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Uptake and in-plant transport of formaldehyde by six plants with or without soil microorganisms were investigated. The capabilities of fresh and boiled leaf extracts to dissipate added formaldehyde were also measured to evaluate formaldehyde metabolism in plant tissues. Results show that when the initial formaldehyde level in air was 0.56 ± 0.04 mg·m

In 2012, 7 million premature deaths were attributed to air pollution, of which 4.3 million to indoor air pollution inducing the “sick building syndrome.” In particular, formaldehyde, a toxic and highly reactive chemical, has been linked to cancer. The use of soil microbial biomass and plants to remove formaldehyde from polluted air by plants has been proposed, but there are so far few quantitative reports. Here, we developed an efficient plant–microbe technology to remove formaldehyde by adding cultured microorganism into the rhizosphere of three plant species, Tradescantia zebrina Bosse (T. zebrina), Aloe vera (Haw.) Ber (A. vera) and Vigna radiata (Linn.) Wilczek (V. radiata). Shoots were exposed to 0.72 mg of formaldehyde per m3 of air for 24 h. Results show that formaldehyde removal rates were 23.1 ± 0.1 μg/h/g fresh weight with microbes versus 18.5 ± 0.21 μg/h/g without microbes for A. vera, 86.4 ± 0.7 versus 59.3 ± 0.2 μg/h/g for T. zebrine and 97.6 ± 0.9 versus 25.1 ± 4.2 μg/h/g for V. radiata. Overall, formaldehyde removal was increased by 6.7–90.5% using microbes. Formaldehyde removal was influenced by light intensity, with this effect more pronounced in plant–microbe systems.

Indoor potted plants played an important role in the removal of air-borne VOCs. According to the difference between plant fresh extracts and boiled extracts on breakdown ability to the added formaldehyde, a simple quantitative evaluation method was used to identify the mechanisms of formaldehyde removal from the air by wild Taraxacum mongolicum Hand.-Mazz. and Plantago asiatica L.. After shoots exposure to formaldehyde (1.28 mg/m3 in the air) for 24 h, the formaldehyde removal rates of P. asiatica and T. mongolicum were 73.18 and 121.20 mg/h/kg FW (fresh weight), respectively. Formaldehyde can be transported from the air to the rhizosphere solution by plants, and the maximum rates of transmission by T. mongolicum and P. asiatica were 23.73 and 83.08 mg/h/kg FW, respectively. Although plant metabolism was responsible for formaldehyde loss in the air-plant-solution system, and the metabolic activity depended on the enzymatic and redox reactions in the plants, P. asiatica and T. mongolicum are still good candidate species for developing phyto-microbial technologies. The redox reaction was the main mechanism used by P. asiatica shoots to dissipate formaldehyde, while the enzymatic reaction was the main mechanism used by T. mongolicum. The higher oxidative potential and lower defensive enzyme activity in P. asiatica shoots led to its higher formaldehyde removal rate compared to T. mongolicum. Meanwhile, the stronger redox reaction ability in the T. mongolicum roots was partly responsible for its lower formaldehyde transmission rate. The results show two plants have strong tolerance to formaldehyde in the air and good formaldehyde removal ability.

Self-enhancement effect of potted Chlorophytum comosum on formaldehyde removal from air and its mechanism were investigated by measuring the formaldehyde removal rate and its oxidative potential in leaf extracts with an increase in shoot exposure time. Results showed that the main mechanism of formaldehyde removal by potted C. comosum was the accumulation by plant tissues and the breakdown therein. With a 74-h shoot exposure, 68 and 94% of formaldehyde loss in air were dissipated by plant tissues when the initial level in air was about 1.22 and 2.64 mg m−3. Leaf extracts of C. comosum could effectively dissipate (added) formaldehyde, and the dissipative capability increased with the time of shoot exposure to formaldehyde in air, which corresponded to an increase in oxidative potential of the leaf extracts. By comparing the dissipation capabilities of fresh-leaf and boiled-leaf extracts to added formaldehyde, the redox reaction between oxidative matters in plants and reductive formaldehyde might be the main mechanism on the formaldehyde breakdown in plants. With increasing initial formaldehyde concentration in extracts, the contribution of enzymatic reactions (such as dehydrogenase) to dissipate added formaldehyde decreased sharply, corresponding to an increase in the redox reaction. A burst in ROS (reactive oxygen species) induced by formaldehyde exposure could enhance the capability of C. comosum to remove formaldehyde from air, suggesting that a further increase in formaldehyde removal by plants could be accomplished by increasing the oxidative potential in plant leaves.

The roles of enzymatic reactions and redox reactions caused by reactive oxygen species (ROS) in formaldehyde metabolism in tomatoes and wheat seedlings and the changes in peroxidase (POD) and catalase (CAT) activities in plants were investigated. Differences in the breakdown of added formaldehyde between fresh and boiled plant extracts were determined to calculate the contributions of different removal mechanisms. Two plant seedlings efficiently removed formaldehyde from air when its level varied from 0.65 to 1.91 mg m