Since oxygen is a gas, it encompasses the container it is in, if you could get an ample supply of carbon dioxide to feed the plant the atmosphere would still be to thin to survive, while that area near the tree would be more oxygen rich, not thick enough. Plus you would use the oxygen faster than the tree could produce. A better scenario would be Lichen, getting pools of water in craters to grow them, and tending it till it created it's own ecosystem, but the would involve creating a sustainable food chain to support this growth, in the long run you could terraform the moon.