Bio 3475 Lec 2.docx

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26 Apr 2012
Bio 3475 Lec 2 9/24/2010 10:32:00 AM
Resource acquisition
Chapter 2 Resource Acquisition
Plants and animals use infochemicals to acquire resouces
Classification of nematophagous fungi
a. Sp which catch nematodes with either mechanical or sticky traps;
these are saprophytes which can survive without nematodes
b. Sp which develop within the host and require nematodes for their
- increase probability that they will encounter a food source
- if you take a fixed quantity of fungi and look at # nematodes that are
attracted to the fungus
- the fast-growing ones do not attract them as much; they like them but
do not need them
- the parasitic ones attract them a lot more (see graph)
- it is related to the # of nematodes there
- the more fungi, the more nematodes (see graph)
- did an experiment (see graph)
- large amount when there is mycelium and conidia together vs. with
them separate
o this suggests that all parts of the fungus is producing
infochemical to tell nematodes to come so they can eat them
- when the nematode goes into the fungi, the fungi spreads spores onto the
- limited amount of nematode so the infected nematode do not respond as
much to other fungi which is a good strategy so the resource is not
- fungus canidia treated with an enzyme that could come with the fungus
reduction in response
Last slide on pg 3
A: spore
B: germinating spore
C: pre-symbiotic hypha from spore
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D: vesicle on host root
E: Arbuscule in cortical cell
F: Coiled hyphae in cortical cell
G: Mycelium growing from root into soil
Arbuscular mychorrhizal signaling: goes into the root, releases something,
and at the same time is absorbing nutrients
- spore germination caused by rhizomes?????
- plant has a system to defend itself from pathogens
- it is producing its own lactone that varies fungi responds to that, plant
detects signal and lets their guard down to let stuff in
- allows the whole process to occur to have the thing get into the plant
this whole process starts with infochemicals
- eg: parasital plants that take resources from other plants
- like bind weed- reduces photosynthesis of plants
- using diff chemical cues, have the bind weed and see which direction
they go
- Look at table 3.
o Looking at tomato plants and analyzed volatiles
o Must be using chemical cues emitted by host plants
o Relative proportions released in each host plant volatiles
o Then they laid artificial tomato plants with tomato volatiles
rates of release were way lower
- what happens if it is just moist soil, which direction does germination
No cue = random movement
20 day old tomato plant = leaning toward the host source
Pseudo tomato = significantly toward the source but not as much
- Bioassays: count how many went north/south
OR .. count how many went in 4 quadrats…
Which individuals chose the ½ of the disk with or without the volatile? Also
using quadrats?
- * are the ones that gave you results with direction
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- a lot of times people run experiments omitting results that do not fit their
Tomato plant with bind weed (Cuscula) parasitism
- compare the performance of having a caterpillar on control plants vs. bind
weed tomato plants; looked at volatiles
- with bind weed or caterpillar there were similar volatile levels
- changes over time
- also changes in how the plant behaves depending on what is around it
- If you look at amounts of volatiles emitted, when the bindweed is there,
there are low levels of volatiles
- caterpillars alone, high levels
- bindweed can manipulate the plant, use it for its own resources, but render
it less palatable
- not nutritionally lower quality, but the bindweed is making the plants
chemistry more attractive to bindweed but NOT to anything else like
caterpillars bc it is less palatable (caterpillars won’t want to lay eggs there)
With insects…
- monarch butterfly uses chemistry to decide where to lay eggs
There is a whole series of decision-making with respect to feeding behaviour
- a combination of how you integrate these signals depends on the internal
- stimuli from outside influences our decision to eat something…
- there is a fulcrum depends on circumstances THIS IS DYNAMIC
- eg: depends how hungry you are… if you are full, you won’t want to eat
- when they land on plants, do infochemicals and morphology fit its needs?
A rose is a rose is a rose G. Stein
- Is it? NO! Everything changes over time! There is variability!
- is every part of a leaf the same?
- Why do trees have variable parts? Light intensity, with shade or sun, have
branches and different leaves
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