Plants are active organisms down to the cells. The chloroplasts (the organelles that convert light into energy) in some plants begin to move around within seconds of being exposed to light, and regroup into flat layers when the light dims.
“They have this mesmerizing and wonderful building behavior,” says Nico Schrama, a physicist at the University of Amsterdam. In a new study, he and his colleagues found that chloroplasts actually become a kind of “glass” when pressed against their cell walls in the dark. The findings help explain how chloroplasts alternate between rigid solids and flowing liquids to best absorb the sun.
For physicists, glasses are a broad category of solids. Hard candies can be glass. It’s the same with plastics, even spreadable mayonnaise, to a certain extent. Crystalline structures, such as ice, are solids because the particles are arranged in an orderly fashion, while the disordered particles of liquids turn into glass when packed so tightly that they hardly move.
Schramma’s team found that chloroplasts can undergo similar processes.Physicists tracked chloroplasts in aquatic plants Elodea Densa We built a model of their motion under different lighting conditions and quickly recognized features of the glassy system in the data. The recently published results are Proceedings of the National Academy of Sciences united states of americaindicating that individual chloroplasts cluster and trap each other instead of slowing down in low light.
The finding is “very compelling evidence of a glass transition,” says Syracuse University biophysicist Lisa Manning. Recognizing this process will allow physicists to study the complex dynamics of chloroplasts as a familiar type of system, the researchers say.
The results also reveal hidden similarities to other glass-like living systems. These glass transitions serve an important purpose of flexibility. For example, the developing embryo moves between fluid and rigid bodies. And hard tumors spread throughout the body by behaving like liquids.
In little light, the glassy state of chloroplasts forms flat layers to absorb as much light as possible, like a cat in a patch of sun. In high light conditions, chloroplasts weave and fend off exposure to a minimum. “It’s easy to think that it’s not static, but at the cellular level, it’s as dynamic as any other organism.”
Hungerter asks whether to study at E. Dense It can be generalized to other plants with different chloroplast shapes, sizes and movements. The authors plan to work with molecular biologists in future studies to integrate that level of biological detail into physics-inspired models.
