Developmental and Structural Section
Horner, Harry , Wanke, Stefan , Samain, Marie-Stéphanie .
The world's smallest bio-inspired light reflectors: are the internal leaf crystals important to species of Peperomia and Piper (Piperaceae) growing in low-light-intensity environments?
Inorganic crystals formed by plant cells are common in about 75% of the flowering plants, most gymnosperms, many ferns and some green algae. These crystals, though common,have eluded biologists for centuries in being able to identify their functional significance. Even though a number of possible functions have been suggested in the literature, none of them have proven to be universally tested or accepted. The species-rich sister genera Peperomia and Piper often share similar geographic ranges. They each have leaves with different anatomies and thicknesses, however, their photosynthetic tissues have a common feature of containing distinctly arranged crystals of different shapes identified as macropatterns. The178 Peperomia species studied consistently have druses associated with the common single-layered palisade parenchyma and sometimes with underlying raphides and prisms, whereas the 59 Piper species studied typically have crystal sand, a combination of crystal sand and styloids or raphides in their multilayered chlorenchyma. Categorizing these different types of crystals and their macropatterns by genus shows phylogenetic relationships that indicate increasing complexity of the crystal macropatterns. These results can be used as characters for taxonomically identifying species. Regardless of the crystal type associated with the chlorenchymatous tissues in species of either genus, the crystals occur in the central vacuole of these cells and they are surrounded by many chloroplasts. In Peperomia these plastids may contain thylakoids with massive grana stacks oriented perpendicular to the druse. In studying vibratome-sectioned leaves of three species of Piper, the crystal sand crystals in the vacuoles actively tumble when exposed to a microscopic beam of white light. This latter movement has been captured using near real-time, time-lapse microcinematography. The mechanism for this movement is not known at the present time. Peperomia druses do not move when exposed to directional light but may be affected by the intensity of light perpendicular to the leaf lamina as they appear in different locations of the elongated vacuoles in preserved sections. Depending on the species, the druses range in diameter from about 3 to 36ĆˇĀ¼ min diameter. These spherical, multifaceted druses are the subject of planned research to reproduce them in vitro with nano-range diameters, and substitute cations and anions to produce durable crystal nano-homologs to include in solar cells for increasing light harvesting efficiency.
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1 - Iowa State University, Genetics, Development And Cell Biology Dept, 3A Bessey Hall, AMES, IA, 50011-1020, USA
2 - Technische Universität Dresden, Institut für Botanik, Dresden, 01062, Germany
3 - Ghent University, Department of Biology, Research Group Spermatophytes, K.L Ledeganckstraat 35, Gent, 9000, Belgium
Presentation Type: Oral Paper:Papers for Sections
Location: Union D/Hyatt
Date: Tuesday, July 10th, 2012
Time: 4:00 PM