Ontogenetic and histochemical studies of the apothecium of -Sclerotinia sclerotiorum

Histochemical studies on mature sclerotia of Sclerotinia sclerotiorum showed that they contain high concentrations of proteins, glycogen and lipids; the activities of nine selected enzymes were low to moderate in them. Apothecial initials were first discernible in the sclerotia as small centra or nests of hyphae. No evidence of spermatization was detected prior to initiation. Tyrosinase, laccase, acid and alkaline phos-phatases, esterase, malate, isocitrate, succinate and glucose-6-phosphate dehydrogenases were highly active in the initials; intense staining was observed for glycogen and proteins. After emergence through the sclerotial rind the initial elongated rapidly and there was an accumulation of proteins and glycogen at its base. Activities of the selected enzymes were very high in the emerged initials but remained low in sclerotial hyphae. The morphological and cytological details of disc development are similar to those described for other Discomycetes. The activities of all enzymes studied, except tyrosinase, were high in the sub-hymenium of the disc; proteins and glycogen were concentrated in this region. In the stipe, degrading enzymes were of moderate to high activity; all the other enzymes were moderately active except laccase, which gave an intense staining reaction in the outer regions of the stipe.