Imagine that a researcher claimed to have created a genetically modified plant that produces twice as much energy as it harnesses from its environment. how could this be possible

According to the Law of Conservation of Energy, energy is neither created nor destroyed. Technically, it is impossible for the plant to produce energy twice this input. It could only be possible if an external energy is required to create a reaction that would create more energy. This external energy could in the form of energy or another chemical containing potential energy.