Developmental and Structural Section
Horner, Harry , Ruchti, Tiranee , Yoon, Hana , Samain, Marie-Stephanie .
Differences in Leaf Anatomies and Crystal Macropatterns Between the Species-rich Sister Genera Peperomia and Piper (Piperaceae).
The majority of angiosperms produce calcium oxalate crystals in some or all of their plant organs, and most notably in their leaves. The crystals have different individual or aggregate shapes, and are spatially distributed within an organ. These two characters are species specific. Leaves are most amenable for study as they are plentiful and easy to process. Cleared fresh or herbarium leaves, using household bleach, ethanol and xylenes, display semi-transparent views of retained cell walls and inorganic crystals when viewed between crossed polarizers with a light microscope. Leaf crystals of Peperomia and Piper species were revealed as having distinctly different: 1) leaf anatomies; 2) crystal shapes; and 3) crystal locations or macropatterns. The 178 Peperomia species exclusively display druses throughout or concentrated over the veins in the small palisade parenchyma below a typically multilayered adaxial hypodermis, and sometimes either raphide bundles or prisms occur in the spongy parenchyma; all creating at least seven leaf crystal macropatterns. Fifty-nine species of Piper studied so far have a more complex array of crystals shapes and macropatterns that consist of: crystal sand and raphide bundles being most common, followed by prisms/styloids, sphaerites and very small 'druses', and various combinations of them. Most of these crystals occur in the palisade and spongy parenchymas sandwiched between the upper epidermis and its hypodermis and the lower epidermis and its hypodermis. Piper leaves are typically thinner than Peperomia leaves but the abundance of crystals in almost all of the species of both genera suggests a potential functional attribute associated with photosynthetic efficiency based on habitat. Finally, the observed macropatterns will be compared to published phylogenetic trees for the two genera to determine if species with the same or similar crystal macropatterns in each genus are closely associated with each other or not. These results will be further used to ascertain whether crystal shape and crystal macropatterns serve as useful taxonomic and phylogenetic characters within each genus.
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1 - Iowa State University, Genetics, Development And Cell Biology Dept, 3A Bessey Hall, AMES, IA, 50011-1020, USA
2 - Iowa State University, Undergraduate Biology Major, Ames, IA, 50011, USA
3 - Ghent University, Department of Biology, Research Group Spermatophytes, K.L Ledeganckstraat 35, Gent, 9000, Belgium
Presentation Type: Oral Paper:Papers for Sections
Location: Waterman Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 9:45 AM