Biologists have developed a powerful new tool for controlling plants using pulsed light.

Plants have microscopic small pores on the leaf surface, stomata. With their help, they regulate the flow of carbon dioxide for photosynthesis. They also use stomata to prevent too much water loss and wilting during drought.

The stomatal pores are surrounded by two guard cells. If the internal pressure of these cells drops, they relax and close the pores. When the pressure rises, the cells move apart and the pores expand.

Thus, stomatal movements are regulated by guard cells. The signaling pathways in these cells are so complex that people find it difficult to directly interfere with them. However, researchers at the Julius Maximilian University (JMU) of Würzburg in Bavaria, Germany have nevertheless found a way to control stomatal movements remotely – using pulses of light.

Researchers have inserted a light-sensitive switch into the guard cells of tobacco plants. This technology has been borrowed from optogenetics. It has been used successfully in animal cells, but its use in plant cells is still in its infancy.

The scientists used a light-sensitive protein from Guillardia theta algae as a light switch – namely the anionic channel ACR1 from the channel rhodopsin group. In response to the light pulses, the switch ensures that chloride flows out of the closing cells and potassium is supplied. The protective cells lose their internal pressure, relax, and the pores close within 15 minutes. “The light pulse is like a remote control of stomatal movement,” the study authors note.

Exposure to light almost completely prevented the transpiration of the plants.