At night, of course, there is no sunlight, and the moon does not provide enough light to drive the reactions of photosynthesis. Essentially no oxygen escapes from the leaves, and so the forest air is no longer enriched in this gas that is essential for our own life.
If we look a bit more carefully, however, we will see that plant photosynthesis and respiration are actually not entirely separated by the daily light/dark cycle—during the daytime they coexist. Remember, photosynthesis only takes place where there is chlorophyll, i.e. in the green cells of the leaves or needles. What about the rest of the plant—the stems, the roots, all the living cells that do not contain chlorophyll? They get sugar from the chlorophyll-containing cells. In fact, even the cells that photosynthesize also respire! You might say that the plant feeds itself the food that it itself has made, so that every one of its living cells can generate metabolic energy day and night without interruption.
Final Night of “Photosynthesis” - Marin Matters - …
While its trees have their leaves, a deciduous forest, like an evergreen forest, reverses its breath on a daily cycle. During the day, while photosynthesis works faster than does cellular respiration, a deciduous forest primarily breathes in carbon dioxide and exhales oxygen. During the night, when photosynthesis stops but cellular respiration continues unabated (not only in green plants but also in the myriad other organisms that compose the forest ecosystem), the forest breathes in oxygen and exhales carbon dioxide. Once the leaves are gone, however, it only breathes in oxygen. At that point, it no longer matters whether it’s day or night—the trees respire without photosynthesizing. They always take in oxygen and release carbon dioxide, just like you and I do.