Vibrations Enhance Efficiency of Photosynthesis in Plant Leaves

Scientists are taking a closer look at photosynthesis with the help of short pulses of light and now, they've found out how vibrations can actually enhance the efficiency of this process. The findings could help engineers potentially make more efficient solar cells and energy storage systems.

Photosynthesis allows plants and some bacteria to turn sunlight, water and carbon dioxide into energy for themselves in addition to oxygen for animals to breathe. It's one of the most important biochemical processes on Earth, though researchers still don't fully understand how it works.

That's why researchers decided to take a closer look. The scientists extracted what's called the photosystem II reaction centers from leaves. Photosystem II is located in the chloroplasts of plant cells and is a group of proteins and pigments that does the "heavy lifting" when it comes to photosynthesis. It's also the only known natural enzyme that uses solar energy to split water into hydrogen and oxygen.

After extracting photosystem II reaction centers, the researchers then used carefully timed sequences of ultrashort laser pulses in order to match the speed of the reactions taking place. These laser pulses allowed them to take snapshots of the process in real time.

"This particular system is of great interest to people because the charge separation process happens extremely efficiently," said Jennifer Ogilvie, one of the researchers, in a news 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."

So what did the scientists find? It turns out that specific vibrational motions occurred during charge separation.

"What we've found is that when the gaps in energy level are close to vibrational frequencies, you can have enhanced charge separation," said Ogilvie. "It's a bit like a bucket-bridgade: 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 thoroughput. Our experiments have told us about the important timing and motions that are used to separate the charge in the photosystem II reaction center."

The findings are published in the journal Nature Chemistry.