2m, 4f
"Never knew why" as in you do now but didn't used to?
FWIW, plants "pearl" bubbles of oxygen. Plants produce O2 as a byproduct of photosynthesis. Underwater, this gas forms into bubbles until the bubble grows big enough to break free of the plant and float to the surface. This is called "pearling," and is a good sign of healthy, happy plants.