Bleached Tissue Research Articles

Rapid bleach for melanin.

Complete bleaching of melanin in strongly pigmented specimens embedded in paraffin or polystyrene, and sectioned and mounted on slides, is possible in 1-3 hr at 37 C in a solution of 20 ml of benzyl alcohol, 10 ml of acetone, 5 ml of 10% hydrogen peroxide and 4 drops of a 25% ammonia solution. The bleached tissues are well preserved and tolerate further histochemical treatments. All the stains and reactions tested give results identical to or better than those obtained after 24-48 hr oxidation in 10% hydrogen peroxide.

Inhibition of chlorophyll synthesis in Lemna minor by nalidixic acid

Nalidixic acid bleached Lemna minor during growth in white light on a medium supporting heterotrophic growth. Immature, vacuolate mesophyll cells from bleached tissue contained plastids with aberrant thylakoids and had less-electron-dense cytoplasm than normal cells. Mitochondrial shape appeared normal. Individual bleached plants regreened and regained normal rates of growth after transfer to nalidixic-acid- (NAL-) free medium. Frond multiplication was also inhibited by NAL during growth in darkness. Purine and pyrimidine ribonucleosides did not prevent NAL-induced bleaching or growth inhibition.

Control of Senescence in Marchantia by Phytochrome

Mature green tissue of Marchantia polymorpha L. bleaches markedly when placed in continuous darkness for 4 days but remains green when given daily 1-hour photoperiods of white light. The tissue, however, is induced to bleach when each daily 1-hour photoperiod is terminated with a brief irradiation with far red light. The bleaching does not occur when each irradiation with far red light is followed by a brief irradiation with red light. The bleaching is taken as an index of senescence since the loss of chlorophyll in the bleached tissue is accompanied by a breakdown of cell organelles and cytoplasm. Phytochrome is clearly implicated in the control of senescence by light. It was also found that 5 minutes of red light given once a day was as effective as the 1-hour photoperiods with white light in preventing the bleaching and that bleaching was induced when each daily 5-minute irradiation with red light was followed by a 10-minute irradiation with far red light.

Evaluation of the Effects of Eleven Bleaching Agents on Ground Cocoa Bean Tissue, Insect Fragments, and Rodent Hairs

Abstract Eleven bleaching agents were used to decolorize cocoa tissues, and their effects on insect fragments and rodent hairs were studied. Gilorine bleaches, potassium permanganate, and hydrogen peroxide all result in good bleaching of ground cocoa. However, chlorine bleaches completely destroy rodent hair, and potassium permanganate is not effective for high fat products. Hydrogen peroxide decolorizes cocoa bean tissue very well and does not destroy rodent hairs nor decolorize insect fragments. A mechanical means of evaluating the amount of bleaching of cocoa bean tissues is also described. Future studies are planned on the use of hydrogen peroxide as a plant tissue bleaching agent