Plant Defense Mechanisms

Herbivory

• Herbivory is any

damage to a plant

caused by herbivores

(organisms that eat

plants).

Types of Defenses

• Chemical

• Mechanical

• Thigmonasty

• Mimicry and Camouflage

• Leaf Shedding

A. Chemical DefensesTannins: give immature fruits a bitter

flavor. Example: Persimmon

Unripe Persimmon

Ripe Persimmon

Geranium

Foxgloves have compounds that can cause

paralysis or death when consumed.

Poison Ivy

Poison ivy produces urushiol—an oily chemical that discourages herbivory and produces a nasty rash when people contact it.

B. Mechanical Defenses

Raspberries and acacias have thorns to prevent herbivory.

Holly

leaves of holly plants are coated with waxes and resins (thick liquids that

harden into transparent solids) that make them slippery and difficult for

animals to eat

DandelionThe dandelion plant secretes latex (a milky sap) when its leaves are broken

which causes insect mouth parts to become very sticky.

Stinging Nettle

leaves and stem are covered with trichomes- hairs on the leaves with

hypodermic needles containing histamine—a chemical that produces a

stinging sensation

Coconuts have a very tough case

which surrounds the fruit.

C. Thigmonasty occurs when plants

move their parts to avoid herbivory

• http://en.wikipedia.org/wiki/File:Mimosa_Pudica.gif

• Example: Sensitive Plant

D. Mimicry/Camouflage

Stone Plant

• Resemble stones

• Inhabit desert southwest of America

E. Leaf Shedding

Some scientists think trees shed leaves to avoid parasites like gall-forming insects

Credits

• http://webecoist.momtastic.com/2010/02/15/deception-trickery-in-plants-12-masters-of-disguise

• http://image.shutterstock.com/display_pic_with_logo/409474/409474,1258702607,2/stock-photo-persimmons-

growing-on-the-tree-green-unripe-41252731.jpg

• http://www.texasbeyondhistory.net/adaes/images/persimmon-sm.jpg

• http://en.wikipedia.org/wiki/Mimosa_pudica

• http://kismetbrum.files.wordpress.com/2012/03/passionflower-2007-4.jpg

• http://wallpaperstock.net/autum-again_wallpapers_20233_2560x1600.jpg