Bulk Specimen Preparation For X-Ray Microanalysis of Plant Cells
Numerous plant pathological investigations have been published where pathologists determined elemental differences between diseased and healthy plant tissue using unfractured bulk specimens and energy dispersive x-ray microanalysis (EDX). In these studies effects of specimen preparation procedures were largely ignored (1). Our objective was to compare bulk specimen preparation procedures using healthy leaf epidermal (surface) cells of barley, Hordeum vulgare, (Fig. 1) to determine advantages and disadvantages of each procedure for reference to future pathological work using EDX. Three preparation procedures were compared: 1) Frozen-hydrated (FH) specimens to maintain soluble and insoluble elements in situ; 2) Freeze-dried (FD) specimens to maintain total soluble and insoluble elements and allow deeper beam penetration than does FH, and; 3) Formalin/acetic acid/ethanol (FAA) fixed specimens, dehydrated in ethanol, and critical point dried (CD) using CO2, for determination of elemental loss in liquid fixatives (2,3).Aluminum specimen stubs were colloidal graphite coated (leaf segments attached to graphite areas) leaving clean Al margins for calibration.