[Boss]

You must almost all of the gasses in the atmosphere, or a replacement, in order to grow a plant. Oxygen is required absolutely. I don;t think it is so much that the plant needs it, but the organisms that create the nutrients as well as what the plant needs. I am sure you could get away with not having some trace elements, but only NASA would know that I think ;-)

Nitrogen (N2) 78 .080
Oxygen (O2) 20 .946
Argon (Ar) 0 .934
Carbon Dioxide
(CO2) 0 .038
Neon (Ne) 0 .00182
Helium (He) 0 .000524
Methane
(CH4) 0 .00015
Krypton (Kr) 0 .000114
Hydrogen (H2) 0 .00005