A Plant With Shimmering Blue Leaves!

Oct 29, 2016 By Aarathi
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We've heard of plants with green or even variegated leaves. But blue?

That's exactly what a species of begonia has. Found deep in the shade of rainforests, these hardy plants have large leaves of an unusual iridescent blue.

Research by a team from the Universities of Bristol and Essex in Britain focused on the plant's unique coloring. They found the plant has evolved to make maximum use of limited light along the undergrowth of the forests. In fact, they actually use quantum mechanics to survive. Let's find out how.

Photosynthesis 

Photosynthesis, as we know, is the process where plants convert sunlight into chemical energy. This is stored as sugars or carbohydrates in the plants. Carbohydrates provide nourishment to all living things.

But how do plants actually produce the carbohydrates? The cells of plant leaves contain structures called chloroplasts. These chloroplasts contain chlorophyll pigments which absorb the bulk of the sunlight. Only the green is reflected back, which is what we see.

Indeed, many ancestors of today's plants had purple hues, thanks to the photosynthetic chemicals they had in their leaves. By the way, chloroplasts have small tower-shaped membranes called thylakoids, which are found in random arrangements. They contain chemicals that are sensitive to light. In other words, when light passes through these thylakoids, it triggers production of the all-important chemical energy.

The Secret Of The Blue Leaves

Begonias are popular indoor flowering plants since they can survive without direct sunlight. That's because they come from the rainforest, where very little sunlight gets through the dense foliage. So, these plants have evolved to make the best use of whatever access to light they get.

Many species of begonia have a blue sheen to their leaves, but the Begonia pavonina or peacock begonia has fully cobalt leaves with a vivid shimmer. Curiously, scientists noticed that the blue shimmer was stronger under low light conditions, and tended to fade under bright light.

Since the Malaysian plant is quite delicate outside its natural environment, scientists worked with a sturdier hybrid that still retained its blue leaves. With an electron microscope, they studied its chloroplasts better known as iridoplasts due to their vivid coloring. The iridoplasts contained thylakoids arranged in distinct layers, quite unlike the normal. They were surprised to find that all these layers tended to reflect away blue light waves, which gave the leaves that color.

The main discovery was that these layers of thylakoid membranes behaved like a crystal and actually 'bent' the waves of light which passed through them. This process of disturbing the flow of light waves is called 'interference' in quantum mechanics. The bending gave even the reflected blue light a shimmer. Additionally, since the remaining light waves actually slow down as they are being bent, the plant has an even better chance of absorbing more light than before. They are more energy efficient because of this.

Clearly, the iridoplasts were far better than ordinary chloroplasts in carrying out photosynthesis under low-light conditions.  Perhaps, even green plants could be manipulating light in their own way too. Scientists are curious as to what other evolutionary tricks and secrets are still undiscovered in plants.