Spore germination and microcycle conidiation of two penicillia in soil [Penicillium daleae, Penicillium bilau, Fungi]

Laboratory-produced spores of two penicillia isolated from soil were placed onto PVC membrane filters, inserted into microholders and buried in the A horizon of an oak-birch forest. After various intervals of time incubation filters were retrieved, stained, and mounted on glass slides for examination. Characteristics of growth and germination of Penicillium daleae and P. bilaii in the laboratory and in the soil were then compared. Spores of these indigenous soil fungi, reinoculated into the soil, germinated slowly, requiring several days for swelling and germ tube protrusion. The most significant observation was the occurrence of a microcycle in which germ tube volume was reduced, mycelial growth was eliminated, and conidiation consisted of a diminution in complexity of reproductive structures by decreasing the number of phialides in the penicillus and reducing spore volume.