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  • Author or Editor: Gary R. Hooper x
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Abstract

A technique was developed which permits observations of a single rose petal segment through the stero-light microscope (SLM), scanning electron microscope (SEM), transmission electron microscope (TEM), and light microscope (LM). The procedure consisted of viewing the fresh tissue with SLM, fixing and post-fixing in glutaraldehyde and osmium, respectively, and dehydrating in ethanol. The alcohol in the tissue was subsequently replaced with increasing concentrations of iso-amyl acetate, the tissue critical point dried, coated with C, and viewed in the SEM. The tissue was removed from the SEM mounting stub, pressure embedded in epoxy resin at 28 kg/sq cm (400 psi), polymerized, sectioned, stained, and viewed with both the TEM and LM. The technique of pressure embedding samples in epoxy resin eliminated the problem of rehydration and subsequent dehydration of tissue following SEM observation. Furthermore, this new technique reduced the time required for observation with multiple microscopic optical systems, while still offering latitude in the time between the various steps which has been a drawback in previous techniques.

Open Access

Abstract

UHF Electromagnetic energy (2450 MHz) is lethal at dosages from 100-200 J/cm2 to seeds of several weed species. Seeds were exposed to uniform energies by placing them in a quartz tube and inserting the tube in a waveguide. Seeds of barnyard grass, (Echinochlea crusgalli (L.) Beauv.), large crabgrass (Digitaria sauginalis (L.) and common purslane (Portulaca oleracea L.) showed no visible external damage when viewed in the scanning electron microscope at up to 5,000 × after treatment. No discernible internal damage was visible when tissues were immediately fixed and viewed by transmission electron microscopy after receiving minimum lethal dosages of UHF energy. At higher UHF dosages, membrane breakage and loss of integrity of organelles was observed. ATPase activity in treated seeds was monitored by transmission electron microscopy as an indicator of possible UHF destruction of enzymes. ATPase activity of tissues was absent after minimal or higher dosages of microwaves. Cells receiving minimal UHF treatment otherwise appeared normal. Toxicity from microwaves may occur as a result of selective heating of cells which results in partial protein denaturization and inactivation of key enzymes.

Open Access