i believe because you need to put the tube ABOVE the plant, so it can get to all the fan-leaves. Roots use Oxygen, leaves use CO2
that said, with a single plant, i wouldn't get too risky/frisky with it, ya know? If you had a couple, you could screw around with one...
I have worked on a big plant with aerogarden (not advised) and haven't had too many problems. I have been through that problem you had with leaf burn. For me it was the lights included in the set. If they get too close the plant stresses out.
As far as the sex of your plant goes, it seems to be mostly genetic. I did read in a separate forum on here that humidity and temperature control can help you raise your odds of getting a female.
The female that I have doesn't smell, (prob specific to the strain), but the male I did have was stinky. Save your pollen from the male if you end up with one and use it with a pollen press. Hash is definatly not something to miss out on!!
Overall in my 7 month grow test - I have found that regulation of the nutrients is very important. If you dont have enough the leaves get weak and wilt. If you get too much you get root burn and other leaf burn problems.
I have been using the included lamp and the aerogarden herb nutrients (high in nitrogen for beginning part), and aerogarden flowering tablets (for flowering - high in P(something) cant remember the word im looking for.)
good luck - your plant is looking premo
