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Paula J Rudall - One of the best experts on this subject based on the ideXlab platform.
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Structure and abnormalities in Cones of the Wollemi pine (Wollemia nobilis)
Kew Bulletin, 2019Co-Authors: Veit M. Dörken, Paula J RudallAbstract:Reproductive structures of both genders of Wollemia nobilis were investigated, including both wild-type and teratological Cones. Typically, both pollen Cones and Seed Cones in this species are terminal on first order branches. At maturity, wild-type pollen Cones are pendulous and cylindrical; wild-type Seed Cones are broad and ellipsoidal in shape. The teratological structures consisted of a basal region that resembled a typical fertile Seed cone, and an apical proliferation that terminated in a well-developed pollen cone, resulting in a ‘bisexual’ unit. The proximal Seed cone and the distal pollen cone were separated by a sterile region that represents an elongation of the cone axis. Of a total of 14 anomalous bisexual units investigated, all had the same bauplan. Such an arrangement of basal ovulate and distal staminate reproductive structures in a teratological conifer cone has previously not been reported for Wollemia . This topology is 'inside-out' with respect to most other reported anomalous bisexual conifer Cones, which possess proximal staminate and distal ovulate structures. We discuss these spontaneous abnormalities in the broader context of understanding the homologies of Seed-plant reproductive structures. The patterning of conifer Cones is apparently highly labile, perhaps related to the extended cone axis and relatively long developmental duration.
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understanding the cone scale in cupressaceae insights from Seed cone teratology in glyptostrobus pensilis
PeerJ, 2018Co-Authors: Veit Martin Dorken, Paula J RudallAbstract:Both wild-type and teratological Seed Cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical Seed Cones bears two descending accessory shoots, interpreted here as Seed scales (ovuliferous scales). The primary Seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary Seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type Seed Cones, the fertile Seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological Seed Cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower Seed scale is here interpreted as the axis of the fertile Seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile Seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile Seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding Seed-cone homologies among extant conifers.
P B Tomlinson - One of the best experts on this subject based on the ideXlab platform.
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rescuing robert brown the origins of angio ovuly in Seed Cones of conifers
Botanical Review, 2012Co-Authors: P B TomlinsonAbstract:Robert Brown (1827) recognized the distinction between the two major classes of Seed plants on the basis, respectively, of exposed ovules, which receive pollen directly, and enclosed ovules, which do not, at the time of pollination. The two groups, unfortunately, became known as “Gymnosperms” and “Angiosperms”, a distinction not made by Brown. The names are, at best, useful only as identifying labels. As is established here, gymno-ovuly and angio-ovuly would have been better words and should serve as the most consistent distinguishing character among groups of Seed plants. Although conifers can hardly be claimed to be members of any lineage that led to the Angiosperms, the gymno-ovulate method of reproduction must have occurred in the direct ancestors of flowering plants. Interpolating development and functional evidence serves to resurrect Robert Brown’s important but neglected observation and correct misstatements implied in generally accepted systematic terminology. The result of this approach is to discover that the conifers in their reproductive diversity show some trends indicative of those characters that define the flowering plants. Although non-homologous these character manifestations provide useful models which can lead to a better understanding of the origin of “Angiosperms” from “Gymnosperms.” In the complex and extended process of reproductive development in both major groups regular transpositions occur, depending on whether “gymno-”and “angio-”are applied to ovules or Seeds. Gymno-ovuly and angio-spermy are the most common conditions in conifers but result in intrinsically opposed processes of pollen reception and subsequent Seed protection, which are resolved by successive changes in Seed-cone structure. The modern conifers illustrate considerable diversity of ovulate and Seed cone structure in relation to several biological functions, including traits that anticipate the angio-ovulate condition, in cone inception, ovule enclosure, pollen and embryo development and Seed dispersal. From the paleobotanical record we do have a good grasp of the structural changes in the progressive modification of the coniferous Seed cone in conifers, starting with the antecedent Carboniferous Cordaitales. These changes have involved the progressive condensation of a lax, branched strobilus and end with the highly condensed uniovulate “cone” as in many Podocarpus species in which the equivalent of a bitegmic ovule exists. The progressive changes can be perceived typologically among existing conifers but need to be understood as the result of biological processes that suggest increased reproductive efficiency, and can be added to our present quite robust understanding of conifer phylogeny.
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Seed cone and ovule ontogeny in metasequoia sequoia and sequoiadendron taxodiaceae coniferales
Botanical Journal of the Linnean Society, 1992Co-Authors: Tokushiro Takaso, P B TomlinsonAbstract:TAKASO, T. & TOMUNSON, P. B., 1992. Seed cone and ovule ontogeny in Metasequoia, Sequoia and Sequoiadendron (Taxodiaceae–Coniferales). Structural features of Seed Cones, up to the initiation of ovules, are developed in the three genera in the summer and late fall prior to pollination in the following spring, when Cones renew their further development. Bracts are initiated in a decussate manner in Metasequoia but spirally in Sequoia and Sequoiadendron. No ovuliferous scale is initiated, at most there is a shallow mound of tissue on the adaxial surface of the bract from which the ovules are developed. Metasequoia produces a single series of up to eight ovules in acropetal (centripetal order), Sequoia and Sequoiadendron produce a double series of six to nine ovules, also in acropetal order, since a second series of ovules appear distal to and alternate with the first series. Common features that unite the genera are the somewhat peltate configuration of the cone scales due to late intercalary expansion, the derivation of the vascular supply to the bract-ovule complex from a single bundle and the usual inversion of the Seed during late development, to which can be added developmental features. The absence of tooth-like structures, present in some other Taxodiaceae, is discussed in relation to cone evolution in the family being determined by changes in developmental timing. Emphasis is made on the way in which features of morphogenesis, determine cone organization in the three genera independent of an interpretation that relies solely on hypothetical ancestral forms.
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cone and ovule development in sciadopitys taxodiaceae coniferales
American Journal of Botany, 1991Co-Authors: Tokushiro Takaso, P B TomlinsonAbstract:Ontogeny of Seed Cones of Sciadopitys, with special reference to the ovule-supporting structure, is studied in material collected in Japan and Massachusetts. Cones are initiated as lateral or terminal structures in summer and complete the formation of most organs before winter. Bract development is well advanced before ovule-supporting structures are initiated. Continued cone development involves the formation of a narrow ridge of tissue in the axil of each fertile bract. This ridge develops a series of nine (but up to 12) apical lobes in centrifugal order, each of which is the primordium of a future tooth on the ovuliferous scale. Ovules are initiated as outgrowths of the adaxial surface of each lobe so that there is a one-to-one ratio between lobes and ovules. Intercalary extension of the ovuliferous scale itself (distally) and the common base of the bract and ovuliferous scale (proximally) greatly extends the complex. The ovuliferous scale eventually exceeds the subtending bract and its apex becomes recurved. Bracts each have a single trace, but each ovuliferous scale has a pair of traces that proliferate distally to irrigate ovule and scale lobe. Intercalary growth results in recurvature of the ovule trace. The organization of the cone is directly comparable with certain Permian fossils. Sciadopitys also seems unique within the Taxodiaceae in its centrifugal development of the ovule-supporting complex.
Suting Ding - One of the best experts on this subject based on the ideXlab platform.
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Seed Cones of tsuga pinaceae from the upper miocene of eastern china biogeographic and paleoclimatic implications
Review of Palaeobotany and Palynology, 2021Co-Authors: Suting Ding, Deliang Tang, Shuyang Chen, Bainian SunAbstract:Abstract Six well-preserved Seed Cones of Tsuga with fine bract-scale complexes were discovered from the late Miocene (Tortonian; 9.2–10.8 Ma) deposits of the Shengxian Formation at the border of Ninghai and Tiantai County, Zhejiang Province, eastern China. The fossil Cones possess ovate to elliptic shape, spirally arranged and obovate-orbicular ovuliferous scales, and cuneate-rhombic bracts hidden behind the scales with 2-lobed apex. Based on detailed comparison with extant and fossil Cones of Tsuga, the present fossils are assigned to Tsuga cf. dumosa (D. Don) Eichler. The discovery of the fossil Cones indicate that Tsuga had a wider distribution during the late Miocene than at the present. The increase of the difference in temperature between the coldest and warmest months since the late Miocene had forced Tsuga to retreat from eastern Zhejiang.
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needles and Seed Cones of pinus premassoniana sp nov and associated pollen cone from the upper miocene in east china
Review of Palaeobotany and Palynology, 2013Co-Authors: Suting Ding, Junlin Chen, Yi Yang, Defei Yan, Bainian SunAbstract:A long shoot with needles and two immature Seed Cones, and some isolated organs of shoot, needles and Seed Cones from the late Miocene Shengxian Formation in Zhejiang Province, East China are described. A detailed comparison of the gross morphology and cuticle micromorphology of needles and Seed Cones with previously published Cenozoic fossils and related extant pine species reveals that the present fossils can be identified as a new species, Pinus premassoniana sp. nov., which has the closest affinity with extant Pinus massoniana. A pollen cone with copious bisaccate pollen grains from the same locality is identified as an indeterminate species of subgenus Pinus. The pollen grains show a verrucate external sculpture on the corpus and sacci and an alveolae internal structure in the sacci. The fossil needle cuticles and pollen cone of the genus Pinus from China are reported for the first time. The modern distribution indicates that P. premassoniana sp. nov. should also live under a warm and humid climate. Hitherto, there is no any reliable fossil record that has an affinity with the extant P. massoniana. The occurrence of the present fossils suggests that P. premassoniana has existed in East China since at least in the late Miocene.
Bainian Sun - One of the best experts on this subject based on the ideXlab platform.
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Seed Cones of tsuga pinaceae from the upper miocene of eastern china biogeographic and paleoclimatic implications
Review of Palaeobotany and Palynology, 2021Co-Authors: Suting Ding, Deliang Tang, Shuyang Chen, Bainian SunAbstract:Abstract Six well-preserved Seed Cones of Tsuga with fine bract-scale complexes were discovered from the late Miocene (Tortonian; 9.2–10.8 Ma) deposits of the Shengxian Formation at the border of Ninghai and Tiantai County, Zhejiang Province, eastern China. The fossil Cones possess ovate to elliptic shape, spirally arranged and obovate-orbicular ovuliferous scales, and cuneate-rhombic bracts hidden behind the scales with 2-lobed apex. Based on detailed comparison with extant and fossil Cones of Tsuga, the present fossils are assigned to Tsuga cf. dumosa (D. Don) Eichler. The discovery of the fossil Cones indicate that Tsuga had a wider distribution during the late Miocene than at the present. The increase of the difference in temperature between the coldest and warmest months since the late Miocene had forced Tsuga to retreat from eastern Zhejiang.
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needles and Seed Cones of pinus premassoniana sp nov and associated pollen cone from the upper miocene in east china
Review of Palaeobotany and Palynology, 2013Co-Authors: Suting Ding, Junlin Chen, Yi Yang, Defei Yan, Bainian SunAbstract:A long shoot with needles and two immature Seed Cones, and some isolated organs of shoot, needles and Seed Cones from the late Miocene Shengxian Formation in Zhejiang Province, East China are described. A detailed comparison of the gross morphology and cuticle micromorphology of needles and Seed Cones with previously published Cenozoic fossils and related extant pine species reveals that the present fossils can be identified as a new species, Pinus premassoniana sp. nov., which has the closest affinity with extant Pinus massoniana. A pollen cone with copious bisaccate pollen grains from the same locality is identified as an indeterminate species of subgenus Pinus. The pollen grains show a verrucate external sculpture on the corpus and sacci and an alveolae internal structure in the sacci. The fossil needle cuticles and pollen cone of the genus Pinus from China are reported for the first time. The modern distribution indicates that P. premassoniana sp. nov. should also live under a warm and humid climate. Hitherto, there is no any reliable fossil record that has an affinity with the extant P. massoniana. The occurrence of the present fossils suggests that P. premassoniana has existed in East China since at least in the late Miocene.
Tatsuaki Kimura - One of the best experts on this subject based on the ideXlab platform.
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permineralized taxodiaceous Seed Cones from the upper cretaceous of hokkaido japan
Review of Palaeobotany and Palynology, 1993Co-Authors: Kenichi Saiki, Tatsuaki KimuraAbstract:Abstract A new taxodiaceous fossil genus, Mikasastrobus hokkaidoensis gen. et sp. nov. is described on the basis of six permineralized Seed Cones and a leafy shoot collected from the Upper Cretaceous (Coniacian-Santonian) of Hokkaido, Japan. The peel technique was applied for the anatomical observations. The fossil cone is terminal on a leafy shoot, ovoid in shape. 3–4 cm long and up to 2–3.5 cm in diameter, consisting of an axis and numerous cone scale complexes arranged helically around the axis. The complex is flattened and consists of an expanded apical half and stalk-like basal half. Each complex subtends a small-sized ovuliferous scale with 4–5 inverted ovules on its adaxial side. The serial sections show that each complex receives a single strand from the axis which later divides into many strands. Despite the presence of an ovuliferous scale tip, like that of Cunninghamia , the present fossil cone are most similar to Taiwania in their arrangement of strands.