Using structural colour to track length scale of cell‐wall layers in developing <i>Pollia japonica</i> fruits

Helicoidally arranged layers of cellulose microfibrils in plant cell walls can produce strong and vivid coloration a wide range species. Despite its significance, the morphogenesis walls, whether reflective or not, is not fully understood. Here we show that by optically monitoring reflectance Pollia japonica fruits during development directly map structural changes wall on scale tens nanometres. Visible-light spectra from individual living cells were measured throughout fruit maturation process compared with numerical models. Our analysis reveals periodic spacing helicoidal architecture remains unchanged development, suggesting interactions cell-wall polysaccharides lead to fixed twisting angle helicoids wall. By contrast conventional electron microscopy, which requires different specimens at stages noninvasive optical technique present allowed us monitor live biological photonic systems as they develop. This method therefore applicable investigations tissues other organisms.