Question about toxicity of two poisonous plants.?

Question

I am taking a introduction to Botany class and I have to do a report on two poisonous plants.  The plants that I have chosen are the Castor Bean plant and Poison (or water) Hemlock.  I am having trouble locating some information for my report.  The castor bean is considered the most poisonous, but only the bean itself has the poison Ricin in it.  Why is it considered the most poisonous if only the seed is?  Also, there seems to be a debate as to what the lethal dosage is.  It's said to be anywhere from 1-8 seeds.  Since the level of Ricin varies in the seed, does anyone know truly how much will kill something.  If an animal or human were to ingest let's say 50 or 100 or 200 seeds, would that 100% kill that animal or person?  And since every part of the hemlock plant is poisonous, how come it's not considered the most poisonous.  I can't seem to find this information.  Any help is appreciated.  Thanks.

Marilyn · Accepted Answer

Check your library for a text titled "Poisonous Plants. Second Edition" by Dietrich Frohne and Hans Jurgen Pfander.  It's a handbook for Doctors, Pharmacists, Toxicologists, Biologists and Veterinarians.  Ricinus communis (Euphorbiaceae) info is on pages 183-189.  Conium maculatum (Apiaceae) info is on pages 39-41; 47-49.  

Your first task is to nail down definitions for "toxicity" and "poisonous".  For example: In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism. Legally and in hazardous chemical labeling, poisons are especially toxic substances; less toxic substances are labeled "harmful", "irritant", or not labeled at all.  In medicine (particularly veterinary) and in zoology, a poison is often distinguished from a toxin and a venom."  Only then can you proceed to discuss how toxic, dangerous or poisonous a substance is.  

Personally, I'd rate hemlock more dangerous than castor bean because all parts can cause illness or death depending on the amount consumed.  Adults have even died after eating birds that had been eating hemlock seeds.  Castor-oil plant is cultivated world wide for production of castor oil, which is used mainly for technical purposes, but also in medicine as a purgatory.  It may perhaps be considered more dangerous because more deaths occur per year due to it than due to hemlock  But, then again, there's more of it around.  Again -- how do you measure dangerous?

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Question about toxicity of two poisonous plants.?

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