UC Riverside researchers discover how plants automatically protect themselves from solar surges

University of California, Riverside researchers have discovered that, during photosynthesis, plants can protect themselves from solar surges and achieve near quantum efficiency when converting light into energy by absorbing specific colors of light.

“Our model shows that by absorbing only very specific colors of light, photosynthetic organisms may automatically protect themselves against sudden changes – or 'noise' – in solar energy, resulting in remarkably efficient power conversion," said Nathaniel M. Gabor, an associate professor of physics and astronomy, and leader of the study, which was published in the Journal Science on June 26, 2020. 

"Green plants appear green and purple bacteria appear purple because only specific regions of the spectrum from which they absorb are suited for protection against rapidly changing solar energy," Gabor said.

Plants do not absorb light at the peak of an idealized absorption spectrum. Instead their absorbers (chlorophyll a and b) are off-set from the peak and separated for minimizing excitation noise. In this study the researchers borrowed from the field of network science to develop a model that accounts for this "absorption-peak pattern." It is this specialized system that allows plants to "mitigate internal and external fluctuations in energy transfer, minimizing noise in output power," thereby protecting the plants from harm.

The researchers compared their noise-cancelling network model predictions to the actual absorption spectra in three different environments. The three tested environments included full solar exposure, light filtered under sea water and light filtered by oxygenic phototrophs. What they found is that for each environment their model accurately predicted the plant absorption spectra in the different environments.

The researchers remarked that they were surprised about the degree to which they were able to reproduce the photosynthetic spectra with their model. They said this suggests “an underlying organizing principle for light-harvesting systems.”