Abstract Detail

Developmental and Structural Section

Lee, David [1], Lakhtakia, Akhlesh [2], Strout, Gregory [3], Russell, Scott [4].

Preferential Circularly Polarized Reflection by Adaxial Epidermal Walls of Iridescent Plants.

Helicoidal cell walls, seen in off-perpendicular transverse sections under TEM, are caused by the incremental deposition of cellulose microfibrils at a constant angle, either right- or left-handed in orientation. Helicoidal structure has been observed in a variety of cell walls, but perhaps most notably in the exocuticles of beetles producing metallic iridescent colors, as well as some plants with iridescent blue leaves growing in deep understory shade of rainforests throughout the tropics. The chiral nature of these layers produces conditions for light of one circular polarization to pass through the cell wall but not of the other circular polarization in a spectral regime. In beetles, preferential reflection of one circular polarization (PRCP) has been proposed as a mechanism for iridescence and, recently, in the brilliant blue fruits of Pollia condensata C. B. Clarke [PNAS 109(2012): 15712-15715], the only publication demonstrating PRCP by a plant structure. In the Malaysian tropical rainforest understory sedge, Mapania caudata Kük, we had previously shown that the blue leaf iridescence is associated with both a helicoidal cell wall and a periodic deposition of silica nanoparticles in association with the helicoids, and have proposed that both are involved in the color production. The principal reason for a lack of data on PRCP by organisms is that the technique is most appropriate to an optical physics laboratory. Here, we report on a simple and easily replicated technique of using the preferential circularly polarized transmission by lenses of eyeglasses used in commercial 3-D cinema (Real-D®). These allow the detection of left- and right-circularly polarized (LCP and RCP) light at wavelengths in the visible spectrum, and the imaging of results to observe individual cells under a 40x dissecting microscope. Iridescent blue color reflected from the Mapaniae pidermal cells was exclusively LCP. We also observed reflected LCP light from leaf epidermises of three blue iridescent ferns: Microsorium thalindicum T. Boonkerd & Noot., M. steerei (Harr.) Ching, and Elaphoglossum metallicum Mickel. We plan additional observations, particularly of species whose wall structure has been described. Where PRCP is observed, there is a substantial difference in the observed LCP and RCP intensities, which would make this technique useful in determining the presence of helicoidal walls in non-iridescent plants.

Broader Impacts:

1 - Florida International University, Biological Sciences, Miami, FL, 33199, USA
2 - Pennsylvania State University, Department of Engineering Science and Mechanics, University Park, PA, 16802, USA
3 - University of Oklahoma, Samuel Roberts Noble Microscopy Laboratory, 770 Van Vleet Oval, Norman, OK, 73069, USA
4 - University of Oklahoma, Department of Microbiology And Plant Biology, 770 Van Vleet Oval, Norman, OK, 73019-6155, USA

Keywords:
helicoidal
cell wall
circular polarization
color
iridescence
microfibrils
epidermis.

Presentation Type: Oral Paper:Papers for Sections
Session: 15
Location: Jasperwood/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 9:30 AM
Number: 15007
Abstract ID:133
Candidate for Awards:None