I was reading this fascinating article about how sleep evolved before brains, and it got me thinking "can plants sleep" and "what is sleep anyway".

A line in the article states:

Studies by a team in South Korea and Japan showed that the hydra periodically drops into a rest state that meets the essential criteria for sleep.

But after looking around I am unable to find the "essential criteria for sleep" - Before I am able to answer questions like "can plants sleep" I think I first need to understand what this essential criteria for sleep actually is.

Can anyone here help me out? Many thanks in advance.

I was reading this fascinating article about how sleep evolved before brains, and it got me thinking "can plants sleep" and "what is sleep anyway".

A line in the article states:

Studies by a team in South Korea and Japan showed that the hydra periodically drops into a rest state that meets the essential criteria for sleep.

But after looking around I am unable to find the "essential criteria for sleep" - Before I am able to answer questions like "can plants sleep" I think I first need to understand what these essential criteria for sleep actually are.

Can anyone here help me out? Many thanks in advance.