Bright, iridescent colors observed in nature are often caused by light interference within nanoscale periodic lattices, inspiring numerous strategies for coloration devoid of inorganic pigments. Here, we describe and characterize the septum of the Lunaria annua plant that generates large (multicentimeter), freestanding iridescent sheets, with distinctive silvery-white reflective appearance. This originates from the thin-film assembly of cellulose fibers in the cells of the septum that induce thin-film interference–like colors at the microscale, thus accounting for the structure’s overall silvery-white reflectance at the macroscale. These cells further assemble into two thin layers, resulting in a mechanically robust, iridescent septum, which is also significantly light due to its high air porosity (>70%) arising from the cells’ hollow-core structure. This combination of hierarchical structure comprising mechanical and optical function can inspire technological classes of devices and interfaces based on robust, light, and spectrally responsive natural substrates.

在自然界中观察到的明亮，虹彩颜色通常是由纳米级周期性晶格内的光干扰引起的，激发了许多无无机颜料的着色策略。在这里，我们描述和表征月球菌的隔膜产生大型（多厘米），独立彩虹色薄片的植物，具有独特的银白色反光外观。这源于隔膜细胞中纤维素纤维的薄膜组装，该薄膜纤维在微观尺度上引起薄膜干涉（如颜色），因此在宏观尺度上解释了该结构的整体银白色反射率。这些电池进一步组装成两个薄层，形成机械坚固的虹彩隔片，由于电池的空心结构产生的高空气孔隙率（> 70％），该隔片也很轻。包含机械和光学功能的层次结构的这种组合可以激发基于坚固，光和对光谱敏感的自然基板的设备和接口的技术类别。