yes however the levels that it is found in human blood is so low that it may have a very subtle effect. not like doses you have when you dose yourself.

plants also respire the same way we do.

they dont figure it out in the sense that you and I figure out that by touching something hot you get burned. plants learn through death and reproduction. that is their way.

the point is DMT is an easy molecule to make (biosynthetically) and it happens to interact with the nervous system of a large spew on animal life. to humans we can tolerate a high dose and even like it. to another animal or insect it may be very disturbing to have such weird alterations or deadly in the case of insects. nicotine is dangerous to insects as well (but lots of people love it). that is part of the role these compounds play.

the only point in trying to make is that just because LSD is an active compound in humans does not mean it is made in nature. i am not trying to bash you or insult your ideas I am just trying to help you think a little more about what you are saying and learn a bit more about plant and fungal secondary metabolism because it seems to be something you are interested in.