Spores in earliest land plants

Taylor, Wilson A.

doi:10.1038/373391b0

Cited by 59 publications

(35 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lamellae are considered to be produced at some point during the ontogeny of virtually all land plant spores/pollen, and may be present in a variety of forms and positions in many mature spore/pollen walls. However, spores/ pollen in which continuous, parallel-arranged lamellae are present at maturity throughout the walls are confined to extant liverworts 16,22 , suggesting that the Ordovician plants from Oman may have liverwort affinities. This reinforces claims for liverwort affinities based on morphology of Ordovician spores, and conforms to land plant phylogenies that place liverworts as basal.…”

mentioning

confidence: 99%

“…In fact, some of the permanent tetrads, including envelope-enclosed forms, closely resemble the spores of extant liverworts 2 . Third, wall ultrastructure in Ordovician cryptospores is varied, but in some morphotypes suggests affinities with extant liverworts 16 . Fourth, and rather intriguingly, some of the earliest known land plant mesofossils/ megafossils from the latest Silurian to earliest Devonian contain spores similar in morphology to the Ordovician forms (for example, permanent tetrads and dyads) [17][18][19][20] .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Fragments of the earliest land plants

Wellman

Osterloff

Mohiuddin

2003

Nature

508

303

View full text Add to dashboard Cite

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Fragments of the earliest land plants

Wellman

Osterloff

Mohiuddin

2003

Nature

508

303

View full text Add to dashboard Cite

show abstract

“…Preservation of such delicate structures demonstrates that the homogeneity of the walls in the in situ permanent dyads and tetrads from the same locality is not caused by diagenesis. However, such ultrastructural simplicity, mirrored in early dispersed taxa such as the Late Ordovician/Early Silurian Tetrahedraletes medinensis (Taylor 1995a) and Pseudodyadospora sp. (Taylor 1996) frustrates attempts to detect a¤nities using this character.…”

Section: (B) In Situ Dyadsmentioning

confidence: 99%

“…with sutures separating spores) assigned to Tetrahedraletes occur in the bifurcating specimen (¢gure 3e^g), and in a number of spore masses. While ultrastructural studies have been useful in demonstrating diversity in these laevigate forms, the most complex exospores, comparable with the lamellate exospores of Dyadospora murusdensa (Taylor 1995a(Taylor , 1996 and D. murusattenuata in part (Taylor 1997), are in spore masses. The only illustrated ultrastructure from Upper Ordovician tetrads is from Tetrahedraletes medinensis where the exospore is homogeneous (Taylor 1995b) and thus similar to some of the Lower Devonian examples (see Edwards et al 1999; ¢gure 3g) although an exfoliating outer layer has not been reported in the older forms.…”

Section: (I) Comparisons With Dispersed Sporesmentioning

confidence: 99%

“…Its critical reappraisal has been stimulated recently by suggestions that distinctive spores recorded from Ordovician rocks, which are considered the earliest evidence of land plants, were produced by plants at the bryophyte grade (Gray 1985;Taylor 1995aTaylor ,b, 1997 and by the need to test phylogenetic hypotheses based on cladistic analyses of embryophytes (e.g. Mishler et al 1994).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The role of Mid-Palaeozoic mesofossils in the detection of early bryophytes

Edwards

2000

Phil. Trans. R. Soc. Lond. B

View full text Add to dashboard Cite

Recently discovered Silurian and Devonian coali¢ed mesofossils provide an additional source of data on early embryophytes. Those reviewed in this paper are considered of some relevance to understanding the early history of bryophytes while highlighting the di¤culties of recognizing bryophytes in often very fragmentary fossils. The ¢rst group comprises sporophytes in which terminal sporangia contain permanent dyads and tetrads. Such spores (cryptospores) are similar to those found dispersed in older Ordovician and Silurian strata, when they are considered evidence for a land vegetation of embryophytes at a bryophyte grade. The phylogenetic signi¢cance of plants, where the axes associated with both dyadand tetrad-containing sporangia are branching, a character state not found in extant bryophytes, is discussed. The second group comprises axial fossils, many with occasional stomata, in which central conducting strands include G-type tracheids and a number of novel types of elongate elements not readily compared with those of any tracheophyte. They include smooth-walled, evenly thickened elongate elements as well as those with numerous branching § anastomosing projections into the lumen. Some of the latter bear an additional microporate layer, but the homogenized lateral walls between adjacent cells are never perforate. Such cells, which occur in various combinations in central strands, are compared with the leptoids and hydroids of mosses, hydroids of liverworts and presumed water-conducting cells in coeval Lower Devonian plants such as Aglaophyton. It is concluded that lack of information on the chemistry of their walls hampers sensible assessment of their functions and the a¤nities of the plants. Finally, a minute fossil, comprising an elongate sporangium in which a central cylindrical cavity containing spores and possible elaters terminates in a complex poral dehiscence apparatus, is used to exemplify problems of identifying early bryophytes. It is concluded that further progress necessitates the discovery of pre-Upper Silurian fossils with well-preserved anatomy, as well as a re-evaluation of criteria used to assess existing and new Devonian fossils for bryophyte a¤nity.

show abstract

Occurrence and evolutionary significance of RESISTANT CELL WALLS IN CHAROPHYTES AND BRYOPHYTES

Kroken

Graham

Cook

1996

American J of Botany

View full text Add to dashboard Cite

A survey of charophycean green algal and bryophyte taxa revealed the frequent occurrence of vegetative cell walls that were characterized by a specific form of autofluorescence and resistance to high temperature acid treatment (acetolysis). The time of production and the location of resistant, autofluorescent cell walls varied among charophyte and bryophyte taxa in patterns that suggest that bryophytes inherited the capacity to produce such walls from charophyte ancestors. A number of charophytes produced resistant walls in response to desiccation stress, suggesting an evolutionarily early adaptive response. Coleochaete was unique among charophytes, but similar to all bryophytes tested in that sexual reproduction induced autofluorescence in cell walls of well‐hydrated tissues at the placental junction. Maternal tissues in apical portions of the pseudoseta bearing Sphagnum sporophytes were characterized by autofluorescent, acetolysis‐resistant cell walls similar to those observed in maternal cells adjacent to Coleochaete zygotes. These observations suggest that cell–cell stimulus–response interactions regulate deposition of autofluorescent compounds in placental cell walls, and that this characteristic may have been shared by the earliest embryophytes and their charophyte ancestors. Various bryophytes deposit autofluorescent, acid‐resistant compounds at other adaptively significant sites including sporangial epidermis, spiral thickenings of elaters, rhizoids, and leaves in the special case of Sphagnum moss. Sphagnum and liverwort sporangial epidermis, which had been subjected to acetolysis or strong acid procedures commonly used to release microfossils from rock matrices, resembled published photographs of Ordovician–Devonian microfossils consisting of cellular scraps that have been attributed to earliest land plants. Our work suggests that at least some of these fossils, previously thought to represent “dispersed cuticles,” could be reinterpreted as earliest known remains of plant sporophytic tissues, and that they may be homologous with resistant sporangial epidermis of modern bryophytes. In general, the patterns of occurrence of resistant, autofluorescent cell walls in charophytes and bryophytes suggest repeated exaptation. Regulation of deposition appears to have been modified through time, so that resistant wall compounds have had a sequence of functions: desiccation resistance and/or microbial resistance in lower charophytes, a role in embryogenesis in Coleochaete and embryophytes, and finally, decay resistance in innovative structures that characterize bryophytes, such as rhizoids, sporangial epidermis, and elaters.

show abstract

Spores in earliest land plants

Cited by 59 publications

References 4 publications

Fragments of the earliest land plants

Fragments of the earliest land plants

The role of Mid-Palaeozoic mesofossils in the detection of early bryophytes

Occurrence and evolutionary significance of RESISTANT CELL WALLS IN CHAROPHYTES AND BRYOPHYTES

Contact Info

Product

Resources

About