Final answer:
In the absence of sunlight, plants still produce small amounts of carbon dioxide through the process of cellular respiration, which does not require light.
Step-by-step explanation:
Even in the absence of sunlight, plants can still produce small amounts of certain substances, particularly carbon dioxide (CO2), through cellular respiration. Unlike photosynthesis, which requires sunlight to convert carbon dioxide and water into glucose and oxygen, cellular respiration occurs continuously in cells, both day and night, releasing energy by breaking down glucose and other molecules. This process not only produces energy (ATP) for the plant's cellular activities but also leads to the production of carbon dioxide and water as byproducts.
Therefore, while sunlight is essential for photosynthesis and the production of glucose, plants remain metabolically active in its absence, utilizing the glucose they have stored to maintain vital functions. Even when not exposed to light, they continue to consume oxygen and produce carbon dioxide, highlighting the ongoing metabolic processes within plant cells.