Plants not only improve air quality but protect from viral and bacterial infections as well

A new study published in Research Square suggests that plants are not just involved in cleaning but may also be protecting us from COVID, cold and other viral & bacterial diseases.

Despite the fact that many of the mechanisms by which plants maintain the biogeochemical cycles and the quality of the air are still poorly understood. Hydrogen peroxide (H2O2) has recently been reported to be produced spontaneously when water vapor condenses into tiny droplets. Here, Saman Samadi and colleagues describe the detection of H2O2 near plants that were engaged in photosynthesis in a confined environment.

To study this, the researchers placed a plant, originally Saintpaulia ionantha, in an airtight container. The soil surface of the pots was covered with foil and the plants were placed in watertight and airtight polyethylene chambers. In experiments using peroxide test strips, the strips are attached to the leaf surface of the plant or placed at a specific distance from the leaf surface of the plant to study spatial heterogeneity. A commercial LED plant growth lamp was then used to expose the chamber to varying intensities of light. Light intensity was measured with an LCA-4, a handheld reef chamber gas analyzer. The relative humidity and temperature inside the chamber were monitored. Plants were left in a lighted chamber for 1.5-8 hours. The chamber was then opened and strips or condensate he collected for H2O2 analysis. Controls include: A room without plants. A room in which plants are present but protected from light. A room with plants and light but no plant leaves. All experiments were performed in duplicate.

The key findings of this study were:

1.A sharp drop in H2O2 concentration was observed after 2 h, suggesting that the generated H2O2 is reduced to H2O by cleavage of weak peroxide bonds or photochemical reactions.

2.Alternatively, the reduction in H2O2 could be the result of redox reactions with plant-mediated VOCs (not measured). Comparing light intensities, medium intensity (385 µmol m-2 s-2) yields higher measured H2O2 concentrations (2.2 ≤ 0.2 ppm) than low light intensity (230 µmol m-2 s-2) was observed, or high light intensity (600 μmol m-2 s-2, 0.8 0.0 ppm).

3.Saintpaulia ionantha can be saturated with light of medium intensity.

4.Alternatively, the low H2O2 concentration observed at higher light intensities is the result of faster RH saturation, leading to a rapid drop in H2O2 concentration, as previously described.

Reference:

Samadi, S., Sharifyazd, S., Cabling, L., Dekker, I., Hawkins, B., & Dubrawski, K. (2023). Spontaneous generation of exogenous hydrogen peroxide by plants. Research Square Platform LLC. https://doi.org/10.21203/rs.3.rs-2635805/v1