Webb, Mary Alice .
Calcium Biominerals in Trichomes of the Brassicaceae.
Higher plants contain a variety of biomineral deposits, including calcium oxalate, calcium carbonate, and silica, and the composition and location of these deposits usually follows taxonomic lines. Biominerals have not previously been identified in the Brassicaceae. Energy-dispersive x-ray analysis of epidermal cells in selected plants of the Brassicaceae consistently revealed that trichomes contained elevated calcium in comparison to pavement cells. SEM observations combined with elemental analysis revealed that calcium-rich mineral deposits were concentrated within the trichome wall. In the light microscope under crossed polarizers, walls appeared highly birefringent, and this birefringence was reduced following acid extraction of mineral. The nature of this mineral was investigated in Erisymum spp. and Arabidopsis thaliana. Upon treatment with acetic acid, mineralized layers in Erisymum trichomes dissolved with effervescence, indicating the presence of calcium carbonate. Preliminary analyses with FTIR supported the existence of calcium carbonate and indicated that calcium oxalate might also be present. Round protrusions observed on trichome surfaces did not dissolve in xylene, indicating they were not a feature of the cuticle. However, sequential treatment with xylene and acetic acid resulted in collapse of the trichomes and dissolution of surface protrusions, suggesting that calcium carbonate deposits served to reinforce cell wall structure and formed the surface protrusions as well. In Arabidopsis trichomes both calcium and phosphate were elevated in comparison to pavement cells. Analyses in progress indicate that trichome walls may contain calcium phosphate, as well as calcium carbonate. Some known mutants in cell wall components also show alterations in the structure of surface protrusions on trichomes, indicating that the wall might serve as a matrix for mineral deposition.
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1 - Purdue University, Botany and Plant Pathology, Whistler Research Building, West Lafayette, IN, 47907, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM