How Plants Photosynthesize in Fluctuating Light

For plants, the process of photosynthesis is key for their survival. But living in a world where light is constantly fluctuating, shaded by clouds and overhanging trees one minute and basking in the Sun's rays the next, they had to learn to efficiently harvest the light's energy. Now, new research shows just exactly how plants do it.

The answer lies in a protein called KEA3, which researchers have realized is crucial for switching photosynthetic efficiency on a dime in changing light conditions.

"Our discovery of this built-in machinery for responding to light conditions makes KEA3 a new target for those interested in improving crop productivity, as well as for advancing basic knowledge of photosynthetic biochemistry," study co-author Martin Jonikas said in a press release.

Photosynthesis is the process by which plants convert energy from sunlight into chemical energy in the form of sugars. These sugars are not only used by plants to grow and function, but also provide food for humans and animals that eat them. This cycle takes place in two stages. First, plants absorb light in the form of photons and use it to produce energy storage molecules. In the second stage, these molecules allow carbon from the air to be converted into sugars like sucrose and starch.

In order to maximize energy capture during photosynthesis while also preventing excess energy from causing damage, plants have learned to rely on KEA3.

As described in the journal Nature Communications, under full sunlight, the energy from excess absorbed photons is intentionally released by a plant as heat. However, if a plants is shaded, it must immediately switch from this mechanism to one that allows it to stock up on as many photons as possible, not knowing when to expect light to show up again.

Led by Jonikas and Ute Armbruster from Carnegie University, a team of researchers used advanced analytical techniques to determine that KEA3 is what allows plants to accelerate the switch from its full sunlight mode to its shade-adapted mode. This rapid response to light intensity makes plants more efficient in their energy conversion during the first stage of photosynthesis.

This research tells scientists more about plants and how they have adapted their biology to the world's changing environment, as well as provides practical implications for improving agricultural productivity.