The ultrastructure of fossil gymnosperm pollen

Taylor, Thomas N.; Taylor, Edith L.

doi:10.1080/01811789.1987.10826868

Cited by 12 publications

(11 citation statements)

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“…The same material was examined in detail, included TEM analysis of the spores, by Taylor and Scheckler (1996) (see p. 18). Other authors who have reviewed the in situ occurrence of R. langii in T. schmidtii are Andrews in Boureau (1970), Allen (1980), Gensel (1980), Taylor (1981), Gensel and Andrews (1984), Taylor and Taylor (1987) and Balme (1995). Interestingly, Bonamo and Banks (1967) noted that some of the in situ spores were three‐layered.…”

Section: In Situ Occurrences Of Rhabdosporites Langiimentioning

confidence: 99%

ULTRASTRUCTURE OF DISPERSED ANDIN SITUSPECIMENS OF THE DEVONIAN SPORERHABDOSPORITES LANGII: EVIDENCE FOR THE EVOLUTIONARY RELATIONSHIPS OF PROGYMNOSPERMS

Wellman¹

2008

Palaeontology

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Abstract:The spore Rhabdosporites (Triletes) langii (Eisenack) Richardson, 1960 is abundant and well preserved in Middle Devonian (Eifelian) 'Middle Old Red Sandstone' deposits from the Orcadian Basin, Scotland. Here it occurs as dispersed individual spores and in situ in isolated sporangia. This paper reports on a detailed light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis of both dispersed and in situ spores. The dispersed spores are pseudosaccate with a thick walled inner body enclosed within an outer layer that was originally attached only over the proximal face. The inner body has lamellate ⁄ laminate ultrastructure consisting of fine lamellae that are continuous around the spore and parallel stacked. Towards the outer part of the inner body these group to form thicker laminate structures that are also continuous and parallel stacked. The outer layer has spongy ultrastructure. In situ spores preserved in the isolated sporangia are identical to the dispersed forms in terms of morphology, gross structure and wall ultrastructure. The sporangium wall is two-layered. A thick coalified outer layer is cellular and represents the main sporangium wall. This layer is readily lost if oxidation is applied during processing. A thin inner layer is interpreted as a peritapetal membrane. This layer survives oxidation as a tightly adherent membranous covering of the spore mass. Ultrastructurally it consists of three layers, with the innermost layer composed of material similar to that comprising the outer layer of the spores. Based on the new LM, SEM and TEM information, consideration is given to spore wall formation. The inner body of the spores is interpreted as developing by centripetal accumulation of lamellae at the plasma membrane. The outer layer is interpreted as forming by accretion of sporopollenin units derived from a tapetum. The inner layer of the sporangium wall is considered to represent a peritapetal membrane formed from the remnants of this tapetum. The spore R. langii derives from aneurophytalean progymnosperms. In light of the new evidence on spore ⁄ sporangium characters, and hypotheses of spore wall development based on interpretation of these, the evolutionary relationships of the progymnosperms are considered in terms of their origins and relationship to the seed plants. It is concluded that there is a smooth evolutionary transition between Apiculiretusisporatype spores of certain basal euphyllophytes, Rhabdosporitestype spores of aneurophytalean progymnosperms and Geminospora-⁄ Contagisporites-type spores of heterosporous archaeopteridalean progymnosperms. Prepollen of basal seed plants (hydrasperman, medullosan and callistophytalean pteridosperms) are easily derived from the spores of either homosporous or heterosporous progymnosperms. The proposed evolutionary transition was sequential with increasing complexity of the spore ⁄ pollen wall probably reflecting increasing sophistication of reproductive strategy. The pollen wall of crown group ...

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Section: In Situ Occurrences Of Rhabdosporites Langiimentioning

confidence: 99%

ULTRASTRUCTURE OF DISPERSED ANDIN SITUSPECIMENS OF THE DEVONIAN SPORERHABDOSPORITES LANGII: EVIDENCE FOR THE EVOLUTIONARY RELATIONSHIPS OF PROGYMNOSPERMS

Wellman¹

2008

Palaeontology

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“…They are sub cir cu lar, granulate/punctate, with a trilete proximal scar, and indistinguishable from spores in dispersed state. The ultrastructure of prepollen grains extracted from Crossotheca hughesiana also confirms the primitiveness of the order: the only aperture is the proximal scar, and the ultrastructure of the sporoderm is homogeneous (Taylor & Taylor 1987; fig. 7).…”

Section: Development Of a Distal Aperture In Primitive Prepollen: Thementioning

confidence: 58%

Evolutionary Transformations of Sporoderm Ultrastructure in Certain Monophyletic Lineages of Higher Plants

Zavialova¹

2015

Bot Pac

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A B S T R A C TData of transmission electron microscopy can be successfully used to reveal evolutionary transformations, which occurred in pollen or spores during the exis tence of monophyletic lineages of higher plants. On the basis of such data, one can discover gradual transitions in groups, which include new forms, that at the first glance seem to be totally dissimilar to the predecessors. One can trace se quences of morphological transitions within lineages from the earliest to latest mem bers of a given group and connect the first and last members, which do not share any common features. Hidden transformations are traceable in groups, which seemed unchanged during the entire period of their existence. Parallelisms can be revealed between unrelated groups of higher plants not only in final forms, but also in succession of transformations. The successful application of this ap proach has been exemplified in lyginopteridaleans, peltasperms, equisetaleans, and the Cheirolepidiaceae. Particularly promising seem groups that have a long geological history and survive until now. Данные трансмиссионной электронной микроскопии могут с успехом применяться для выявления эволюционных преобразований в ультраструк туре пыльцевых зерен или спор, происходивших в монофилетических ли ни ях высших растений. На основе таких данных можно находить по сте пен ные переходы в тех случаях, когда новые и совершенно не похожие на предшественников формы возникали в геологической летописи на первый взгляд внезапно. Можно прослеживать последовательные морфологиче ские преобразования в ряду от самых ранних к самым поздним представите лям определенной группы, что удается даже если между первыми и послед ними членами цепи вообще не наблюдается сходных признаков. Скрытые преобразования удается проследить в группах, казалось бы остававшихся практически не измененными в течение всего периода их сущест вования. Могут быть выявлены параллелизмы между неродственными группами выс ших растений, касающиеся не только отдельных стадий, но и последова тельностей преобразований, которые к этим стадиям привели. В качестве примеров рассмотрены лигиноптерисовые и пельтаспермовые семенные папоротники, хвощи, хейролепидиевые. Особенно перспективными пред ставляются группы, имеющие длительную геологическую историю и до жившие до настоящего времени.

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“…Comparison with extant and fossil taxa-Details now available on the structure of Sahnia pollen remove an important gap in previous knowledge of the Pentoxylales (Crane, 1985) and contribute to the accumulating information on the micromorphology and ultrastructure of in situ fossil gymnosperm pollen (Taylor and Taylor, 1987;Taylor, 1988). These new data therefore provide an improved basis for comparing the pollen of Pentoxylales with that of other seed plants.…”

Section: Discussionmentioning

confidence: 99%

“…Several features distinguish Sahnia pollen from the grains of other extant and fossil gymnosperms (Table 1). The absence of a saccus distinguishes Sahnia pollen from that of most conifers (including the earliest fossil representatives of the group), cordaites, and several groups of 'seed ferns' including Caytoniales, Corystospermales, and Glossopteridales (see Taylor and Taylor, 1987;Taylor, 1988 for review). Sahnia pollen is ovoid in shape and has a distal sulcus; this also distinguishes it from pollen of certain conifers that have spheroidal, inaperturate grains (e.g., Araucaria), as well as medullosan and lyginopterid 'seed ferns' in which the pollen has a proximal trilete or monolete mark rather than a distal sulcus (Taylor and Taylor, 1987;Taylor, 1988).…”

Section: Discussionmentioning

confidence: 99%

“…Preliminary fine structural analyses of Sahnia pollen, employing electron microscopy, were provided by Taylor and Taylor (1987) and Taylor (1988) as part of a comprehensive review of sporoderm ultrastructure in fossil gymnosperms. The present study expands these earlier observations, provides additional details of the ultrastructure and micromorphology of in situ Sahnia laxiphora pollen grains, and contributes new data with which to assess the systematic affinities of the Pentoxylales.…”

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confidence: 99%

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The Ultrastructure of Sahnia Pollen (Pentoxylales)

Osborn

Taylor

Crane

1991

American Journal of Botany

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The micromorphology and fine structure of in situ pentoxylalean pollen are described from the holotype of Sahnia laxiphora Drinnan and Chambers 1985 collected from the Lower Cretaceous (Valanginian-Aptian) of Victoria, southeastern Australia. Pollen grains are ovoid, monosulcate, and relatively small, averaging 26 !Lm in length. Exine ornamentation is psilate. The sporoderm is two-parted with the sexine staining lightly throughout and approximately six times the thickness of the more darkly staining nexine. The exine over the sulcus is typically strongly invaginated, and mayor may not include an extremely thin sexine layer. The outer part of the sexine is homogeneous, while the inner part is composed of relatively large granules separated by irregular lacunae of various sizes; lacunae are most pronounced at the sexinenexine interface. Faint lamellae characterize the nexine in both apertural and nonapertural regions. Granular orbicules are often associated with the exine surfaces and also occur appressed to pollen sac walls along with lamellated tapetal membranes. Sporoderm ultrastructure is compared to that of nonsaccate pollen of other groups, and particularly to pollen of Bennettitales, Gnetales, angiosperms, and similar plants, to which the Pentoxylales have been thought to be closely related. Although Sahnia laxiphora pollen is not identical to that of any of these taxa, the strongest similarity is with pollen of Bennettitales.

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The ultrastructure of fossil gymnosperm pollen

Abstract: Summary.-The ultrastructure of fossil gymnosperm pollen is reviewed based on studies of in situ grains. The following groups contain taxa that have been investigated at the ultrastructural level :

Cited by 12 publications

References 26 publications

ULTRASTRUCTURE OF DISPERSED ANDIN SITUSPECIMENS OF THE DEVONIAN SPORERHABDOSPORITES LANGII: EVIDENCE FOR THE EVOLUTIONARY RELATIONSHIPS OF PROGYMNOSPERMS

ULTRASTRUCTURE OF DISPERSED ANDIN SITUSPECIMENS OF THE DEVONIAN SPORERHABDOSPORITES LANGII: EVIDENCE FOR THE EVOLUTIONARY RELATIONSHIPS OF PROGYMNOSPERMS

Evolutionary Transformations of Sporoderm Ultrastructure in Certain Monophyletic Lineages of Higher Plants

The Ultrastructure of Sahnia Pollen (Pentoxylales)

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