Colour blue could be key to greener future

The plant Begonia pavonina is known for its strikingly blue, irridescent leaves, previously assumed by scientists to be purely ornamental. A recent paper published in Nature Research, however, concludes otherwise – that these qualities enhance photosynthesis in low light. The findings have implications for how we understand chloroplasts and also points to exciting new possibilities in solar energy capture techniques for low light conditions.

Chloroplasts are usually green and considered to be passive in their conversion of light into chemical energy. Thylakoids, the membrane-bound compartments they contain, are stacked on top of each other in an irregular way. But in the chloroplasts in Begonia pavonina, the UK-based research team discovered, the thylakoids are stacked fare more regularly, creating photonic crystals that reflect blue light strongly, giving the leaves their distinctive colour and iridescent glow. More importantly, the researchers believe that ‘This structure enhances photosynthesis in two ways: by increasing light capture at the predominantly green wavelengths available in shade conditions, and by directly enhancing quantum yield by 5–10% under low-light conditions’.

These photonic properties may be more widespread in plants than is currently realised, including in plants that do not show any obvious signs of iridescence to the naked eye. The team concluded that ‘Chloroplasts are generally thought of as purely photochemical; we suggest that one should also think of them as a photonic structure with a complex interplay between control of light propagation, light capture and photochemistry’.

One of the researchers later highlighted the potential this research has for the development of solar energy capture techniques that can work in low light conditions. ‘Nature has found a way to combine structure that manipulates light with the light harvesting machinery’, he said. ‘This is rather novel in terms of solar energy capture, so could serve as inspiration for future work.’

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