In a fish only tank they create surface agitation and therefore promote gas exchange and oxygenation. The down side is that this will release C02 very efficiently... great for fish, bad for plants.
In a planted tank, unless you're injecting CO2 your plants will absorb any CO2 present and want more. You also have plenty of O2 released. All that a bubble wall will do in a planted tank (besides looking nice) is to release CO2 before the plants can get to it.
in my nano i have no bubbles and little surface agitation. in my 10 gal i have a bubble wall and lots of agitation. i have a few low tech plant in there and plan to add more plants and less fake ones. no c02, ferts, or anything for that matter. should i cut the air?