Embryogeny and Reproductive Biology of Bothrodendrostrobus mundus (Lycopsida)

Stubblefield, Sara P.; Rothwell, Gar W.

doi:10.2307/2442789

Cited by 22 publications

(20 citation statements)

References 12 publications

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“…The description of embryos in Lepidocarpon (Phillips, Avein and Schopf, 1975 ;Phillips, 1979) allows us to interpret Stigmaria as originating from the first dichotomy of the stem. This realization provides confirmation of the hypothesis that Stigmaria is a shoot modified for rooting, and that arborescent lycophytes have secondarily derived bipolar growth (Stubblefield and Rothwell, 1981).…”

supporting

confidence: 79%

The Apex of Stigmaria (Lycopsida), Rooting Organ of Lepidodendrales

Rothwell

1984

American Journal of Botany

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An apical segment of Stigmaria ficoides recently has been located among specimens from Pennsylvanian sediments of Iowa, and provides the first indisputable structural evidence for apical organization and development in one of the mostenigmatic of all tracheophyte organs. Toward the apex, the specimen tapers to a circular rim. Rootlet scars occur in a helical arrangement from the proximal end of the specimen to the margin of the rim. Within the rim there is a discontinuous groove that surrounds an irregularly concave apex. The specimen compares favorably with the rooting apex of young Nathorstiana specimens, and adds to our knowledge of homologies among lycophyte rhizomorphs with axial elongation.

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confidence: 79%

The Apex of Stigmaria (Lycopsida), Rooting Organ of Lepidodendrales

Rothwell

1984

American Journal of Botany

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“…the rhizomorphic system) are essentially the same and are assigned to the fossil morphogenus Stigmaria; they consist of extensive shallow branch systems that functioned as roots in providing anchorage and uptake of water and nutrients. While it might be argued that the rhizomorphic system represents some intermediate stage in root evolution, the anatomy and development (including embryology) of these peculiar below-ground organs indicate that the rooting structures of all rhizomorphic lycopsids represent shoots (Stubblefield & Rothwell, 1981), in which the ultimate units (termed appendages or rootlets) are greatly modified leaves that develop exogenously (Rothwell & Erwin, 1985). Stigmarian appendages are up to 40 cm long and typically < 0.5-1 cm wide (Taylor et al, 2009).…”

Section: Arbuscular Mycorrhizal-like Fungi In Carboniferous Arborescementioning

confidence: 99%

Arbuscular mycorrhizal‐like fungi in Carboniferous arborescent lycopsids

Krings

Taylor

et al. 2011

New Phytologist

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“…The modified shoot hypothesis got more support toward the end of the 20th century. The discovery of fossilized embryos showing that the shoot and root axes were derived from a branching event during embryogenesis (16,29), the documentation that rootlet abscission resembled foliar abscission (17,18), observations on well-preserved fossil rhizomorph apices (30)(31)(32), and their interpretation within a phylogenetic context (31,33) led to a complete revival of Schimper's (27) modified shoot hypothesis.…”

mentioning

confidence: 99%

Networks of highly branched stigmarian rootlets developed on the first giant trees

Hetherington

Berry

Dolan

2016

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

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Lycophyte trees, up to 50 m in height, were the tallest in the Carboniferous coal swamp forests. The similarity in their shoot and root morphology led to the hypothesis that their rooting (stigmarian) systems were modified leafy shoot systems, distinct from the roots of all other plants. Each consists of a branching main axis covered on all sides by lateral structures in a phyllotactic arrangement; unbranched microphylls developed from shoot axes, and largely unbranched stigmarian rootlets developed from rhizomorphs axes. Here, we reexamined the morphology of extinct stigmarian systems preserved as compression fossils and in coal balls from the Carboniferous period. Contrary to the long-standing view of stigmarian systems, where shoot-like rhizomorph axes developed largely unbranched, root-hairless rootlets, here we report that stigmarian rootlets were highly branched, developed at a density of ∼25,600 terminal rootlets per meter of rhizomorph, and were covered in root hairs. Furthermore, we show that this architecture is conserved among their only extant relatives, herbaceous plants in the Isoetes genus. Therefore, despite the difference in stature and the time that has elapsed, we conclude that both extant and extinct rhizomorphic lycopsids have the same rootlet system architecture.evolution | paleobotany | Carboniferous forests | stigmarian root systems | Isoetes T he spread of the first wetland forests with tall trees during the Carboniferous period (359-300 million years ago) had a dramatic impact on the carbon cycle by burying large amounts of organic carbon in the form of peat in coal swamps (1, 2). Lycophyte trees up to 50 m in height (3, 4) were dominant components of coal swamp forests (5, 6). They were key components of coal-forming environments throughout the Carboniferous period but dominated in the lower-middle Pennsylvanian (Namurian-Wetsphalian) where they typically contribute between 60% and 95% of the biomass in buried peat (7-13). The preserved remains of lycophyte trees form some of the most extensive fossil plant deposits of any geological period. This is in part because of their size and ecological dominance but also the result of the high probability of preservation in the waterlogged conditions in which these trees grew (4). Detailed descriptions of the morphology of these plants on a range of scales-from entire in situ tree lycophyte forests (14, 15) to cellular descriptions of developing spores (16)-have made these trees some of the best understood fossil plants of the Carboniferous coal swamps.The rooting system of the arborescent lycopsids-stigmarian systems-consist of large shoot-like axes (rhizomorphs) that develop lateral organs called rootlets (4,(17)(18)(19)(20). Rootlets, which have been described as largely unbranched and root hairless (4,5,(17)(18)(19)(20)(21)(22)(23)(24), are arranged in a characteristic pattern or rhizotaxy on the rhizomorph (25). It is the arrangement of these largely unbranched leaf-like rootlets on a shoot-like axis that first led to the theory that stigm...

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Embryogeny and Reproductive Biology of Bothrodendrostrobus mundus (Lycopsida)

Cited by 22 publications

References 12 publications

The Apex of Stigmaria (Lycopsida), Rooting Organ of Lepidodendrales

The Apex of Stigmaria (Lycopsida), Rooting Organ of Lepidodendrales

Arbuscular mycorrhizal‐like fungi in Carboniferous arborescent lycopsids

Networks of highly branched stigmarian rootlets developed on the first giant trees

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