Aniline blue and fluorescence microscopy of callose in bulb scales ofAllium cepa L

Summary

• 1. The fluorescence-microscopic method is used in which substances of callose nature appear yellow when stained with water-soluble aniline blue.

• 2. Callose in sieve tubes and in other reported locations is clearly revealed, and it also appears in primary pit fields of parenchyma cells. It is especially evident in the anticlinal walls ofAllium epidermis.

• 3. The formation of callose, as judged by intensity of fluorescence, is increased by wound stimulation. Limited at first to pit fields, spreading can occur later.

• 4. Once formed, the pit callose is stable to plasmolysis, boiling water, and chemical fixation.

• 5. A major function of callose in plants is considered to be a sealing or plugging action, although there appear to be other functions.

• 6. The presence of callose in parenchymatous walls is further evidence of the close relationship between sieve fields and primary pit fields.

  This work was carried out during the winter of 1954–55 at Münster, where the first author, as a Guggenheim Fellow, was a guest of the Botanisches Institut.