biol235z Flashcards
introduction to biol235z
organisation
workshops:
-discussion on defence
-practice for data interp
-practical prep
-review writing skills
-practice for data inter
reading material:
introduction to plant ecophysiology
physiology:
the branch of biology that deals with the functions and activities of biological organisms and their parts
ecophyiology:
how plants work when they interact with their environment (plant behaviour, mostly through growth)
list environmental factors that you think can have an effect on plant physiology?
-pathogens
-temperature
-wind
-nutrients
-ph
interactions
biotic: interaction with another living organism
abiotic: any type of environmental interaction
in terms of evolution of plant defences, what is the essential difference between biotic and abiotic damage?
abiotic factors have been around for a long time, but you get co-evolution with biotic factors. So the defence will no longer be efficent (arms race)
is shade a biotic or abiotic interaction of the environment?
mostly biotic but a bit of both
stress
adverse force or influence that tends to inhibit normal systems from functioning optimally
any external constraints that limits fitness below the genetic potential of the plant
main stresses responsible for losses
weather
not enough nutrients
how can genetic potential of a plant be measured?
its difficult
optimimal of output?
what is considered as a measurement of genetic potential?
see when the output is the best, optimimal conditions this could be crop yield etc
what info is missing from the figure legend?
time (year of record)
space (where did this occur)
2 types of stress
lack of an essential element
adverse force
factors that results in physical or chemical damage
what is essential to plants?
-water
-light
-soil
-carbon dioxide
-oxygen
at what temperature does heat become stressful?
what are the potential strains for drought? heat? pathogen attack
things are only if a stress if it creates a strain
stress:
strain:
stratergies to survive and thrive in a stressful enviornment
seed coat, spore
make sure not around when the stress occues
escape the stress: make sure not around when the stress occurs
prevent the stress from generating a strain: avoidance
stress tolerance: repair/ minimise the damages caused by the strain
adaptation to stress: heritable mods in structure or function that increase fitness
acclimation to stress
what does plant do during hardening treatment?
accumation
Do know any adaptations of photosynthesis to temperature?
c4 and cam metabolism
how is stress resistance studied?
morphological level: look at the same of the plant
cellular level: look inside the plant see whats happening in terms of metabolism
molecular level: gene expression, rna etc
phenology: periodic events, when things happen
lecture 2: chemical defence
eco-phyiological reponses plants have to the enviornment
plants face challanges from herbivores just as much as everything else
therefore resources needed, different allocations at different times.
*understand how/why plants defend against herbivore attack
*understand how allocation to defence impacts
chemical defence or not?
the chemical arsenal
plant defence
definition: any morphological, biochemical or structural characteristics that reduces the likelihood of herbivory or its sunsequent impact on plant fitness.
*stinging trichomes, biological (ant and acacia), latex/sap, physical
pre-eminence of chemical defence
most papers on chemical defence, very easy to quantify
plant metabolites
(carbohydrates, proteins, lipids) contribute to photosynthesis, respiration, assimilation, cell division
secondary metabolites:
plants have loads of organic compounds with no obvious function. Tend to be found in restricted taxanomic groups.
plant secondary metabolites?
what are they for?
-uv protection
-allelopathy
-nutrient cycling
mutally exclusive?
these metabolites may solve more then one purpose
edwards (1989) natural defence
came up with neutral defence could have evolved along time ago but now has another benefit.
could have been expressed for one thing but now protects against herbivory.
if you can demonstrate a protective role for the plant then the secondary defence acts as a anti herbivore protection.
defence or not?
PSMs are not linked to growth or development and are taxonomically restricted, but its a chemical defence if protective.
some of the chemicals involved and what they do
1980’s the big three
*nitrogen-containing
*phenolic compounds
*terpenes (carbon based)
terpenes
largest class of PSM
synthesised from acetyl-CoA
produced in an isopreme unit, lego block of terpene, this joins together creating (2)monoterpenes, sesquiterdepine(3), diterpene(4)
examples: pyrethriods (cyrysanthemum)
used in head lice killer
monoterpenes (pine smell toilet cleaner)
mant terpenoids are smelly
pine terpenes through the ages
iason et al (2011)
how different terpines effect different herbs at different species times
*trees are attacked by different herbivores throughout their life-history.
volitile protein changes, through the life cycle detering different herbviores at different stages of growth
south african grasshopper
eating a toxic plant and using the chemicals to generate a defence itself (colour)
consumes milkweed
has a way of breaking up the alkaloids and then as a defence it pushes the alkaloid out of its back through thoracic glands (toxic foam)
phenolics
10k different compounds
aromatic ring
in higher plants synthesised mainly via the shikimic acid
lignin-provides mechanical support but also reduces digestibility (its why plants are cruddy) strutural
tannins- are both feeding deterrents and have toxic impacts on growth and survival
make up tea, apples, wine (shark taste)
phenolics down under
a general pattern emerges for proteaceae seedlings attacked by vertebrates
planted seedlings out in the field and looked at rates of attacked out in the field and the amount of phenolics produced
the more phenolics produced the less likely to get eaten
negative assocation between phenolic
nitrogen-compounds
synthesised from amino acids
chemically and found in about 20% of vascualr plants
(allocation choices)
alkaloids are characterised by the hetercyclic ring
a variety of human use (fabacce)
alkaloids in action
hanley et al
started at the seedling stage
sowed in 6 different see species
allowed slugs and snails to feed freely
other not
only grazed at seedling stage
results
the stuff that was grazed is dominated by ragwort and grasses
highly grazed were weedy, but outcompeted in the weedy section even tho slugs wouldnt eat
ragwort putting all effort into chemical defences and not on growth therefore out competed by the weeds (dandelions)
cyaogenic glycosides
(cyanide)
common in fabaseae and rosaeae (almonds)
holding cyanoid in the tissues inly released when eaten
probelm: its a respiratory poision and plants also do respiratory therefore they keep an enxyme and glycosentate only mix if the plant is destoryed
*describe futher
lythic enzymes also catalyse this process (spit)
other bits are defended by herbivores
flowers
hakeas- take a lot of effort to create
produce big red obvious flowers because they are bird pollinated and need to be visible.
this accessabilty makes them a target too, therefore they are laced full with cyanoid . Pollinating birds dont effect the membranes just pollinate
glucosilinates
what makes cabbages smell of cabbages
similar principle to cyanoid in hakeas
decompostion of aglycone releases sulphate
(catalyised by spit of the herbivore)
GLS and enzymes again are stored separately
the white response to GLS (cabbage white butterfly)
gravid females use the highly volatile isothicynate smell to locate plants (renwick 1992) can detoxify the chemicals and thus get the food resource for themselves and other predators wont come near them due to the alcayanoids
larvae rediret the GLS hydrolysis reaction
an evolutionary arms race?
despite an array of diverse chemical weapons, call plants get eaten
1960’s- evol arm race
plant responds, then herb responds etc back and forth
*milk weed
*south african catapillar
shows the tropical diversity in tropical regions
Explain neutral defence:
was used or something but now is used for another role.
An adaptation for one ecophysiologcal factor co-opted for anti-herbivore defence/deterent
what moelcules are shown:
phenolic ring
terpin
lecture 2: structural defence
last time chemical defence
LO: defence or not?
the structural arsenal:
interactions
structural defence- the poor relation
all the basics that apply to chemical is logical to structural.
examples:
spines, hiars, tough leaves and minerals- what are they for?
structural support, reduce water loss, thermal protection, uv protection
strauss and agrawal (1999)
a trait can be viewed as a defence even though defence is not its primary function
how do we mean by structural defense?
Any morpholical or anatomical trait that confers a fitness advantgae to the plant by directly deterring herbivores from feeding on it
(hanley at al 2007)
spinescence
spines: sharp-pointed, petioles, midribs, veins or stipules (holly-highly rolled lumps of lignin. Leaf mod)
Thorns: sharp-pointed, woody branches. Prevent herbivores by climbing. Can be seen in seba
spines- better against big herbivores
how do we know this: evidence of this
give herbivores plants with or without spines, given to kangeroos in captivity.
(hanley et al 2007)
hakea species
give same plant without the spikes and the twig without spines were more eaten.
other studies:
thorns on acacia in kenya
removal of thorns from african acacia= 74% of branches then eaten. Reduce in recovery for the non-defenced plant.
a way of proving this:
see whether simylated herbivore attack equals more thorns.
increase graph grazing increase in thorns in this area
pubescence
hairiness in plants
(tricombs)
layer sof trichomes on leaves, stems and flowers.
example of species:
stinging nettles
trichome types: morphology
spiral, straight, stellate, hooked.
can also produce a chemical
more subtle in how it works:
-reduces tissue ingestation
-reduce obiposition (butterflies can get ovipositor into a nice spot)
-reduce movement/trap insects
most effective on small invertebrate herbivores
evidence the defensive role:
induced pubesence by herbivore attack
Traw and dawson (2003)
using black mustard
leaf hairs were more dense, induction of more and bigger leaf hairs
sclerophylly
(hard leaved)
hardness due to high lignin and cellulose content (former is hard to digest)
if a plant builds enough of these it creates a strucural barrier to attack
somewhat distasteful
example: dwarf palm/holly
makes the point that the idea of sclerophylly. common in mediterranean-climate regions
why is sclerophylly common in mediterranean-climate regions?
-prevent water loss
-protection cells against high UV
-layer of hazy chemical above the leaf takes some of the UV
-when the herbivores are around it prevents herbivore consumption
(defence against herv attack)
-more large herbivores
-protect against uv
-prevent water loss
sweets of co-adaptive traits
no way of knowing which is the most important
minerals
silicon-based plants absorb monosilicic acid (si(OH)4) from soil
a sweet of chemicals plants above and below ground
transported to the shoot epidermis to form biogenic silica
this forms opaline phytoliths
phytolithos are the most common in poaceae
(cuts when pulling on grass)
increased leaf abrasiveness means more tooth/mouthpart wear;reduced digestibility
-good defence against mammal and invertebrate herbivores
*feed grass hoppers with this it even wears down their mouth parts
grasses and voles
massey & hartley (2009)
varied the silica content soils if its offered
where more silica is taken up the abrasiveness of the grasses increased thus the attack by herbivores such as voles declined.
same paper also shows more silica defence once herb attack is experiecned
calcium minerals
(calcium oxilate)
not just above ground parts that are defended but also below ground parts
defending bulb attack even below ground
many inter-tidal algae secrete calcium carbonate
fell gritty ehrn you touch them, coraline algae. Reduces intertidal gastropods attack.
Structural defences vs chemical defences
constraints
both chemical and strucutral defences require carbon and/or nitrogen.
herbivores aren the only thing a plant needs to worry about. Carbon coming from photosynthesis and nitrogen from the ground.
both limited
plants grow and reproduce
saying it with flowers
many hakeas have conspicious, accessible inflorences for bird pollination
takes a lot of effort in a resource limiting environment
producing these flueorsnces leaves you vunerable for unwanted attention from emus etc
therefore they produce lots of cyanide to prevent attack
25-30% produce these big atttractive flowers
most make generally white/ light pink clour but these have rolled spinence of leaves
spines protecting from attack but what polliantes them?
insects acts as pollinator
2 ways of being a hakea
bird pollinated:
big without spines, but low level of physical defence but high chemical defence
insect pollinated:
inaccessible infloresnces
not as much chemical defences
thus trade offs between pollination
defence linked to other selection pressures?
which came first the bird pollination because of the naturally high levels of cyanide or did this adaptive to this.
seems as a paralell
hanley et al 2009
what about fruit defence?
if hakea infloresences are defended by spines what about fruits?
more devleoped on insect pollinated species
bird pollinated fruits tend to be bigger and tougher then insect pollinated.
have to be tough as a fruit due to parrot herbovires that want the seeds within the capsules.
so defence seems to be water tight
but cockatoos think differently
regenerate after fire
but a herbivore will overcome a defence sooner or later- arms race
however water tight a defence something will overcome it
selection pressures:
however clever the plant is for allocation of choices less resource then to growth and reproduction, anti pathogen defence, cold.
pracitical: induced defences and volatiles
plant defence seminar
pre notes
out of the quagmire of plant defence hypotheses:
hypotheses: optimal defence (OD), carbon:nutrient balance, growth rate (GR) and growth- differentation (GDB). All serving as frameworks for investigating the patterns of plant defense against herbivores.
OD- served as a main framework for investigation of genotypic contribution of CNB hypothesis expression of plant defence.
GR- explains intrinsic growth rate of plants shaped evolutionary by resource avaliabilty affects defensive patterns
GDB- recognises the constant phyisological tradeoffs between growth and differentation at the cellular and tissue levels relative to the selective pressures of resource avalibility.
cost and benefits
wiki article
The final consideration is cost: how much will a particular defensive strategy cost a plant in energy and materials?
This is particularly important, as energy spent on defense cannot be used for other functions, such as reproduction and growth. The optimal defense hypothesis predicts that plants will allocate more energy towards defense when the benefits of protection outweigh the costs, specifically in situations where there is high herbivore pressure
the evolution and ecology of plant tolerance to herbivory
The tolerance of plants to herbivory reflects the degree to which a plant can regrow and reproduce after damage from herbivores.
How sessile plants defend themselves against attack from herbivores:
olerance, the ability of plants to regrow and/or reproduce after herbivory, could serve as such a defense. This ability has been investigated by agriculturists, who were stimulated by the need to estimate the economic costs of herbivory; however, plant tolerance to her- bivory in natural populations has only recently received attention.
*terrestrial plants in natural communities sustain 18% damage in the field
*The degree of tolerance to herbivory is not necessarily directly related to plant fitness. For example, a plant that compensates completely for herbivore damage could still have lower overall fitness than less tolerant genotypes with high fitness in both damaged and undamaged states (compare genotype F versus C, D and E in Fig. 1).
Definitions of terms related to plant tolerance and defense against herbivory
Defense: any trait that confers a fitness benefit to the plant in the presence of herbivores. A trait can be viewed as defensive even though defense is not its primary function. For example, the primary role of flavonoids, known deterrents of herbivores, might be to protect leaf tissues from UV damage.
Resistance: any plant trait that reduces the preference or performance of herbivores43.
Tolerance: the degree to which plant fitness is affected by herbivore damage relative to fitness in the undamaged state. Tolerance can be estimated only from a group of related or cloned plants because the fitness of an individual plant cannot be examined in both damaged and undamaged states.
Compensation: a term used to refer to the degree of tolerance exhibited by plants. If related damaged and undamaged plants have the same fitness, then that family has the ability to compensate fully for herbivory. If damaged plants have greater fitness than their undamaged relatives, then plants have overcompensated and if they have lower fitness, they have undercompensated for herbivory.
intrinsic factors (age, size etc)
feedback loops:
For example, removal of leaf tissue by herbivores decreases leaf area available for photosynthesis, but can also increase light levels to previously shaded portions of the canopy, thereby increasing photosynthetic capacity in remaining leaves
plant defence theory:
*allocation of resources
*how the idea has matured into theory
what are the 3 principle trade offs here?
*bird pollinated:
- colourful, no/less physical defence, influorecences: accessiblity (need to be highly accessible for birds to be able to access): chemical defences
*insect pollinated
-less colourful, more physical defence.
inaccessible inflorescences
defence theory
4 main hypothesis:
which one captivates the best?
*GR:
optimal defence theory:
(exam content)
what are the three elements of ODH?
*risk of attack (apparancy) how obvious to the herbivore
*cost of plant defence
*value of plant part having to be defended
which of a mediterranean shrub or arable annual is more apparent?
poppy- doesnt live long so get through life history.
shrub: is there for longer so it has more of a risk longer
think of an example where apparent high-value plant parts are well defended?
*wild parnsips: flowers
*hacea (big red flowers)
ODH issues
*apparaency is difficult to quantify (what animals will be more attracted then others)
no consistent evidence for link between apparency and defence allocation in literature. Thus cant quantify.
only worth incurring defence costs when herbivores present, else theres a fitness cost.
growth rate hypothesis
defence is determind by plant growth rate- in turn determind by available resources
GRH predicts that allocation to defence increases as growth potential decreases
get reproduction bit down then allocate resources against defence.
thus plants in resource-poor areas with inherently slow-growth rates as theres not alot of resource there (water, soil nutrients) thus cant turn over roots/shoots very quickly.
GRH prediction
how does light limitation affect allocation to induced defence?
competitive shade-intolerant fast growth plant species then rates of induction exihibit higher induction then slow-growing (shade tolerant) species
according to GRH which of a med shrub or arable annual is best defended?
med shrub: slow growth effort, makes sense to allocate defence structures
carbon: nutrient balance
allocation determind by the carbon: nitrogen ratio
plant growth in nitrogen-deficient soils more limited that p/s-plants. plants allocate excess c to carbon based defences
*resource avalibility
plant isnt wasteful, where not light limited then excess carbon is moved somewhere (lignify structure)
*maybe this is why alkanid limited: drugs, tobacco
what happens to the carbon-nutrient interaction if we increase atmospheric co2 concentrations? (nitrogen lacking)
*decrease relative balance in the plant
*excess carbon turned into plant structural defence.
more cruddy in eco2 as lignocellulose allocation increases (herbivore preferences change)
growth- differentation balance
what is the dilemnna at the heart of GDBH?
the trade off grow or defend
*resource acquisition
but in doing so they’re taking away from defence.
compete vs herbivory defence
(grow quickly and acquire quickly) more competive ability
*phyisological trade- off between growth
what is the cellular basis of this theory?
need to be bigger
differentiation- trade of inherent
growth-cell division and enlargement
resources and the GDBH
where resources limit phosynthesis, carbon supply limits growth and defence.
as resources increase photosynthesis requirments are met allowing CHO. But not enough to support growth, so C compounds used synthesise carbon based defence (phenolics, tanins)
optimal defence
GDBH is most mature hypothesis
but what about tolerance
many plants can simply re-grow (compensate) following tissue loss- how does this fit into plant defence theory?
*plants have the ability to tolerate in this framework.
how plants quickly reallocate resources
agrawal and fishbeins (2006)
triangle of plant defence
tolerance/escape
low nutritional quality
nutrition and defense
what have we learned?
