| MadSci Network: Botany |
Yes, plants do have a net release of carbon dioxide at night due to cellular respiration. Both animals and plants undergo cellular respiration constantly. However, in the light, plants produce much more oxygen via photosynthesis than than they consume in cellular respiration. Nonphotosynthetic plant parts, such as potato tubers and apple fruits, would give off carbon dioxide even in the light. You would need a very poorly ventilated room and a lot of plants in order to produce a toxic level of carbon dioxide at night.
Try the links in the MadSci Library for more information on Botany.