Could a metal detector be fine tuned enough to pick up a threshold of gold in a plant?
The two I own could not.
No way. There’s a tree, IIRC, in S. Africa that picks up nickel in large amounts, maybe with that, but it couldn’t be in a compound, it would have to be metallic.
I would think that the soil under an old deep-rooted deciduous tree would be rich in gold micro-particles. Probably not enough concentration to register with a standard detector.