GoKawiilLiving on light is a dangerous game. Not only do the sun’s rays carry ultraviolet waves that can snap DNA strands and degrade molecules, but they also vary wildly in intensity. Plants must endure and thrive through soft morning light and blazing summer afternoons, through shade one moment and full sun the next. Their solar calories come in a trickle — or a deluge.
“Think of a cloud obscuring the sun, and suddenly the cloud passes and the sun ray hits a leaf,” said Nico Schramma, a biophysicist at Amsterdam University Medical Center. “Something has to change because the intensity might change a hundredfold.”
Plants aren’t passive. They respond accordingly. They can reorient themselves by rotating their leaves and stems to seek sunbeams or shade, but this mechanism works on a scale of minutes or hours. For finer responses, their cells must mobilize as well. Within every plant cell are chloroplasts, disc-shaped organelles that turn sunlight into sugars. And while plants have to remain mostly stationary, chloroplasts do not.
“Chloroplasts move,” Schramma said. He likened their behavior to that of a flock of sheep seeking shade on a bright day: Intense light similarly shepherds chloroplasts into shaded patches along the cell wall.
“Light is the best friend and worst enemy of chloroplasts,” said Mazi Jalaal, a biophysicist at the University of Amsterdam who supervised Schramma’s doctoral work. “They need it for photosynthesis. But the moment the light intensity goes too high, they have to run away from it.”
Recently, Schramma and Jalaal have obsessed over a mystery of chloroplast physics. How does each organelle balance the plant’s appetite for light with its distaste for too much? And how, in turn, is this expressed as patterns within a cell? In fall 2025 in the Proceedings of the National Academy of Sciences, they reported that the chloroplasts in Elodea, a common aquarium waterweed that they use as a model plant, self-organize into a sort of mathematical optimum. They pack their cell’s surface densely enough to absorb ample light while populating the cell sparsely enough to meander and hide efficiently when they need to.
The biophysicist Nico Schramma recently solved a math problem tucked into a plant cell: Do sunlight-harvesting organelles pack optimally? Courtesy of Nico Schramma
“The beautiful thing we see here is what a great designer evolution is,” said Dakota McCoy, an evolutionary biologist studying photosynthesis at the University of Chicago. “When you see something fit your simulation really, really well, like this paper does … is it a coincidence, or is it that it evolved to be that way?”
Natural Math
Jalaal’s path to this field sounds like a punch line. His mother taught high school biology. His father, high school physics. The family debated which direction the teenager would go in his career. Voilà, biophysics.
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