I had assumed they had grown the plant between two vertical, parallel panes of glass.

That would probably produce a distorted image of the root system.

On the contrary - I think you'd get an accurate image of a very distorted root system!

	▲	JumpCrisscross 7 hours ago \| parent [-]
		> you'd get an accurate image of a very distorted root system At the very least, you've taken a 3D system and reduced it to 2D. Additionally, you're exposing not only the root system but the entire microbiome around them to light and, almost certainly, unless you were incredibly meticulous about sealing, oxygen.