Developmental and Structural Section
Filonenko, Andrew .
Fruit structure and pericarp anatomy of ash species (Fraxinus L., Oleaceae).
As part of comparative carpological research of Oleaceae family we anatomized fruits of more than 40 Fraxinus species.
Fraxinus fruits develop from upper dimerous syncarpous gynaeceum. Each locule contains a single ovule; only one ovule usually develops. Ripe fruit is dry, thickened in base and flattened in distal zone that becomes a terminal symmetrical wing. On the cross section fruits are often elliptical (F. ornus L. is roundish).
The pericarp of all Fraxinus species we studied is clearly differentiated into three histogenetic zones: exocarp, mesocarp, and endocarp (developing correspondingly from outer epidermis, mesophyll, and inner epidermis of the carpel). Exocarp of all taxa we studied is represented by a monocellular epidermis. The epidermis usually consists of flattened cells, rarely of cubical cells (F. pennsylvanica Marshall, F. tomentosa Michx.). Most exocarp cells are thin-walled. Peltate trichomes are frequently found on the fruitís surface. Exocarp is covered with thick smooth cuticle. Mesocarp of Fraxinus species is differentiated into two zones. Parenchymal cells (often compressed radially) form the outer mesocarp zone. Isolated phlobaphene-containing cells and very rare individual sclereids (F. angustifolia Vahl, F. mandshurica Rupr.) and parenchymal cells containing crystals (F. zanthoxyloides Wall. ex DC.) can be found. Quite often some intercellular spaces develop in the mesocarpís parenchyma (F. velutina Torr., F. biltmoreana Beadle). Inner mesocarp zone is composed of large sclereids put in rows, usually polygonal, with heavily incrassated lignificated walls. Endocarp is represented by an often intermittent layer of thin-walled cubical cells.
We uncovered a common fruit structure and pericarp anatomy across all 40 species included in our study. This confirms a monophyly of the genus Fraxinus. We described a morphogenetic fruit type of Fraxinus as an upper syncarpous dry winged one-seeded pyrenarium.
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1 - Main Botanical Garden of Russian Academy of Science, Department of dendrology, Botanicheskaya ul., 4, Moscow, 127276, Russia
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM