MJ clones will root in just glass of water also...
so will ivy

so will most anything

from there is it just a crap shoot...

some plants definitley are ok with roots exposed to light and submerged in water.. go figure...

But MJ is not one of these plants...

although there are exceptions....

so...
the answer is.... best not to expose the roots to light..


Just like human.. some only like to procreate in the dark.. others like the light on...

: )