Developmental and Structural Section
Lersten, Nels R. , Horner, Harry T. .
Leaf Calcium Oxalate Duplex and Concretion Idioblasts: Unique Features in Tribe Naucleeae (Rubiaceae).
The seven recognized calcium oxalate crystal forms in plants (aciculars, crystal sand, druses, prisms, raphides, sphaerites and styloids) occur in various members of Rubiaceae, the fourth largest angiosperm family (611 genera and 13,148 species). The mostly African and Asian Tribe Naucleeae (179 species and 24 genera), in addition, exhibits one rare and one undescribed crystal form. Leaf samples from herbarium specimens (103 species [59%] from 23 genera [96%] of total) obtained from Iowa State University, Field Museum and Missouri Botanical Garden were cleared and viewed light microscopically between crossed polarizers. Prominent crystal-containing idioblasts occur in every genus, and are selectively located in: 1) a conspicuous file just above at least the smaller veins; 2) scattered above or alongside veins; or 3) in spongy mesophyll where idioblasts often form a reticulate mesh. No conspicuous idioblasts occur in leaf palisade mesophyll or epidermis. Most idioblasts contain crystal sand, and the majority (55%) displays a conspicuous embedded imperfect or complete druse; in four species some idioblasts had two to four embedded druses in the crystal sand. These ‘duplex’ idioblasts containing crystal sand and druses are newly described here. In some idioblasts a single druse is most prominent, with scanty crystal sand surrounding it, and in eight species druses occur alone. The factor(s) affecting these variations from sand-only to druse-only idioblasts is/are not known. In one genus, large idioblasts above veins have crystal sand-like contents condensed into a solid crystalline ‘concretion’, a second newly described crystalline form. Besides the large duplex and concretion idioblasts, tiny individual ‘secondary’ crystals (prisms, druses, raphides, aciculars, sphaerites) also occur variously in some normal-appearing mesophyll and epidermal cells in 60% of the taxa studied. These different crystal forms with their special locations in leaves (crystal macropatterns) is species- and genus-specific, and potentially may be of systematic value within the Tribe Naucleeae and the Family Rubiaceae.
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1 - Iowa State University, Ecology, Evolution and Organismal Biology, 253 Bessey Hall, Ames, IA, 50011, USA
2 - Iowa State University, Genetics, Development and Cell Biology & Microscopy and NanoImaging Facility, Ames, IA, 50011-1020, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Wednesday, August 4th, 2010
Time: 9:00 AM