Plant Photosynthesis Gets a Boost from Vibrations

Photosynthesis is a plant's life source, and by taking a closer look at its mechanics with the help of short pulses of light, scientists have found that molecule vibrations give this process an extra boost.

The findings could potentially help engineers make more efficient solar cells and energy storage systems.

Through photosynthesis, plants and some bacteria turn sunlight, water and carbon dioxide into food for themselves and oxygen for animals to breathe. It's one of the most important biochemical processes on Earth, although scientists have yet to fully understand how it works.

Researchers decided to take a closer look by extracting the photosystem II reaction centers from the leaves. Located in the chloroplasts of plant cells, photosystem II is the group of proteins and pigments that does the photosynthetic "heavy lifting." It's also the only known natural enzyme that uses solar energy to split water into hydrogen and oxygen.

Then, by using carefully timed sequences of ultrashort laser pulses, researchers were able to initiate photosynthesis and then take snapshots of the process in real time. They could view the molecular vibrations that help enable charge separation, which is the process of kicking electrons free from atoms in the initial steps of photosynthesis.

"This particular system is of great interest to people because the charge separation process happens extremely efficiently," lead author Jennifer Ogilvie said in a press release. "In artificial materials, we have lots of great light absorbers and systems that can create charge separation, but it's hard to maintain that separation long enough to extract it to do useful work. In the photosystem II reaction center, that problem is nicely solved."

Ogilvie added: "What we've found is that when the gaps in energy level are close to vibrational frequencies, you can have enhanced charge separation. It's a bit like a bucket-brigade: how much water you transport down the line of people depends on each person getting the right timing and the right motion to maximize the throughput. Our experiments have told us about the important timing and motions that are used to separate charge in the photosystem II reaction center."

The findings were published in the journal Nature Chemistry.