1. Respiration: Even in the absence of sunlight, plant cells continue to respire. This process uses oxygen and releases carbon dioxide as a byproduct.
2. Diffusion:
* Oxygen: Oxygen produced during respiration diffuses out of the cells into the intercellular spaces and ultimately into the atmosphere through the stomata.
* Carbon Dioxide: Carbon dioxide produced during respiration diffuses from the cells into the intercellular spaces. It then moves through the stomata, but at a much slower rate than during the day because the stomata are partially closed in the dark.
3. Factors affecting gas exchange in the dark:
* Stomata: The degree of stomatal opening plays a major role in controlling gas exchange. In the dark, stomata typically close partially, limiting the rate of gas diffusion.
* Temperature: Higher temperatures increase the rate of respiration, which in turn increases gas exchange.
* Water availability: Plants need water to carry out respiration. If water availability is low, respiration will be limited, and gas exchange will be reduced.
In summary:
* Respiration is the main driving force for gas exchange in the dark.
* Gas exchange is slower than during the day due to partially closed stomata.
* Factors like temperature and water availability influence the rate of gas exchange.
Note: It's important to remember that the net gas exchange in the dark is typically negative, meaning the plant is consuming more oxygen and releasing more carbon dioxide than it takes in. This is because respiration is the dominant process in the absence of photosynthesis.
