i forgot to add some examples for small pots and peppers in my previous post, i kinda specialized in that direction:
8l, or 2 gal
a butch t scorpion,7l or 1.8 gal
4l or 1 gal
3l, or 0.8 gal
and if productivity is in question (because previous pics were taken right before cutting the plants down before winter), this is a chocolate bhut jolokia:
so yeah, it's possible and even easy. this is also the reason peppers do incredibly well in hydroponic setups, a guy in Finland grows 4m tall pepper trees in 30 cm deep hydro tubs,its insane.