Light converting films accelerate plant growth

Plants convert visible light to energy via photosynthesis. In addition to visible light, sunlight also contains ultraviolet light. Researchers in this study aimed to provide plants with additional visible light to use in photosynthesis by employing a wavelength converting material (WCM) that can convert the UV light into red light. They developed a WCM based on a euro­pium complex and made a thin-film coating that can be applied to commercially available plastic sheets. They not only showed that the film converts UV light to red light, but also that the film does not block any of the bene­ficial visible light from the sun.

The film was then tested by comparing plant growth using sheets with and without the WCM coating. Trials were performed for both Swiss chard, a vegetal plant, and Japanese larch trees. In summer, when days are long and sun irradia­tion is strong, no signi­ficant difference was observed for Swiss chard when using the WCM films. In winter, however, when days are shorter and sunlight is weaker, Swiss chard plants grown using the WCM films showed 1.2 times greater plant height and 1.4 times greater biomass after 63 days. The researchers attri­buted this acce­lerated growth to the increased supply of red light provided by the WCM films.

Trials involving Japanese larch trees also showed accelerated growth. Seedlings showed a higher relative growth rate in the initial 4 months of growth, resulting in a stem diameter 1.2-fold larger and total biomass 1.4-fold larger than trees grown without the WCM coating. Critically, this enabled the seedlings to reach the standard size for planting in the forestry of Hokkaido within one year. Use of WCM films could shorten the growth period of seedlings from two years to one year, resulting in more cost-efficient plant production. This techno­logy also has the potential to help with food security issues in colder climates and is beneficial because it does not require any elec­tricity to operate. Researchers see the customiza­bility of the technology as especially promising.

“By using a coating of wavelength changing material, we were able to successfully create a transparent film and demons­trate its ability to acce­lerate plant growth,” said Sunao Shoji. “By rationally designing the light-emitting ion, we can freely control the color of emitted light to be other colors like green or yellow, so we expect to be able to create wavelength converting films that are optimized for different plant types. This opens a large avenue of future develop­ment for next generation agricultural and forestry engi­neering.” (Source: Hokkaido U.)

Reference: S. Shoji et al.: Plant growth acceleration using a transparent Eu³⁺-painted UV-to-red conversion film, Sci. Rep. 12, 17155 (2022); DOI: 10.1038/s41598-022-21427-6

Link: Faculty of Engineering, Hokkaido University, Sapporo, Japan