Optimal Glassy Packing of Chloroplasts in Plant Cells

Photosynthesis is essential for life on Earth, and plants have evolved various mechanisms to optimize it under changing light conditions, including cellular adaptations through chloroplast movement. A light-controlled, actin-binding mechanism enables chloroplasts to move toward or away from light based on intensity, allowing them to self-organize into light-adapted configurations. In this study, we explore chloroplast rearrangements in Elodea densa, finding a state near a glass transition when chloroplasts form a single layer to boost light absorption. We also examine their optimal packing and show how this self-organization helps chloroplasts respond to strong light, presenting chloroplast movement as an in-vivo model for active matter in confined spaces.