July 2020
Vol 6, Issue 27

About The Cover

Cover image expansion

ONLINE COVER In the natural world, bright, iridescent colors may be caused by light interacting with tiny periodic lattices rather than inorganic pigments. However, scientists had not yet documented silvery-white, thin, lightweight colored structures in plants. Giulia Guidetti and colleagues characterized the anatomy and optical properties of Lunaria annua, a flowering plant native to the Balkans and southwest Asia and commonly known as "silver dollar," or "money plant." The researchers found that the plant's silvery, luminous appearance results from its ordered cell structure–cellulose fibers in its septum cells are organized in two thin layers, giving the septum an iridescent appearance. Since the plant's white photonic pods can be cultivated, Guidetti et al. suggest it may be possible to "grow" photonic structures that could be used in cosmetics and anti-counterfeiting devices. The septum's structure may also provide botanical inspiration for fabricating large-scale, lightweight photonic reflectors. [CREDIT: SILKLAB, TUFTS UNIVERSITY]