Structural colours in the frond of Microsorum thailandicum

Abstract

Blue and near-ultraviolet structural colours have often been reported in understorey plants living in deep shade. While this intense blue coloration is very catchy to the eye of a human observer, there are cases in which structural colours can be hidden either by the scattered light interacting with pigments or because they are found in unexpected positions in the plants. Here, we show that the fronds of Microsorum thailandicum produce structural coloration on both the adaxial and abaxial epidermal surface. While cellulose helicoidal structures are responsible for this coloration in both epidermal layers, the reflected colours are consistently different: an intense blue reflection is found in the adaxial epidermis while red-shifted and less intense colours are observed in the abaxial epidermis, possibly suggesting photo-adaptation of the plant to the light environment. By comparing the optical properties of the fern with its anatomy we computed the theoretical reflection accounting for the presence of disorder in the cellulose helicoidal architecture.

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

“…In some plants, similar layered structures can be produced by cell‐wall assembly of cellulose fibrils in an helicoidal architecture (Middleton et al, 2016). Such architectures have been observed in various organs of several distantly related plant species, including the leaves of the monocot Mapania caudata (Strout et al, 2013) and the fern Microsorum thailandicum (Steiner et al, 2018), the fruits of the eudicot Margaritaria nobilis (Vignolini et al, 2016) and the monocot Pollia condensata (Vignolini, Rudall, et al, 2012). In this architecture, microfibrils are organized parallel to each other in quasi‐planes, where adjacent planes are rotated at a slight angle with respect to one another, producing a chiral structure.…”

“…d-f, plots of modelled reflectance peak from each corresponding TEM (image above). Two sets of refractive indices were compared: n e/o = 1.586/1.524(Dumanli et al, 2014;Steiner et al,…”

Photonic paper: Multiscale assembly of reflective cellulose sheets in Lunaria annua

“…Structural color has captured the fascination of optical researchers through numerous observations throughout history, both in naturally occurring structures and in the animal world (1)(2)(3). Plants have also evolved structural colors to fulfill a variety of functions (4-7): Structurally colored leaves (8)(9)(10), flowers (11,12), and fruits (4,5,13,14) are used by plants to regulate light harvesting (8,(15)(16)(17) and attract pollinators (6,7), while they are also believed to promote seed dispersal (4,5). The few, so far, described plants whose fruits are structurally colored are understory species living in tropical regions, whose fruits reflect light spanning from deep metallic blue to green when ripe.…”

Living light : optics, ecology and design principles of natural photonic structures

“…Structural colour is more regularly observed in multicellular organisms across the plant and animal kingdoms. Here, structural colour is in detail described in plant leaves by Steiner et al [7], in primitive moth wing scales by Kilchoer et al [8], and in the blue feathers of peacocks by Freyer et al [9].…”