Optofluidics of Plants

Plants harness the interaction of light and fluids to make fuel and move water from the roots to the leaves (Source: Psaltis et al. / APL)

Plants harness the interaction of light and fluids to make fuel and move water from the roots to the leaves (Source: Psaltis et al. / APL)

If you place a house­plant next to a sunny window, you may notice the leaves bending toward the light. Plants don’t have a brain, so the vast majority of movement is controlled by the interaction of light and fluid within plant cells, says Demetri Psaltis, Dean of the School of Engi­neering and director of the Optics Laboratory at the École Poly­technique Fédérale de Lausanne in Switzer­land.

Psaltis and his colleagues have inves­tigated opto­fluidics in plants. Opto­fluidics combine optical systems, which respond to and control light, with micro­fluidic systems, which move fluids through small channels. Psaltis says he hopes to draw the attention of the optics community to plant physiology. “I was fascinated by how plants use micro­fluidics and optics to move, change color, and pump water,” Psaltis said. “We hope to provide inspiration for new ideas in optofluidic devices.”

He and his colleagues dove into the scientific literature on plants and chose five light/fluid interactions to highlight. They explored photo­synthesis, the process plants use to convert sunlight into sugar. They also examined the recent literature on the light-mediated movement of chloro­plasts, which are the tiny organelles in plants that contain the green photo­synthetic pigment chlorophyll. In addition to making fuel, plants also use light to move large amounts of water. Psaltis says he was most surprised and inspired by how plants suck water from the ground, control their tempe­rature, and keep from drying out.

“The plant actually doesn’t optimize the con­version of light to sugar,” Psaltis said. “In a tree, for example, most of the energy is used to heat and evaporate water.” The evapo­ration process draws water from the ground into the tree’s leaves, where it plays an important role in photo­synthesis. At night, when photo­synthesis shuts down, many plants conserve water by closing pores in their leaves called stomata. The stomata are another example of an opto­fluidic system. Sunlight drives a flow of ions across membranes in the stomata, which in turn causes fluid to flow into the cells and they swell open. Psaltis is now looking more closely at how membranes control fluid flow and how they might be used in opto­fluidic devices. “There’s a vast amount of literature on plant physio­logy that techno­logists could look at,” he said. (Source: AIP)

Reference: D. Psaltis et al.: Optofluidics of plants, APL Phot. 1, 020901 (2016); DOI: 10.1063/1.4947228

Link: Optics Laboratory (D. Psaltis), École Polytechnique Fédérale de Lausanne, Switzerland

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