Spermatogenesis in Lycopodium: The Mature Spermatozoid

Robbins, Robert R.; Carothers, Zane B.

doi:10.2307/2442700

Cited by 19 publications

(17 citation statements)

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“…Flagella are slightly staggered in the smaller coiled sperm cells of Huperzia and Lycopodium and more widely separated in the more specialized ovoid cells of Palhinhaea and Lycopodiella. These ideas are contrary to those of Robbins & Carothers (1978), who speculated that an ovoid cell with widely spaced £agella is the primitive condition in archegoniates. The only homosporous lycophyte with multi£agellated sperm (ca.…”

Section: Spermatogenesiscontrasting

confidence: 62%

Vegetative and reproductive innovations of early land plants: implications for a unified phylogeny

Renzaglia

Rjt

Nickrent

et al. 2000

Phil. Trans. R. Soc. Lond. B

213

165

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As the oldest extant lineages of land plants, bryophytes provide a living laboratory in which to evaluate morphological adaptations associated with early land existence. In this paper we examine reproductive and structural innovations in the gametophyte and sporophyte generations of hornworts, liverworts, mosses and basal pteridophytes. Reproductive features relating to spermatogenesis and the architecture of motile male gametes are overviewed and evaluated from an evolutionary perspective. Phylogenetic analyses of a data set derived from spermatogenesis and one derived from comprehensive morphogenetic data are compared with a molecular analysis of nuclear and mitochondrial small subunit rDNA sequences.Although relatively small because of a reliance on water for sexual reproduction, gametophytes of bryophytes are the most elaborate of those produced by any land plant. Phenotypic variability in gametophytic habit ranges from leafy to thalloid forms with the greatest diversity exhibited by hepatics. Appendages, including leaves, slime papillae and hairs, predominate in liverworts and mosses, while hornwort gametophytes are strictly thalloid with no organized external structures. Internalization of reproductive and vegetative structures within mucilage-¢lled spaces is an adaptive strategy exhibited by hornworts. The formative stages of gametangial development are similar in the three bryophyte groups, with the exception that in mosses apical growth is intercalated into early organogenesis, a feature echoed in moss sporophyte ontogeny.A monosporangiate, unbranched sporophyte typi¢es bryophytes, but developmental and structural innovations suggest the three bryophyte groups diverged prior to elaboration of this generation. Sporophyte morphogenesis in hornworts involves non-synchronized sporogenesis and the continued elongation of the single sporangium, features unique among archegoniates. In hepatics, elongation of the sporophyte seta and archegoniophore is rapid and requires instantaneous wall expandability and hydrostatic support. Unicellular, spiralled elaters and capsule dehiscence through the formation of four regular valves are autapomorphies of liverworts. Sporophytic sophistications in the moss clade include conducting tissue, stomata, an assimilative layer and an elaborate peristome for extended spore dispersal. Characters such as stomata and conducting cells that are shared among sporophytes of mosses, hornworts and pteridophytes are interpreted as parallelisms and not homologies.Our phylogenetic analysis of three di¡erent data sets is the most comprehensive to date and points to a single phylogenetic solution for the evolution of basal embryophytes. Hornworts are supported as the earliest divergent embryophyte clade with a moss/liverwort clade sister to tracheophytes. Among pteridophytes, lycophytes are monophyletic and an assemblage containing ferns, Equisetum and psilophytes is sister to seed plants. Congruence between morphological and molecular hypotheses indicates that these data sets are tracking the...

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Section: Spermatogenesiscontrasting

confidence: 62%

Vegetative and reproductive innovations of early land plants: implications for a unified phylogeny

Renzaglia

Rjt

Nickrent

et al. 2000

Phil. Trans. R. Soc. Lond. B

213

165

View full text Add to dashboard Cite

show abstract

“…These studies have also uncovered diagnostic features of lycopsid gametes, and they have revolutionized interpretations of evolutionary trends in spermatozoid structure (see below). Unpublished data on Huperzia, Phylloglossum, Diphasiastrum, and Isoëtes coupled with published studies of Selaginella (Robert, 1973(Robert, , 1974 and three generic segregates of Lycopodium (Palhinhaea, Robbins and Carothers, 1978;Lycopodium, Maden et al, 1996;Lycopodiella, Maden et al, 1997) provide an initial overview of sperm cell diversity in this assemblage (Figures 6 to 8). Major structural differences among lycophyte sperm cells include flagellar number, cell shape, and organellar number and position.…”

Section: Mature Cell Architecturementioning

confidence: 98%

“…By the early 1990s, midstage and mature sperm had been examined in all major groups of archegoniates, that is, bryophytes, lycophytes, pteridophytes, and seed plants (Carothers and Rushing, 1988;Duckett, 1988, 1991;Robbins and Carothers, 1978;Robert, 1974;Norstog, 1974). Because these cells and their development are clearly homologous, this led to the construction of an extensive data set for application in phylogenetic analysis.…”

Section: Introduction and Historymentioning

confidence: 99%

Motile Gametes of Land Plants: Diversity, Development, and Evolution

Renzaglia

Garbary

2001

Critical Reviews in Plant Sciences

128

107

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“…Most notable are a cloud of electron-opaque material interspersed among basal bodies in ferns, the so-called amorphous zone (Hoffman et al, 1994;Hoffman and Vaughn, 1995), and the lamellar strip of the MLS (Duckett, 1975;Maden et al, 1996Maden et al, , 1997Renzaglia and Duckett, 1987;Renzaglia et al, 1999;Robbins and Carothers, 1978). At the close of the final cell division in the fern Ceratopteris, mature basal bodies are embedded in electron-dense pericentriolar material (Hoffman et al, 1994).…”

Section: Mtocs In Developing Sperm Cellsmentioning

confidence: 99%

“…Compared to the smaller biflagellated cells (6 -10 m in length) of other members of the Lycopodiaceae (Maden et al, 1996(Maden et al, , 1997Robbins and Carothers, 1978), the sperm cells of Phylloglossum are large (about 16 m in length) and contain approximately 20 flagella (Renzaglia and Whittier, 1993). Centrioles originate in the spermatid mother cells as a unique branched organelle that is structurally divergent from the blepharoplast produced by other land plants with multiflagellated sperm (Garbary et al, 1993;Renzaglia et al, 2000).…”

Section: Introductionmentioning

confidence: 99%