The ultrastructure of thePuccinia sorghi aecial stage

Abstract

In the aecium ofPuccinia sorghi the substantial outer layer of cell walls in the base of the stroma, together with the thick wall of peridial cells where they adjoin the compressed cell debris, may play a role in the water balance of the fruiting structure. With few exceptions binucleate cells are found only in the aecium. Cytoplasm of the binucleate peridial cells is densely filled with organelles and fat globules. Large multinucleate cells with inclusions, that are apparently proteinaceous in nature, are found in the aecial base. The ontogeny of aeciospore initials is annellidic and aeciosporophores have a well developed collar consisting of annellations. Sporophores, aeciospore initials, intercalary cells and young aeciospores are enveloped by a matrix. During aeciospore ontogeny fat globules are formed in the immediate vicinity of enlarging vacuoles and vesicle-containing structures, suggesting that the formation of fat globules is associated with these cytoplasmic components. Spine initials are first observed as electron-lucent areas between the plasmalemma and the wall of immature aeciospores. During further development the inter- and supraspinal wall of the spore is degraded, a process in which small, well-defined granules appear to be implicated. The spines become separated from the plasmalemma by wall apposition. Apposition also seals off the channel leading to the septal pore in the aeciospore base. The spore wall contains several germ pores. The vacuolate and often degenerate nature of inter- and intracellular hyphae in thalli with young sporulating aecia points to accumulation of food reserves in young aecia.