Phys Eco Exam 1 Plant defenses and allelochemicals #6

What are examples of physical plant defenses?

Spines and thorns, such as those of cactus and acacia.

What are allelochemicals?

Chemicals involved in interactions between plants and herbivores or between plants.

How can allelochemicals affect herbivores?

As deterrents that reduce palatability, toxins that are poisonous, or digestive inhibitors.

Quantitative vs. qualitative plant defenses

Quantitative: high quantity (~5% dry leaf weight), dose-dependent, generally reduce digestibility. Qualitative: very small quantity (<1%), all-or-nothing effects, generally toxins or deterrents.

What are alkaloids?

Compounds containing at least one nitrogen-containing ring that often affect the CNS. Examples include opium, caffeine, and nicotine.

What are pyrrolizidine alkaloids?

Compounds hydrolyzed into toxic compounds by mammals but sequestered by some moths for predator deterrence/warning coloration and used by butterflies to make pheromones.

What are cyanogenic glycosides?

Compounds that produce hydrogen cyanide when consumed.

What are cardiac glycosides?

Compounds such as those in milkweed that are similar to digitalis. Monarch butterflies consume them, which helps deter predators such as blue jays.

What is aposematic coloration?

Warning coloration associated with defenses such as toxic compounds.

What does oxalic acid do?

Binds calcium in the body and can induce deficiency; cactus and rhubarb were examples.

What is locoweed?

A plant noted as deadly to grazing sheep in the U.S.; woodrats were also mentioned in association with it.

How does lignin act as a plant defense?

It occurs in the cell wall and reduces cellulose digestibility.

Where were terpenes mentioned?

In conifer needles.

What are the functions of tannins?

They occur in vascular plants, protect against viruses/bacteria/fungi, protect seeds, deter herbivory, and reduce digestibility by binding plant protein and/or interfering with digestive enzymes.