Abstract: The present work reports microstructure-based wettability and reflectance responses of three varieties of Indian Rosaceae (Rosa) cultivars, viz. white rose (Rosa chinensis var spontanea), light pink rose (Rosa chinensis var minima) and dark pink rose (Rosa chinensis var minima). As for wettability, static and advancing and receding Contact Angles (CA) have been measured, for each type of matured rose petals. The surface roughness factors (r?), which are largely dependent on the micro-papillae assembly within the rose petal, are estimated to be, 2.74, 2.27 and 2.94 in case of White (W), Light Pink (LP) and Dark Pink (DP) petals; respectively. Moreover, the respective Contact Angle Hysteresis (CAH) values are measured as 51?, 27? and 59?. In order to exploit structural colouration through the reflectance char-acteristics, the specimens were dipped in three different media of different Refractive Indices (RI), viz. ethanol (RI = 1.36), propanol (RI = 1.39) and glycerine (RI = 1.47) for about 24 h. Upon ethanol and propanol adsorption, the LP and DP rose petals showed unusually similar reflectance patterns over a wide range of wavelengths, thus indicating a common microstructural share and structural colour contribution. The wetting-dewetting and structural colouration in natural systems, to a great extent, are dictated by the surface structure and solid-liquid and liquid-air interfaces, not only offer fundamental interest but also give scope for mimicking in artificial designs of technological interest.

Key words: microstructure, surface roughness, wettability, structural colour, reflectance