Let's say it's sometime in the future, and humanity has expanded outwards into the solar system, and we've genetically engineered some really big plants that can for some unimportant reason, survive in the vacuum of space. These plants float around and preform photosynthesis, much like any other plant, absorbing sunlight and pumping oxygen out into the void. which they can do despite the complete and utter lack of any other usable atmospheric gasses or livable conditions, Because Reasons.
What happens to this oxygen? is it possible for this to lead to a breathable (if extremely thin) atmosphere in space? Would the oxygen pool up around celestial bodies, or the plants themselves? would any atmosphere get swept away by solar wind/the motion of the solar system as the galaxy rotates? Would this solve any of the other problems of floating exposed through space besides air? (radiation, freezing, etc)