Ultrastructural development of merosporangia in the mycoparasite Piptocephalis indica

Abstract

Transmission and scanning electron microscopy were used to study the ultrastructural development of merosporangia of Piptocephalis indica. Merosporangial branches were initiated from heart-shaped basal-spore initials on dichotomously branched sporangiophores. After elongation, spores were cleaved out of the merosporangial protoplast by simultaneous invagination of the plasmalemma. The plasmalemmal invaginations fused at the center of the merosporangium and delimited a varying number of more or less equal-sized spores in a single row. At maturity. spores had an inner, electron-transparent wall layer and an outer, electron-opaque wall layer. Mature spores possessed scars at each end with the basal spore having scars at each point of merosporangial disarticulation. Fertile branches were highly vacuolated at the time of spore detachment. Development of merosporangiospores in P. indica is similar to that in Syncephalis sphaerica at the early cleavage stages with some differences evident at postcleavage.