Columellar Germination in Mucor Piriformis

Abstract

The first evidence of columellar germination in mucoraceous fungi is reported for Mucor piriformis isolated from fruits in California and from Chile. In one isolate, columellar ger? mination ranged from 3.6 to 10.6% in test tube cultures incubated at 21 C for 20 da, while cultures incubated for the same period at 0, 6, or 9 C did not show columellar germination. One to five hyphae originated from a single columella and formed simple or sympodially branched sporangiophores producing one to four secondary sporangia. Some columellae contained yellowish to brown protoplasmic material while others appeared empty. In 50% of these columellae, a single septum delimited the protoplasmic contents prior to germination process. In all species of Mucor, part of the sporangium is occupied by a well-defined endogenous columella (3). In Gilbertella persicaria (Eddy) Hesseltine, a close relative of Mucor, the columellae may be highly vacuolated or densely proto? plasmic; the latter condition occurs mostly in small sporangia that produce few spores (1). Such small sporangia are also produced by M. piriformis Fischer (5). In this species, most columellae are empty but some show yellowish to brownish protoplasmic contents. In some species of Mucor, the presence or absence of brownish protoplasmic contents determines the shape ofthe columella, and older columellae without such contents usually lose turgor and become pyriform (5). The columellae of the Mucorales according to Hesseltine and Ellis (3) . . are vesicles or central sterile regions continuous with the sporangiophores inside the sporangium. In contrast, Schipper (5) mentioned sprouting of sporangia and columellae in aging cultures of M. piriformis. The present study reports that columellae of M. piriformis germinate and form secondary sporangia under certain conditions of temperature and age of the cul? ture.