The Gametophyte Generation of Some Early Devonian Land Plants

Remy, Winfried; Gensel, Patricia G.; Hass, Hagen

doi:10.1086/297089

Cited by 118 publications

(78 citation statements)

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“…Based on these ideas, the prototypic spermatozoid of archegoniates was probably a minute bi£agellated cell with minimal sinistral coiling. Observations of remarkably well-preserved sperm cells in Devonian gametophytes strengthen the speculation that primitive land plants produced small coiled gametes (Remy et al 1993;Duncan et al 1997). …”

Section: Spermatogenesissupporting

confidence: 52%

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: Spermatogenesissupporting

confidence: 52%

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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“…Information about the gametophytic phase in early land plants was speculative until the discovery of free-living gametophytes in the Rhynie chert (24). Since then, various aspects of the gamete-producing phase of several Rhynie chert macroplants have been described, and it is now possible to present a more complete picture of life histories in some early land plants (25)(26)(27). Here, we document the development of the gametophyte of Aglaophyton major from the germination of spores to the formation of mature gametangia on sexually dimorphic gametophytes.…”

Section: Resultsmentioning

confidence: 99%

Life history biology of early land plants: Deciphering the gametophyte phase

Taylor

Kerp

Hass

2005

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

166

104

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The ca. 400-million-year-old Rhynie chert biota represents a benchmark for studies of early terrestrial ecosystems. The exquisite preservation of the organisms documents an ancient biodiversity that also includes various levels of biological interaction. Absent from the picture until recently has been detailed information about the development of the gametophyte phase and the alternation of generations of the macroplants in this ecosystem. Here, we trace the development of the gametophyte phase of Aglaophyton, an early land plant with an unusual complement of structural and morphological characters. Mature gametophytes consist of a fleshy protocorm attached to the substrate by basal rhizoids; arising from the upper surface are one to several upright gametangiophores bearing multiple gametangia. Stomata are present on the upper surface of the protocorm and gametangiophore, and endomycorrhizal fungi extend throughout the gametophyte. Gametophytes are unisexual, producing either antheridiophores or archegoniophores. There is no evidence that gametophytes later become hermaphroditic. The sexual dimorphism of the Rhynie chert gametophytes is inconsistent with theoretical ideas about the haploid phase of early land plants. The gametophyte phase of early land plants can now be considered within an ecological and evolutionary framework that, in turn, can be used to develop hypotheses about some aspects of the population dynamics and growth of these early land plants.Early Devonian ͉ fossil gametophytes ͉ Rhynie chert ͉ spore development ͉ alteration of generations

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“…Second, these gametophytes produced archegoniophores that elevated archegonia above the substrate. Third, no gametophytes have been found with attached sporophytes (Remy, 1980;Remy et al, 1993;Taylor et al, 2005).…”

Section: Homologous Alternation Reduxmentioning

confidence: 99%