A phytotoxin is a poison produced from what?

A phytotoxin is a poison produced by plants. The word combines phyto-, meaning “plant,” with toxin, meaning a poisonous substance. In its common biological sense, a phytotoxin is a chemical made by a plant that can harm animals, microbes or other organisms.

Plants cannot run away from insects and grazing animals, so many species use chemical defenses instead. These compounds may make the plant taste bitter, interfere with digestion, damage nerves or disrupt other biological processes. Examples include nicotine in tobacco, caffeine in coffee and tea, and certain toxic alkaloids found in plants such as deadly nightshade.

The term can also be used more broadly for substances that are toxic to plants, including some chemicals produced by microorganisms or used as herbicides. That secondary usage can cause confusion, but a straightforward quiz asking what produces a phytotoxin is referring to plants themselves.

Not every poisonous plant chemical is equally dangerous in every dose. Toxicity depends on the compound, the amount consumed, how it enters the body and the biology of the exposed organism. Some plant toxins have even become useful medicines when carefully controlled.