Display of mitochondria in root tip cells.

A method for displaying mitochondria and proplastids in root tip sections of Tradescantia paludosa and cereals was modified from Altmann and Volkonsky. Root tips were fixed in 3% glutaraldehyde in phosphate buffer, pH 7.1, or acetate buffer, pH 4.8, for 3 hr, rinsed and postchromed overnight in 3% potassium dichromate, all at room temperature (20 C), dehydrated through a tertiary butanol series and embedded in ester wax. Four-micrometer sections were stained in hot acid fuchsin in aniline water, rinsed, treated with 1% sodium phosphomolybdate for 30 sec, rinsed and stained progressively with azure B for 3-10 min before being made permanent. Mitochondria and proplastids were stained brilliant crimson against a light blue cytoplasm with deep blue chromosomes. Previously reported difficulties with Altmann staining techniques are attributed to the erratic action of the classical fixatives used.