About 75% of flowering plants produce calcium oxalate crystals in some or all
of their organs. Because these crystals occur in various shapes and hydration
states that are specific and consistent within each organ, they have been used
periodically as an internal taxonomic character. Since crystals and their macropatterns
are usually retained in the mature leaves and stems even after they die or drop
off the plant, such information should be useful for identification purposes,
possibly in forensics. Only a few studies have followed the development of the
crystals into what is called a macropattern in a mature organ such as a leaf.
Such a study can aid our understanding of how different crystals form and how
they relate to their specific organ tissues. Shown here are large, prismatic
crystals in cleared mesophyll cells of a pomegranate leaf, observed between
crossed polarizers. The prismatic crystal nearest the center of the image has
a central, nonpolarizing core, and two of the crystals display epitactic or
Botanical Society of America
copyright: Harry T. Horner, BSA
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