In Joseph Priestley's experiments, which laid the groundwork for Ingenhousz's findings, it was demonstrated that light plays a crucial role in photosynthesis. Ingenhousz expanded on these findings, showing that when plants are exposed to light, they produce oxygen and consume carbon dioxide. Specifically, the correct relation would be:
Light is needed for a plant to give off oxygen, but not to give off carbon dioxide.
In the light, plants take in carbon dioxide and release oxygen as a byproduct of photosynthesis. In the absence of light, plants do continue to respire, which involves taking in oxygen and releasing carbon dioxide, but the production of oxygen is directly tied to the process that occurs in the presence of light.