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Abstract Detail

Developmental and Structural Section


Looking through the windows of the window Peperomias: a crystal-clear view.

The window-leaved Peperomia clade (Piperales) is a monophyletic group among the first branching exclusively terrestrial clades in the genus. Very few of these species have been studied so essentially nothing is known about their internal leaf crystal configuration. All species occur in seasonally dry forest regions in northern Peru (with a few localities in S Ecuador), which is an extremely dry habitat for about 8-9 months a year. At the end of the rainy season plants are bright green and very succulent (primarily due to prominent ‘window’ hypodermal tissue), and at the end of the dry season, they are pale green and the leaves may even be shriveled. Other common plants in their habitat, such as cacti, have necessary prominent water-containing tissue like that of the window leaves. The elevation range of the plants ranges between 500 and 3000 m above sea level, and they all share the same habitat, where it is hot and dry during most of the year, and solar radiation is very high.  Thirty-five window Peperomia species, studied from the Ghent University Botanical Garden living collection, were chemically cleared or fixed for paraffin sectioning and scanning electron microscopy.  Leaves range from being adaxially flexed exposing the window tissue, partially closed or completely closed where the abaxial epidermis serves as the outer exposed surface of the leaf.  The massive central window tissue is internally subtended by the small-celled palisade parenchyma, several layers of spongy mesophyll containing the vasculature and a single-layered abaxial epidermis.  Location, leaf shape, and types of calcium oxalate crystals are specific to each species.  Some inner most hypodermal cells next to the palisade parenchyma and abaxial epidermis have highly refractive cell walls.  Crystals of varying shapes (druses, crystal sand, prisms/styloids) are prevalent in both the window tissue and spongy mesophyll of some species, and druses only occur in the palisade parenchyma.  Crystal sand and styloids do not exist in any of the 86 non-window, tropical species that we have studied, to date, and they never occur in the hypodermis. This represents a significant deviation of crystal shape and macropattern that only occurs in the sister genus Piper and some other members of the Piperales. These results, when placed in a phylogenetic context and compared to geographical location and elevation, elicit novel hypotheses about the importance of the leaf anatomy, crystal shape and location, and crystal evolution when compared to other members of the Piperales.

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1 - Iowa State University, Genetics, Development And Cell Biology Dept, 3A Bessey Hall, AMES, IA, 50011-1020, USA
2 - Centro Regional del Bajío, Instituto de Ecología, Avenida Lázaro Cárdenas 253, Pátzcuaro, Michoacán, 61600, Mexico
3 - TU Dresden, Dept. Of Biology, Institut Of Botany, Zellescher Weg 20b, Dresden, N/A, 01062, Germany

leaf macropattern
window Peperomias.

Presentation Type: Oral Paper:Papers for Sections
Session: 20
Location: Pines North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 8:45 AM
Number: 20003
Abstract ID:120
Candidate for Awards:None

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