BIOA02H3 Lecture Notes - Lecture 12: Trichome, Herbivore, Starch
27 Apr 2018
School
Department
Course
Professor
BIO A02 – Module 1 Notes Hassan Alibhai
Plant Form and Function Page 52
Plant Defence
•Plants feed the world, all non-plants depend on plants for food
◦Every plant is under constant attack from herbivores (animals eating plants is actually the
most common plant-animal interaction)
▪Many insects (largest herbivore group) are very small, and so it may not be very visible.
Primary and Secondary Compounds
•Primary Compounds => necessary for plant
survival => photosynthesis, proteins, starch,
cellulose (plant will not reach maturity without
these)
•Secondary Compounds => no known direct
function in basic metabolism
◦Various types of compounds, strict control of
synthesis
◦Spices and food
Types of Plant Defence
Mechanical Defence Chemical Defence Systemic Defence Induced Defence
•“Physical”
•Plants grow
organs or tissues
that fend of
animals that
want to eat them
•Somewhat slow
to react
•Toxins and
poisons that fend
off insects
•Immediate,
quick to
mobilize
•Use secondary
compounds
•Defence is
always present
◦Normally
physical due
to the need
of organs and
tissues (not
fast)
•Defence only
acts when the
herbivore attacks
◦Normally
chemical,
just
triggering
reactions
Systemic Mechanical Defence
•Thorns and spines => can cause infection or death for small insects
•Trichome density
◦Trichome => specialized cells in the epidermal tissue that normally
shield plants from the sun and prevent major moisture escape
◦Small caterpillar – must first remove dense trichomes, (no
nutritional value), will feed on less dense leaves
•Mimicry “make-believe” => plant sacrifices photosynthetic surface
◦Passionflower makes yellow “eggs” that are fake, (can be 3-D)
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BIOA02H3 Full Course Notes
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