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Lecture 6

BIOL 1902 Lecture Notes - Lecture 6: Phytoestrogens, Caffeine, Astringent

Course Code
BIOL 1902
Michael Runtz

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BIOL 1902 – Week 6
Protective elements in plants:
- Structural Elements (Cellulose, hemicellulose, Lignin, etc.) make plant tissues hard to
- Lignin = common in seed coats
- Silica: found in plants (e.g., horsetail)
-Other digestibility reducers aren’t structural components
oTannins = astringent
oPlant secondary metabolites (made by plant for defence)
-Other non-structural plant defences:
oTerpenoids taste bitter
Do not contain Nitrogen
oAsters contain Alkaloids
Alkaloids contain Nitrogen
Interfere w/ animal’s ability to digest food
Alkaloids found in caffeine, morphine, cocaine, nicotine
- Insect Growth Hormones
oMH = Moulting Hormone = ecdysone
oJH = Juvenile Hormone
oLarva 1st stage --------> Larva 2nd stage ---> Pupa ---> Adult
-Rock Polypody (fern) loaded w/ moulting hormones = phytoecdysones
-Brackern Fern loaded w/ phytoecdysones
oPhytoecdysones make insectss mature too quickly & die
-Balsam Fir contains phytojuvenile hormone
oInsects that eat plant w/ phytojuvenile hormones don’t mature
- Reproductive Hormones
oMess up animal’s reproductive system by creating phytoestrogens
oE.g. Red Clover – if sheep ate it, they may go infertile, have miscarriages
- Phototoxins
oVery nasty side effects
oE.g. St. John’s-wort – if animal ate it, phototoxins migrate near skin of animal,
make skin highly sensitive to UV damage
- Mustards advertise their defence (glucosinolates)
-Plants use aposematic colours too
oWhen fruit is maturing, but not mature yet, they have terpenoids around them,
which makes them bitter to eat
-When plant is under attack, alarm is sent to other parts to prepare themselves
oChemical messenger = phytohormones (jasmonic acid and/or ethylene and/or
salicylic acid) travel through plant, initiating biochemical responses
-Some animals pay ants for protection
oSome plants do too – Extrafloral nectaries provide food
-There are plants that when under attack, call “911” for help
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