+ ATPase
whats an osmoticum
a molecule that helps maintain osmotic pressure
when K+, H+ and Cl- enter vacuole, how is the postive charge balanced
starch is broken fown into malate which is negatively charged
what are protoplasts and how have they been used to investigate this mechanism
free cells that havehad their cell wall degraded.
they have been used for patch clamping (using an electrode to measure ion movement
name an inhibitor and an activator drugs of the H+ ATPase
fusicoccin stimualtes the enzyme
CCP and vanadate inhibt the enzyme
how is the H+ATPase activated (and therefore stomatal opening activated)
xanophylls percieve blue light and activate the enzyme
why do CAM plants not open their stomata during the day
their xanophylls respond differently to blue light and dont initate H+ ATPase activity
discuss how co2 concentration and water vapour loss relate to stomata
when the carbon dioide concentration in a plant is high, the stomata are closed as no co2 uptake is required
loss of water vapour causes stomatal closure
discuss the 2 different types of stomatal closure in relation to loss of water vapour
hydropassive; water loss causes stomatal cell shrinkage; direct closure
hydroactive; loss of water vapour causing a signalling process to occour leading to Ca+ influx which causes stomatal closure
what is the mechanism by which ABA causes stomatal closure
ABA is transported from the roots to the leaves where it causes causes the calcium channels to open and calcium to enter and causea cascade of effects leading to stomatal closure
discuss the boundry layer and wind speed in relation to water loss
the boudry layer is the layer of air around the leaves. if wind speed is high then water vapour is moved out of the boundry layer and water loss occours more
what is the water use efficiency and which plant type has the highest value
molecules of co2 taken in for every water molecule lost
CAM plants, then C4 plants then C3 plants
what is the mid day depression
when c3 and c4 plants close their stomata at midday for a short period of time to avoid water loss at the hottest time of day
discuss the advantages of CAM plants opening the stomata at night in terms of stomatal resistance
the stomata can be closed during the day therefore plants have high stomatal resistance to water loss
what % of crops loss does abiotic stress cause
40%
what are the 4 different types of responses plants have to stresses
localised; occour in a specific part of the organism
symstematic; occour throughout the whole organism
short term; ococur within minutes
long term; takes days/weeks to occour
plants can either _______ or ______ to plant stresses
resist; change physiology and metabolism to avoid the effect of the stress
avoid; perceive stress and dotn respond. the metabolic cost of responding isint worth it
why does water loss effect plants
1) water loss means increase in concentration of solutes, which may alter pH etc and effect enzymes
2) plants have to close their stomata to stop water loss; reduced carbon dioxide uptake means reduced photosynthesis and therefore growth
3) ageing is accelerated
4) rehydration makes membranes porous
discuss the 3 biochemical responses to water loss
1) production of compatible solutes which increase osmotic force and drive water into cells
2) produce hydrophillic proteins like LEA which retain water and release it slowly
3) induction of CAM; metabolism
discuss anatomical responses to water loss
1) formation of an enhanced root system that penetrates deeper soils
2) ensure that when new leaves are formed they have a lower stomatal density and more wax to icnrease stomatal resistance
3) existing leaves are stopped from expanding, and have their stomata shut
4) become succulent; produce water storage tissues
state 4 ways that plants that live in water scarce environments are adapted to lack of water
1) extended root systems
2) reduce metabolism
3) short life cycle; germination, flowering and setting seeds all occours in short wet season
4) oppertune leaf production; only producign leaves when water is available
discuss water excess as a stressor
state 3 adaptions to this environment
roots submerged in water is a problem because it means no oxygen or nutrient uptake
1) production of alcohol fermention enzyme (ATP can be produced without oxygen)
2) production of pneumatophores; root like extensions in air for oxygen uptake
3) aerenchyma has evolved; parenchymic cells (ground tissue) form air vessels to transport oxygen from shoots to roots
where are aerenchyma located
they surround the vascular system
what is salt stress most commonly caused by
high cocnentrations of ions (Na2+ and Ca2+ in particular)
discuss locations where salt stress happens
lakes where evaporation exceeds precipitation
irrigated soils
groundwtater when the area recieves little precipitation
coastal marshes (wetlands)
discuss the two ways salt stress changes soil, which then has negative impacts on plants
water cant move freely in salt stressed soil (its been made more porous/aerated which means less hydraulic action)
salt stressed soil has a lower water potentiol than normal soil; less uptake of water occours
what effects does salt stressed soils/water have on plants
ionic imbalances between different cell compartments
enzyme inhibition occours leading to cell death
reduced photosynthesis and therefore reduced grwoth
discuss the three plant types in relation to salt environments and an example of each
glycophytes;
get salt stressed at high salt concentrations
can survive in soil with max 100mM NaCl
most plants; rice
salt tolerant non-halophytes;
plants that can tolerate salt concentrations of up to 200 mM NaCl
tomato
halophytes;
plants that are adapted to salt concentrations of 500mM NaCL and show increased growth at these conditions
ice plant, salt cress
what are some mechanisms plants use to reduce salt stress
produce compatible solutes to drive water into cells so ions are less concentrated
high selectivity of ion uptake
presence of ion transporters in cells allows for ions to be sequestered into vacuoles where they cant effect metabolism
rootss extrude toxic ions that have been taken up
name some compatible solutes
discuss which charge is possessed by compatible solutes
amino acids like prolin, betaine
neutral charge
discuss how some plants are adapted to salt stress
high quantities of compatible solutes
presence of bladder cells; cells with large vacuoles that can sequestrate high large quantities of salt
presence of glands that can exrete salt to the surface
what is a plant type that can extrude salt to the surface
mangroves
what is usually the optimum temperature for plant growth
20-30 degrees centigrade
discuss the effects high temperatures have on plants,
responses plants can have to high temperatures
discuss adaptions plants have to high temperatures
effects include
1) increased evapotranspiration which causes plant wilting
2) reduced photosynthesis due to enzyme inhibition/denaturing
3) increased respiration and therefore photorespiration
4) increased fluidity of the thylakoid membrane
responses include;
1) stomatal closure to reduce water loss
2) increased expressionof heat shock proteins (HSP’s) which stabilise enzymes in high heat
3) increased synthesis of saturated fatty acids for the phosopholipid bilayer to reduce fluidity
adaptions to high heat conditions are possessed by thermophiles;
1) rolling of leaves which reduces transpirational losses of water
2) thin leaves which are best for losing heat
3) presence of a thick waxy cuticle which reflects light
what temperatures can agave and cactus survive in
70 degrees centigrade
discuss effects that low temperature has on plants, responses plants can have and adaptions plants have
effects can include;
1) reduced enzyme activity which leads to reduced metbaolism
2) decreased membrane fluidiy due to crystalisation
3) reduced water availability as water turns to ie
4) reduced photosynthesis
responses to low rtemperature conditions incolve;
1) increases synthesis of unsaturated fatty acids for the phospholipid bilayer to increases fluidity
2) increased synthesis of compatible solutes which prevent water from freezing
3) increased ion uptake from soils which decreases the freezing point
adaptions to low temperature conditions involve;
1) accumualtion of LEA proteins to retain water
2) induction of dormancy
3) starch breakdown into soluble sugars
what is a plant that can survive in temperatures as low as -70 degrees
laryx dahurica
name some pollutants in the air
sulphur oxides carbon oxides nitrogen oxides peroacetyl nitrate (PAN) heavy metals
discuss effects on plants that air pollution has and responses
air pollution causes plants to close their stomata, habe lesions (damaged tissue), necrosis (cell death), bleaching (loss of chlorophyll)
responses to air pollution stress include closure of stomata, production of enzymes like peroxidases which detoxify cells
and production of ROS-scavenging compounds
what is a mechanism by which air pollutants cause damage within plants
air pollutants produce Reactive Oxygen specues (ROS) which cause a cascade of reactions within cells and damage membranes etc
what is one example of an ROS-scavenging compound
absorbic acid
glutathionine
heavy metals can pollute soils, name some heavy metals
lead, nickel, cyanide, mercuary
what are two characterisitcs of plants that thrive in heavy metal polluted soil
those that can selectively uptake nutrients and leave behind heavy metal elements and those who can sequestrate heavy metals
name some plant methods of sequestration
combining metal ions with amino acids containing sulphur
combining heavy metals with acids like malate
production of phytochelatins which are sulphur containing polypeptides which bind to metal and move into the vacuole where the heavy metals cant be damaging
deifne phytoremediation
growing specific plants of heavy metal polluted soils that will upake and sequestrate the heavy metal ions
define phytomining
growing plants that hyperaccumulate heavy metals, and then harvesting the metals from the plants
discuss the 4 receptors that exist
1) cytoplasmic receptors (CR) which ligands bind to after diffusing across plasma membrane. binding causes a conformational change in receptor causing a chaperone to disccoiate allowing the receptor to move into the nucleus
2) ion channel receptors that that open due to chemical signals and physical signals
3) G protein coupled reactions (GPCR); a ligand binds to the ectracellular N terminal causing the C terminal in the cytoplasm to cause a signalling cascade via secondary messengers like cAMP.
4) receptor like kinases (RLK) a ligand binds to the extracellular N terminal which causes a conformational shape change of the transmembrane domain causing a protein kinase at the C terminal to be activated which causes a cascade fo effects via phosphorylation
which receptor is common in animals and why is common in plant cells
animal cells tend to have G protein coupled receptors where as plants have Receptor like kinases
where is calcium concentration high
extracellularly,
within compartments in the cell like the ER, vacuole
NOT in the cytoplasm
what type of moelcule is cAMP and how is it is produced
cAMP is a cyclic nucleotide. G proteins activate Adenylate cyclase to convert ATP to cAMP
name two groups of proteins cAMP activates
ion channels
protein kinases
discuss NO as a secondary messenger
NO synthase is activated by calcium and convertes arginine to NO, which goes on to cactivate enzymes that convert GTP to cGMP
discuss the phosphoinositide pathway
A G protein receptor is activated, so that one of its subunits dissociates and activates the phospholipase C enzyme which releases IP3
discuss differences betwen plant animal hormones
plant hormones are sometimes called plant growth regilators
plant hormones are produced at specifiec sites and may act systematically rather than at specific areas
are hormones present at high or low concentrations
high
discuss the effects auxins have
apicial dominance; the auxins are only transported to the apical bud
cell elongation by activating protein pumps that move protons into the cell wall and decrease pH which activates expansins to loosen cell wall
degrade TF's which cause nutrients to be moved from old leaves to new leaves cause gravotropism (downward root growth)
how are auxins synthesised
the trypophan aminoacid is transaminated into IPA, which is decarboxylated into IAALD, which is oxiadted into IAA
discuss how auxins mov ein plants
only only move in polar way (downwards). they are transported out of cells via efflux transporters called PIN proteins
discuss applications of auxins
when used in high concentrations they have a herbicide effect
at low concentrations they have anti-senescence effect and can be used to stop fruit drop
where are high concentrations of auxins found
meristem regions of growing organs
discuss the forms of auxin
it exists in a free form and a conjugate form (attahced to a guar or protein). this storage conjugate form can be hydrolysed to release active auxin
how are auxins degraded
oxidation by peroxides
UV light
performing oxidative decarboxylation of IAA
whjat effect do gibberelins have
cause stem elongation through cell division
stimualte flowering in response to long days
break seed dormancy
stop senescence
how are auxins synthesised
acetyl CoA is converted to gibberelins via the mevalonic acid pathway.
most are inactivated upon synthesis, and are then reactivated when they have been transported to where they need to be
how many carbons do gibberelin molecules have
19/20
how are gibberelins transported
in both xylem and phloem
can be transported in both directions unlike auxins
discuss applications of gibberelins
produce seedless fruit which are much larger than they normally would be
increase crop yields due to elongated internodes
make plants bolt (grow quickly and set seeds)
what is the effect of cytokinins
work alongside auxins during morphogenesis of tissues
cell elongation
delayed senescence
discuss the effects abscisic acid has on plants
induces seed dormancy
induces stomata closure
promotes abcission and senescence
discuss the applications of abscisic acid
it can be applied to plants to prevent transpiration/water loss
discuss the effects ethylene has
induces fruit maturating and ripening
causes senescence
how is ethylene transported
in the air from plant to plant, and then in the xylem and phloem when its inside plants
how is ethylene synthesised
all organs are capable of producing it. the methionine amino acid is used as a substrate
discuss ethylene applications
can be used to induce ripening
discuss the effects of jasmonic acid
used for communication within a plant and between plants
defence against predators; activation of inhibitors which poison animals
how is jasmonate synthesised
whena leaf is damaged the phospholipid membrane breaks down into molecules that are converted to jasmonates, which enter nucleus and change transcription
discuss the long distance signalling pathway involving ABA
roots detect water stress and produce Abscisic acid which travels in the xylem to leaves and induces stomata closure
discuss the long distance pathway involving auxins
auxins are produced at the top of the plant and then transported via the stele (central root) where it has gravotropism effects
discuss long distance signalling of nitrogen content
plant shoot measures nitrogen content and signals for changes in amount of nitrogen transporters in the roots via altered expression
discuss long distance signalling for hypoxic soils
when the roots are flooded, ethylene is used to signal this condition and oxygen is transported via aerenchyma to the roots
how is oxygen concentration detected
indirectly through changes in pH, ATP concentration. low oxygen concentration activates ethanol fermention, which doesnt require oxygen
which partof the plant signals the carbon dioxide concentrations
mature leaves
how does the plant respond to increased atmospheric co2 concentrations
new leaves have lower stomatal density
in terms of plant to plant communication, what do jasmonic acid and ethylene signal for
ethylene signals pathogenic attacks and environmental stresses
jasmonic acid signals for wouldings, for example from grazers
what chemical to plants release into the soil in order to be competitive
sequiteropenoids are released into the soil and inhibit germination of other plants
what is a hydroponic culture
a water environment with nutrient concentrations defined
another name for a nutreint solution
hoglands solution
what are the macronutrients
nitrogen, potassium, calcium, phosphorus, sulphur, magnesium, silicon
what are the micronutrients
calcium, magnesium, zinc, copper, iron, nickle
what are three main elements in plants
carbon 45%
oxygen 45%
hydrogen 6%
what charge do soil particles have and what charge do nutrients have
soil particles are negatively charged
nutrients are positively charged
what is a colloid’s
an insoluble substance dispersed/suspended through another substance. mineral nutrients form micelles
what effects weather or nor mineral nutrients are taken up from soil
the pH of the soil effects weather or not nutrients are uptaken. all nutrients have an optimum pH for uptake (slightly acidic)
what are depletion zones and how to plant respond to them
zones of low nutrient concentration that form near to the roots. the roots detect this zone and grow towords areas of high nutrient concentration
define rhizosphere
the beneficial interaction between plant roots and microbes to maximise nutrient and water uptake
what are the differences between mutalism and symbiois
mutualism benefits both partners whereas symbiois benefits 1/both partners
what is the name of the association between plant roots and fungi, discuss this associaiton
mycorrhizae; fungi obtains carbohydrates and plant recieves minerals. the fungis hyphae grow around the root and are known as a fungal sheath. mycelium extends into roots and either penetrates cells or forms a network between cells
what is the collective name for a fungi’s hyphae
mycelium
what nutrients does the plant gain from the mycorrhae interaction
nitrrogen, potassium and phosphorus. mainly phosphorus
what percentage of plants have mycorrhizae interactions
80%
when are mycorrhizae interactions missing
in dry, flooded, nutrient poor or saline soils
discuss the difference betwen ectomycorrhizae, endomycorrhizae and ectendomycorrhizae
ectomycorrhizae; an external sheath of mycelium exists perhaps with hyphae between cells but not penetration into cells
endomycorrhizae; there is no external sheath of mycelium but there is a well developed hartig net and much penetration of cells
ectendomycorrhizar; a well developed hartig net is present with possible penetration of cells and minimal hartig net
define hartig net
the hyphae network between plant root cells
what is the name of the bacteria plants form an association with
rhizobium
which plant group forms the rhizobium interaction
legumes
how do plant cells become infected with rhizobium bacteira
the plant releases flavanoid compounds into the soil which is detected by bacteria which produce nodulation factors; this causes root hair cells to grow in a curled wat around the bacteira
how do rhizobium fix atmospheric nitrogen
they have the ferredoxin-nitrogenase complex (N2>NH3). ammonia is toxic so plant processes it into glutamate
name a third plant-microbe interaction
fern-blue-green cyanobacteria
cyanobacteria enter growing shoots and fix nitrogen in specialised cells called heterocysts
south asian rice fields
discuss similarites between plants and algae
both have a cellulose cell wall, similar enzymes, same type of rRNA, use of chlorophyll a and b for photosynthesis and form a cell plate during cell division
what is the name of molecules needed by land plants for protection against UV light
carotenoids
how many plant species exist
450,000
how many species of angiosperm are ther
260,000
