Abstract
Deposition of wax on the surface of johnsongrass occurs through two means: A. secretion through the cuticle of epidermal cells, resulting in an amorphous base layer and, then, as deposition continues, in flaky wax crystals; and B. wax filaments on the leaf surface produced by silica cell-cork cell associations . The latter process results in smooth overlay wax whose effects are seen as the glossy surface of the mature leaf. The sequence of initial wax deposition resulting in the formation of wax crystals, but not wax filaments can be duplicated in vitro. The purpose of this study is to delineate internal and external structures in cork cells that may be involved in wax filament production.Greenhouse-grown johnsongrass leaves of varying ages were used in this study. For SEM, leaf tissue was air-dried (AD) in a desiccator (for optimum wax preservation) or critical point dried (CPD). Leaf tissue for CPD was fixed overnight in 5% glutaraldehyde in 0.1M cacodylate acid pH 7.0, dehydrated in ethanol, then dried in a Balzers CPD 020 critical point drier. Some tissue was dewaxed by dipping in chloroform for 1 min before immersion in fixative, then further washed in chloroform overnight on a rotator at the end of the dehydration series. After coating with 10 nm of AuPd, the specimens were viewed in a JEOL JSM 840 scanning electron microscope. Material for TEM was fixed in 3% w/v glutaraldehyde, post-fixed in 1% w/v OsO4, then dehydrated and embedded in Spurr’s Medium. Thin sections were observed in a Zeiss EM1OCR transmission electron microscope.
Published Version
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