Spotted_Blewit

What's the difference between truffles and mushrooms? Why are truffles so hard to grow in captivity?

They are both types of fungi. "Mushroom" is technically the name for a fungus with a stem and a cap (so it refers simply to the shape of the fruit body). Large fungi are split into two large groups according to some microscopic features of their spore-producing parts. The biggest one are the basidiomycota, which contains all of the mushrooms and most of the other larger fungi. The other one is the ascocmycota, which contain various oddities like cup fungi and morels (which look like brains on sticks). Truffles are a specialised type of fungus in the ascomycota which have evolved to fruit underground and smell strong - they are "designed" to be dug up by animals and eaten, and the spores then survive passing through the gut of the animal, which is their dispersal method. This is highly unusual - nearly all other fungi use wind to disperse their spores.

They are hard to grow because they are symbiotic with trees and the partnership between fungus and tree has to happen in just the right way at just the right time. Replicating this process isn't easy, and it takes several years before you find out whether it has worked.

Nearly all of the cultivated species of fungus are saprophytes - they feed on dead matter, rather than being symbiotic with plants. This means you can sterilise their food and eliminate the spores of competing fungi. It is much harder to do this with symbiotic fungi because you cannot sterilise the forest floor.

Are there any mushrooms that are poisonous but also extremely delicious? You know, the kind of thing that might make you say, 'Well, I'm going to be a firehose from both ends for the next three days, but

damn

that sandwich was worth it'?

The most dangerous poisonous mushroom in the world (the Deathcap, Amanita phalloides) is supposedly quite tasty, according to one lady who had eaten one by mistake and died a few days later. It has some good edible relatives, so this isn't surprising.

There are also some fungi that have been highly regarded as food for a long time, before eventually people realised they were poisonous. This includes the Brown Rollrim (Paxillus involutus), which people used to believe was edible when cooked but mildly poisonous raw, until they realised that long-term consumption leads to a massive allergic reaction and then death. It also includes two species in the genus Tricholoma (T. equestre and T. terreum) which are now known to be responsible for deaths by a mechanism called rhabdomyolysis (rapid breakdown of muscle tissue leading to kidney failure). T. equestre is known as "Yellow Knight" or "Man on Horseback" and was so esteemed that in France it was reserved for the nobility (Knights). Another one is Angel's Wings (Pleurocybella porrigens), which was highly regarded until implicated in many poisonings in Japan - it causes brain damage, but only if you eat a lot of it and you have dodgy kidneys.

Why do some mushrooms turn blue when bruised? I've seen psilocybe and bolete mushrooms that do this.

It's an oxidation process. The most spectacular colour changes happen to some boletes when cut open:

https://www.flickr.com/photos/orangebuzz2000/9684438093

I have come across a few people with this allergy. It is uncommon, but not unheard of.

What is the most lethal mushroom? How quick does it harm you?

Deathcap (Amanita phalloides) and a few very close relatives (notably the Destroying Angel (A. virosa)). A handful of other fungi contain the same toxins, but are less common and less easily confused with edible species.

They initially cause very serious gastric symptoms, lasting 2 or 3 days. After this the victim feels like they are recovering, but the toxins are destroying the basic biochemical mechanisms in their liver and kidney cells (they interrupt the pathway by which the cells turn DNA into proteins, which kills the cell in a few days). Death results from liver and/or kidney failure within ten days, usually faster.

Some other fungi contain toxins that cause heart/lung failure within hours, but you have to eat quite a lot of them to die. One Deathcap is more than enough to kill an adult human,