Blue begonias use quantum mechanics to survive on forest floor

25 Oct 2016

Iridescent begonia. Image: University of Bristol

The mystery behind why some begonia plants have a blue sheen on their leaves has been uncovered, as the result of quantum mechanics and photonics to survive the darkness of the forest floor.

You don’t usually hear quantum mechanics when discussing the intrinsic patterns on the leaf of a plant, but research from the University of Essex has managed to link the two.

The research team, led by Dr Heather Whitney, was trying to figure out why a sheen on the leaves of some begonias – a common household and garden plant – would appear blue.

Harnessing light at the nanoscale

While 1,500 species of begonia are known to exist, only a few were found to have a blue sheen – with suggestions that it might be used to deter predators or protect the leaf from too much light.

As it turns out, the latter couldn’t have been further from the truth.

By placing the affected begonia species in near dark conditions, the sheen was at its strongest; but when it was placed in bright light, the sheen slowly retreated.

This led the team to analyse the structure of the leaves, and it was astonished to find that it has evolved its individual chloroplasts to act almost like reflective mirrors, with just a few hundred nanometres in thickness.

To make things even weirder, the plant appears to follow the peculiar actions of quantum mechanics, with light actually slowing down as it passes through the begonias’ chloroplasts.

Referred to as ‘slow light’, the quantum effect is the result of the crystal-like tower structures called thylakoids found in the chloroplasts. It is then combined with an uptake in red-green light to boost photosynthesis by 10pc in dark conditions.

Might be more common than we think

The researchers were amazed to find that these structures looked almost identical to photonic structures used to make miniature lasers in labs, and with this, the begonias are able to harness more light to survive the darker forest floors.

Speaking to Popular Mechanics, Whitney said of the discovery: “It’s just wonderful and logical to think that a plant has evolved an ability to physically manipulate the lighting around it in a variety of different ways.

“I think it really raises the prospect that this type of phenomenon might even be more widespread than we realise in the plant kingdom. Perhaps we just don’t notice other plants that are doing this because they don’t have a strange colour.”

The team’s research has now been published in Nature Plants.

Colm Gorey was a senior journalist with Silicon Republic