The \(Sansevieria\) \(trifasciata\), commonly known as the Snake Plant or Mother-in-Law’s Tongue, has long been a popular indoor houseplant. It is often celebrated for the supposed release of oxygen into a room throughout the night. This claim suggests it operates differently from most other plants, making it a favored choice for bedrooms. Understanding this requires examining the fundamental biological processes and the unique metabolic pathway this species employs.
The Standard Rules of Plant Respiration
Most common houseplants, such as ferns and many flowering species, utilize C3 photosynthesis. During the day, these plants open small pores on their leaves, known as stomata, to take in carbon dioxide (\(CO_2\)) and release oxygen (\(O_2\)). This process is dependent on sunlight to power the conversion of water and \(CO_2\) into sugars.
Cellular respiration, which converts stored sugars into energy for growth, occurs continuously, day and night. Respiration consumes oxygen and releases carbon dioxide. Because photosynthesis ceases in the dark while respiration continues, most plants are net producers of \(CO_2\) at night. This standard gas exchange causes a slight increase in carbon dioxide levels in a room with many typical plants once the lights go out.
Crassulacean Acid Metabolism (CAM) in Snake Plants
The Snake Plant belongs to a specialized group of flora that employ Crassulacean Acid Metabolism (CAM). This adaptation evolved primarily in arid environments, such as succulents, where water conservation is necessary. The CAM process separates the two main parts of photosynthesis by time instead of space.
The Snake Plant keeps its stomata tightly closed during the hot, dry daylight hours to prevent excessive water loss. This mechanism saves water but prevents \(CO_2\) intake. The plant waits until the cooler, more humid nighttime hours to open its stomata.
Once the stomata are open at night, the plant absorbs atmospheric \(CO_2\) and fixes it using an enzyme called PEP carboxylase. This enzyme combines the \(CO_2\) with other molecules to form malic acid, a four-carbon organic acid. The malic acid is then stored in the plant’s vacuoles until the sun rises.
During the daytime, when light energy is available, the stomata remain closed. The stored malic acid is broken down, releasing a concentrated supply of \(CO_2\) internally. This \(CO_2\) then enters the Calvin cycle to be converted into sugars.
The final, light-dependent steps of photosynthesis, which release oxygen, still occur only in the presence of light. Therefore, while the Snake Plant absorbs \(CO_2\) at night, its actual \(O_2\) production is a daytime event. The benefit of the CAM pathway indoors is that the plant actively removes \(CO_2\) when most other plants are releasing it, reducing the natural nighttime increase of carbon dioxide.
Indoor Air Purification Effects
Beyond the oxygen exchange cycle, the Snake Plant provides demonstrable benefits related to indoor air quality. Research, including the NASA Clean Air Study, focused on the plant’s capacity to filter harmful chemical compounds from the air. The leaves are effective at absorbing various Volatile Organic Compounds (VOCs) common in homes and offices.
This detoxification process is separate from photosynthesis and respiration, representing a distinct form of air purification.
Filtering Volatile Organic Compounds (VOCs)
The absorbed toxins include formaldehyde, which can be released by furniture, carpets, and cleaning products. The plant also helps remove benzene and xylene, two other VOCs found in plastics, synthetic fibers, and paints.
The removal of these VOCs is considered the most significant and scientifically validated air quality benefit of keeping a Snake Plant indoors. While nighttime oxygen release is often overstated, the continuous filtration of chemical pollutants contributes to a healthier indoor environment.