Ultrastructural Observations on the Septal Pore inCronartium Flaccidum(Alb. Et Schw.) Wint. Also in Relation to the Taxonomy of the Uredinales

Abstract

SUMMARY -The fine structure of the septum and pore in the monokaryotic and dikaryotic vegetative mycelium of Cronartium flaccidum was studied. Some ultrastructural observations on the hyphal cell of this fungus were also carried out. The hyphal septa become progressively thinner towards the pore; the septal pore shows none of the swellings and of the structures resembling the parenthesome which characterize the dolipore septum of higher Basidiomycetes. The septal pore of C. flaccidum as it as been seen in other Uredinales investigated up now, is a very simple structure morphologically similar to the septal pore of Ascomycetes. Some formations which make up the septal pore apparatus that is amorphous and electron-dense material, differentiated organelle-free cytoplasm and microbodies were observed near the septum and pore in both nuclear phases of the mycelium. It is accepted a relationship between the occurrence of microbodies and the occurrence and function of the dense material at the pore region likely to be associated with eventual migrations of nuclei and other cytoplasmic organelles. The taxonomic importance of the septum and pore fine structure for the systematic assessment of the Uredinales within the Basidiomycetes is discussed.

Models of cell differentiation in conidial fungi.

“…Ingrowth of the septum in this case culminates in a marked increase in wall synthesis and differentiation in the region of the central pore. Morphological intergradations between these two basic types of septa are recognized (262,281,405), as well as certain artifacts of dolipore septal ultrastructure (213), and the phylogenetic implications of such characters are uncertain (201). Nevertheless, identification of septal morphology has contributed significantly to considerations of whether a particular conidial fungus has an ascomycetous or basidiomycetous affinity (77).…”

Aeciospores of Cronartium flaccidum, C. ribicola and Endocronartium pini show no differences in morphology

“…The ultrastructure of Peridermium pini hyphae was studied in detail by WALLES (1974). LONGO (1982) compared these results with the ultrastructure of C. flaccidum but was unable to find any differences between these species. The IGS and ITS regions of the nuclear DNA of this species complex are obviously also closely related (MORIGGA et al 1996).…”

Ultrastructural Observations on the Dikaryotic Haustorium ofCronartium Flaccidum(Alb. & Schw.) Wint. inVincetoxicum HirundinariaMedicus

“…and embedded in Epon, using the technique already described in a previous work (LONGO 1982). Thin sections cut with a Reichert OMU3 ultramicrotome using glass knives, were stained with uranyl-acetate/lead-citrate and examined with a Philips EM300 electron microscope at 80 KV.…”

“…1981;KHAN et at. 1982;LoNGO et at. 1982;CoFFEY and ALLEN 1983); however in C. flaccidum endoplasmic reticulum vesicles are more frequent than cisternae.…”

“…Analogously, after conventional staining both in M-and D-haustoria of some rusts as in Dhaustorium of C. flaccidum, there has often been noted a greater affinity for Os04 of the extrahaustorial membrane than the uninvaginated host plasma membrane (LITTLEFIELD and HEATH 1979;KHAN et at. 1982;LONGO et at. 1982).…”