The structure and development of haustorial placentas in leptosporangiate ferns provide a clear-cut distinction between euphyllophytes and lycophytes.

ABSTRACT: This light and electron microscope study revealed that leptosporangiate ferns have highly distinctive gametophyte-sporophyte junctions characterized by sporophytic haustoria, the absence of intraplacental spaces and degenerating cells, and the early appearance of wall ingrowths in both generations. Other notable cytological features are highly pleomorphic plastids and mitochondrial aggregates in the gametophytic placental cells. Close similarities with the gametophyte-sporophyte junctions in Tmesipteris and major differences from those of homosporous lycophytes are in line with the placement of psilophytes and ferns in the same clade and distance both from lycophytes. A smooth interface between the two generations in Azolla suggests a clear-cut discontinuity between homosporous and heteros

SUBMITTER: Duckett JG 

PROVIDER: S-EPMC4243667 | biostudies-literature | 2003 Oct

REPOSITORIES: biostudies-literature