All living creatures, plants included, are producing gaseous contaminants that may be harmful either to other living systems, man included, or even to themselves. Indeed, these contaminants have a tendency to accumulate when plants producing them are placed in closed environment such as a space station and/or planetary base. Therefore, a non-negligible part of Life Support Research and Development is dedicated to the degradation of these contaminants through physico-chemical or biological means.Radishes have been cultivated in the closed air loop bench of the Life Support Facility at ESTEC to verify that such a production of contaminants by plants existed. The production of nitrous oxide (N2O) by the radishes was clearly demonstrated when plants were grown under constant illumination. However, no production of such gaseous contaminant (N2O) was shown when the radishes were cultivated under an imposed light-dark cycle (LD:16/8). The metabolic origin of such a remarkable result is discussed.