How Red and Far-Red Light Ratios Impact Plant Development

Posted by Brian Sparks|January 27, 2022

Light quality in greenhouses varies both seasonally and daily as weather conditions and the atmospheric path traveled by light impacts the absorption and scattering of different wavelengths, resulting in a discrepancy between pure sunlight and what reaches the plant canopy.

Considering spectrum in terms of photon ratios has made it easier to study the impacts of light quality on plant growth and development, with the main ratios of interest being red to blue (R:B) and red to far-red (R:FR). Researchers are also beginning to study blue to green (B:G) and blue to far-red (B:FR), among others.

Understanding the morphological impacts of different photon ratios allows growers to harness these ratios as a tool to guide plant development. For example, the ratio of R:FR light has been extensively studied due to its impacts on stem elongation, apical dominance, leaf expansion, photosynthetic efficiency, and flowering response in short-day and long-day plants. Controlling the R:FR ratio thus allows control over plant morphology architecture.

To better understand the significance of this innovation, Sollum Technologies has developed a whitepaper that focuses on plant photoreceptors and the R:FR ratio.

“While the impact of light quantity may appear more obvious, that of light quality is more abstract due to the nanoscopic nature of light,” says Rose Seguin, agronomist with Sollum Technologies. “With light quantity, we can easily discern whether light is more intense and whether the day is longer or shorter. With light quality, we are considering the spectrum thus the decomposition of light into different colors, their wavelengths, and the relative amounts of each wavelength.”