Regeneration on Phycomyces sporangiophores. I. Induction by decapitation and basal cutting on sporangiophores attached to mycelium and after isolation

Abstract

Phycomyces blakesleeanus sporangiophores attached to mycelium and isolated sporangiophores cultured on plain agar blocks were decapitated at 1–2 mm below the apex (stage 1) or the top of the sporangium (stages 3, 4). One or more sporangiophore initials regenerated at or very near the wound closure after formation of a cross wall. They emerged only from the side on 82–85% of all parents and on most of the rest from the wound closure wall. Lateral initials frequently perforated the original wall. Regeneration on isolated and attached sporangiophores reached 100% at 12 h on stage 1 and 18 h on stage 3, but only 80% after 24 h on stage 4. The frequency of two or more initials per parent decreased from stage 1 to 4 and was greater on attached than on isolated specimens. Fewer than half of all parents with two initials showed maturation of both. Single sporangiophores elongating on isolated stage 1 parents had a larger diameter, greater stage 1 length, and 66% greater final length than on stage 4. Stage 1 was always very short (average maximum, 5.1 mm). Sporangium formation and maturation were most synchronized after regeneration on stage 1 and least on stage 4.Sporangiophores cut at 5 mm above the base regenerated less frequently than after decapitation and the decrease was larger in stage 4 than in stage 1. Hyphae and sporangiophores regenerated alone or together, but hyphae were most common on attached stage 1 stumps. Regeneration was always from the wound closure wall, and two or more sporangiophore initials per parent were less frequent on stumps than near the apex.Observations on outflowing of drops of cell contents and on wound closure are discussed in relation to regeneration.