Most green plants do not carry out the light-driven reactions of photosynthesis in darkness because those reactions require light energy. However, plants keep respiring around the clock, using stored sugars to power living cells.
The daylight process
In chloroplasts, light captured by pigments drives chemical reactions that help build carbohydrates from carbon dioxide and water. The energy for that step comes from light, so ordinary plants cannot sustain it in total darkness.
What plants do at night
Cells continue cellular respiration, a process that releases usable energy from stored organic molecules. Growth, repair and transport may continue even after the lights go off. A plant does not become biologically inactive at sunset.
An important exception to simple explanations
Certain drought-adapted plants using CAM metabolism take in and store carbon dioxide at night, but they generally use daylight to run the energy-dependent parts of photosynthesis. Nighttime carbon uptake is not the same as performing the entire process without light.
Should houseplants have light all night?
Most houseplants benefit from a normal day-night rhythm. Provide enough appropriate light by day rather than assuming constant illumination is always healthier. Species differ in light needs and photoperiod responses.
Frequently asked question
Do plants take in oxygen at night?
Plants use oxygen for cellular respiration day and night; the overall gas exchange also depends on daylight photosynthesis.
Sources and further reading
See this university, government or veterinary source for more information.
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