Recently, there was a post on Reddit asking about why Nirnroot chimes. A respondent pointed to a older post on the TESOLore subReddit for an answer.
A conclusion from an analysis of the lore on the subReddit by one member speculates that,
The Nirnroot is another cousin of the Hist, like the Sleeping Tree and the Umbrielian Hist. It shows far too many signs of being related to not be related. It’s not nearly as smart/sentient as the Hist or even the Um-Hist, but it has the wherewithal to enter a state of dormancy when times get rough.
Hmm…