Optical structure and function of the white filamentary hair covering the edelweiss bracts

TL;DR

This study investigates the optical properties and nanostructure of edelweiss bracts, revealing a photonic structure in the hair layer that absorbs ultraviolet radiation, contributing to the plant's UV protection.

Contribution

It uncovers a unique photonic nanostructure in edelweiss hair filaments and models their role in UV absorption, linking structure to function in plant optics.

Findings

Hair layer exhibits a photonic crystal structure.

Layer absorbs near-ultraviolet radiation.

Photonic model explains UV absorption mechanism.

Abstract

The optical properties of the inflorescence of the high-altitude ''Leontopodium nivale'' subsp. ''alpinum'' (edelweiss) is investigated, in relation with its submicrometer structure, as determined by scanning electron microscopy. The filaments forming the hair layer have been found to exhibit an internal structure which may be one of the few examples of a photonic structure found in a plant. Measurements of light transmission through a self-supported layer of hair pads taken from the bracts supports the idea that the wooly layer covering the plant absorbs near-ultraviolet radiation before it reaches the cellular tissue. Calculations based on a photonic-crystal model provides insight on the way radiation can be absorbed by the filamentary threads.