Why do certain plants produce ricin?

Answer 1

Most plants produce something that is toxic to something else. In general a plant would produce toxins to counteract attacks on it (animals, insects etc.). Some specialized eaters would simply digest poison unharmed, where as others who eat the poison would be so ill that they stopped eating or even died.

The poison in plants vary.

Some produce Nicotine (Tobacco) and others produce Caffeine (Coffee). As a paradox of these plants self defense methods, we humans actually inhale and drink these and seem to enjoy it.

However, we would not get the last laugh if we tried our digestive system against plants producing Ricin. 0.5 Milli Gram is considered deadly dose for an adult human being. That is no more than 1-3 seeds of the Castor Bean plant

Ricin is however not the most dangerous compound/poison that exist naturally. Botulinum Toxin made by a bacteria is so lethal that only 90-270 Nano Gram is considered deadly dose for an average 90 kg person.

Ricin is a water-soluble protein that inhibits protein synthesis in animal cells, leading to their death. Seeds from the Castor Bean plant are bad news if eaten. One seed can kill a child. We are not the only sensitive animals. Four seeds will kill a rabbit, 5 a sheep, 6 an ox or horse, 7 a pig, 11 a dog, but it takes 80 to kill a duck. Ricin has been investigated for its potential use as an insecticide. There are some potential medicinal uses for ricin, since it is so cytotoxic. It might be useful in bone marrow transplant procedures, and as an anti-tumor agent.

It does not take long for to-days scientists to find a possible use for most "unwanted" compounds in plants and turn them "most wanted". Even Botulinum Toxin has found its way into medicine and is nowadays used in the drug Botox that is injected in order for some people to reduce wrinkles and look younger.

The plants want to protect themselves and we humans are not long to find a use for it.