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BIOL 1902 Study Guide - Cardiac Glycoside, Umbel, Lignin

2 pages74 viewsFall 2011

Course Code
BIOL 1902
Michael Runtz

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Until ready for dispersal, plants protect the seeds
o Some use hard, heavily lignified structures, such as CONES
Some have HARD SEED COATS, such as those on ACORNS
These adaptations can be quite beautiful well as effective
Seeds can also be protected CHEMICALLY
Unripe berries are protected with TERPENOIDS (bitter tasting!)
o Aposematic coloration
Milkweed seeds are well protected by the pod, which is full of cardiac glycosides
In plants this process of sending out progeny into the world is called SEED DISPERSAL
o Advantages of seed dispersal
Avoids crowding and competition
Prevents spreading of disease or parasites
Prevents in-breeding
Once mature, the pods open and the seeds are off!
o How are seeds sent off?
Plants in open habitats such as old fields often use the wind
Wind dispersal = anemochory
In order to fly with the wind, seeds must have adaptations
o But no solution is perfect
o Problem: missing the target habitat
o Solution: produce lots of seeds!
Some plants harness the power of animals
Hooks and barbs catch on hair or feathres
o These seeds hitch-hike
Burdocks invented Velcro
Queen Anne’s Lace also uses animal power for seed dispersal
o Also protects seeds from rain
The umbel closes on cloudy days
Other sun-loving plants exploit animals in a very different way
Their seeds travel inside the berry(?)
Plant bribe animals with sweet food
Zoochory using animals for seed dispersal
Seed dispersal also takes place in very different habitats
Maple samaras (keys) are adaptations for dispersal!
Some tree seeds have sails to help them fly Basswood
Yellow Birch, tiny windblown seeds that land on stumps or logs Perched Birch
Some plants at ground level use the wind too Indian Pipe
SPRING EPHEMERALS also use a most ingenious seed dispersal strategy that involves
They pay animals with food
Food called ELAIOSOMES
They pay ants (myrmecochory)
Violet seeds also have ELAIOSOMES
But first they are dispersed from the plant
The pods shrink, squeezing out seeds one by one
Orange Jewelweed grows in wet places
Seeds are thrown several metres from the plant
o Jewelweed is also called “Touch-me-not”
Mitrewort Two spring ephemerals use yet another method of dispersal
They use raindrops
Splash cups of Bird’s-nest Fungus
Foamflower also uses raindrop and uses SPRINGBOARDS
Every habitat offers challenges
Many shoreline or aquatic plants have flotation devices on their seeds
Many plants can vary seed production bases on environmental conditions
o “boom or bust strategy”
Animal equivalent of seed dispersal is PARENTAL INVESTMENT
Temporary or EPHEMERAL PONDS are egg-laying habitat for Freeze-tolerant frogs
For some animals, the right host plant must be chosen
Eggs not guarded amphibians, reptiles, and insects
Soil temperature during egg incubation determines the sex of hatchling turtles

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