Pollen Organs Research Articles

A new Harrisiothecium pollen organ from the Upper Triassic of South Central China

Extinct Mesozoic seed plants are key for understanding the evolution and relationships of seed plants, including homologies among their reproductive organs. Recent discoveries of exceptionally well-preserved fossils have greatly enhanced knowledge of the ovulate reproductive organs of Mesozoic seed plants, but research on the corresponding pollen organs is more limited. Here we describe a new species of Mesozoic pollen organ, Harrisiothecium sanduense sp. nov. based on material from the Upper Triassic Yangmeilong Formation in Hunan, South Central China. Harrisiothecium sanduense consists of a thick central axis bearing lateral secondary branches arranged mainly in a single plane and almost distichous. The lateral branches are unbranched or bifurcate, and bear one or two terminal capsules each consisting of two valves on either side of a median hinge. Each valve bears a row of six to seven elongated pollen sacs on the inner face. Harrisiothecium sanduense is similar to Harrisiothecium marsilioides from the Upper Triassic of Greenland and Hydropterangium roesleri, which we transfer to Harrisiothecium roesleri comb. nov., from the Upper Triassic of Germany, and like both species is also associated with pinnate leaves of the seed fern Ptilozamites. Harrisiothecium sanduense differs from Harrisiothecium marsilioides and Harrisiothecium roesleri in its more flattened structure with lateral branches that bear no more than one or two capsules. Harrisiothecium shares similarities to Pramelreuthia dubia, Pteroma, Pteruchus, Antevsia and Townrovia, as well as the structures that bear the pollen sacs in Bennettitales.

In search of the correspondence between in situ and dispersed pollen

The amount of information about the diversity of dispersed pollen grains and spores exceeds that about their in situ counterparts by several orders of magnitude. Strangely, there are several finds of in situ pollen types that are thus far unknown from dispersed palynomorph assemblages. Here we provide a brief discussion of this peculiar phenomenon based mainly on two examples from our recent studies, including a late Permian lyginopterid seed fern from Jordan and a Middle Jurassic conifer from Siberia. Several reasons could account for such “in situ only” pollen types, including the scarcity of the parent plants, low pollen productivity, entomophily, or immaturity of in situ pollen, although the last variant seems overestimated. Such pollen grains, when found dispersed, might also be considered as untypical, featureless or inadequately preserved specimens and, as a consequence, be reported without illustrations as undetermined specimens or even ignored altogether; this way, they receive little attention from the authors, remain unregistered, and cannot be analyzed by subsequent researchers. We stress the importance of publication of as complete as possible information about all components of palynological assemblages, including their photos, even if they do not belong to stratigraphically important taxa. We do not attribute the disparity to taphonomic differences between megafossil and microfossil deposition, because the ‘in situ only’ pollen types are absent not only in the same beds where the pollen organs were found, but are unknown from any other deposits.

Systematic Problems of Pollen Organs of the Genus Permotheca Zalessky from the Permian of Subangara

Systematic Problems of Pollen Organs of the Genus Permotheca Zalessky from the Permian of Subangara

Reconstructing the Tetrastichia bupatides Gordon plant; a Devonian–Mississippian hydrasperman gymnosperm from Oxroad Bay, Scotland and Ballyheigue, Ireland

An organismal concept for the Late Devonian/Mississippian hydrasperman seed fern Tetrastichia bupatides is developed from specimens collected at Oxroad Bay, East Lothian Scotland and Ballyheigue, County Kerry, Ireland. Specimens include interconnected fragments of stems, frond rachides, pinnae, pinnules, roots, pollen organs with enclosed pre-pollen, and cupules, as well as dispersed ovules. Both morphological and anatomical features are documented. The plant produces an unbranched, upright stem with a branched taproot, and small adventitious roots at the base of the stem. Stems have a mesarch actinostele with sympodial protoxylem architecture. Phyllotaxis ranges from helical to opposite/decussate, with planar fronds that typically fork twice at the base, and then produce pinnules of the Rhodea-type. Compact aggregate pollen organs are attached distally on secondary rachides and are constructed of cruciately forking axes that terminate in inverted, round, simple synangia of six elongated microsporangia attached to a basal pad of tissue. Ovulate cupules of the Calathospermum fimbriatum type are attached at the base of the frond. Ovules possibly could be Salpingostoma dasu or Eospermum oxroadense. Tetrastichia bupatides is now one of the most completely reconstructed of all Devonian-Mississippian hydrasperman seed ferns, and the most ancient gymnosperm for which the pattern of rooting has been established. The occurrence of a taproot at the base of the stem suggests that the plant may exhibit bipolar growth derived from a cotyledonary embryo.

A lyginopterid pollen organ from the upper Permian of the Dead Sea region

Here we report a pollen organ from the upper Permian of the Dead Sea region with in situ pollen showing a wall structure typical for lyginopterid seed ferns. The single specimen resembles the dispersed seed-fern pollen organs Dictyothalamus and Melissiotheca in being composed of numerous densely positioned, radiating pollen sacs that together form a characteristic honeycomb-like surface pattern. The small, rounded to oval, non-saccate cryptaperturate in situ pollen grains have a verrucate sculpture and show an alveolate wall ultrastructure with alveoli arranged in several tiers. The lyginopterids, a group of seed ferns, first appeared in the latest Devonian and were very widespread across Euramerica during the Mississippian. The group shows a clear demise in the middle and late Pennsylvanian. The youngest representatives have been reported from late Permian peat-swamps in Cathaysia. The morphology of the pollen organ, the ultrastructure of the pollen, and associated foliage present further evidence that lyginopterid seed ferns persisted until the late Permian and demonstrate that they were not restricted to peat-forming swamp environments, but that they were able to survive in drier environments.

Contributions towards whole-plant reconstructions of Dicroidium plants (Umkomasiaceae) from the Permian of Jordan

Four Dicroidium species and associated fertile organs are here described from the late Permian Umm Irna Formation (Dead Sea Region, Jordan). Dicroidium irnense, D. jordanense and D. robustum, which were so far only known from the Wadi Himara locality, are now reported from several other sites, some yielding nearly complete fronds and excellently preserved cuticles; D. hughesii, a species so far only known from the Triassic, is here reported from the upper Permian. The largest species, D. robustum emend. nov., can be correlated with the pollen organ Pteruchus lepidus sp. nov. and the cupulate structure Umkomasia aequatorialis sp. nov. based on repeated co-occurrences and striking similarities in cuticular features. Dicroidium irnense is associated with Pteruchus frenguellii sp. nov. based on consistent co-occurrence. Dispersed Umkomasia seeds are common in all localities where Dicroidium occurs. The here described material comprises some of the most completely reconstructed species of Umkomasiaceae known to date. All Dicroidium plants are characterized by comparatively large fronds and both Pteruchus species have strongly elongate, strap-shaped microsporophylls, similar to Triassic Umkomasiaceae growing under comparable, seasonally dry conditions. Dicroidium first appeared during the late Permian in the paleotropical regions, survived the end-Permian biotic crisis, colonized large parts of Gondwana during the Triassic, and persisted in southern high-latitude refugia into the Jurassic. Umkomasiaceae thus show a remarkable resilience as the group survived two of the most severe mass extinctions in Earth history.

Integrative Paleobotany: Affirming the Role of Fossils in Modern Plant Biology—Introduction and Dedication

Integrative Paleobotany: Affirming the Role of Fossils in Modern Plant Biology—Introduction and Dedication

The morphology and ultrastructure of Jurassic in situ ginkgoalean pollen

A fragmentary pollen organ with four to six microsporangia is discovered from the Middle Jurassic of the Irkutsk coal basin, Siberia. The in situ pollen grains are boat-shaped, monosulcate, and with a nearly psilate surface. The non-aperture ectexine is composed of a thick solid tectum, a thin infratectum, and a thin foot layer. The infratectum includes one row of small rare alveolae. The supposedly poorly preserved endexine is thin and grainy. The ectexine reduces greatly in the aperture area, where only homogeneous ectexinal patches are present over the endexine. The pollen grains under study resemble in their exine ultrastructure pollen grains of the modern Ginkgo biloba and pollen grains from dispersed seeds of a presumably ginkgoalean affinity from the Middle Jurassic of Uzbekistan. This suggests that the ginkgoalean exine ultrastructure of the modern type existed as early as the Middle Jurassic. The exine ultrastructure under study is also similar, though to lesser degree, to that of dispersed pollen grains of a presumed ginkgoalean affinity from the Cretaceous of the Russian Far East. The diversity of such a long-living group as ginkgoaleans is apparently reflected in the diversity of their exine ultrastructure. To the present knowledge, ginkgoalean pollen grains can be differentiated from similar boat-shaped monosulcate pollens by the following co-occurring characters: a thick homogeneous tectum, a thin infratectum with one row of structural elements, a thin foot layer, and an ectexine that is reduced in the aperture region to patches.

A new seed plant with multi-ovulate cupules from the Upper Devonian of South China

The Late Devonian (Famennian) witnessed the diversification of early seed plants (spermatophytes), which usually possess cupulate ovules as their female reproductive organs. Previous studies have described two such plants with uni-ovulate cupules from South China. Here, a new seed plant, Calycosperma qii gen. et sp. nov., is reported from the Upper Devonian Wutong Formation of Changxing County, Zhejiang Province, China, exemplifying the first occurrence of multi-ovulate cupules in South China and eastern Asia. This plant shows cupulate ovules and associated synangiate pollen organs. Cupules are goblet-shaped with the basal two-third fused and the distal one-third dissected into 16 linear tips. Each cupule bears two ovules at the bottom, below the bases of linear tips. Synangiate pollen organs terminate isotomously divided fertile branches and consist of three to six basally fused elongate microsporangia. The considerably fused cupule of Calycosperma suggests an earlier differentiation of multi-ovulate cupules in Famennian. Calycosperma shows the largest cupules among the known Devonian seed plants, which are inferred to provide greater protection to ovules and possibly imply a hydrochoric reproduction strategy for this plant.

Revision of Fedekurtzia (pteridosperm) and allied fronds from the Carboniferous of Gondwana

AbstractCarboniferous foliage ofFedekurtzia argentina(Kurtz) Archangelsky from Gondwana is systematically described and revised. The frond is reconstructed based on specimens of the late Serpukhovian–BashkirianNothorhacopteris/Botrychiopsis/Ginkgophyllumflora of western Argentina, especially from the Jejenes, Tupe and Volcán formations. The whole-frond reconstruction emphasizes the variation in pinnule shape throughout the basal, medial and distal sections of the frond. The basalmost rachis possesses cyclopteroid pinnules grading to pinnae with obovate to wedge-shaped pinnules at the medial section of the frond. Distal pinnae are shorter, bearing imbricate and more dissected pinnules. Specimens from the same type locality from whichF. argentinacomes, previously assigned toTriphyllopteris cuyanaLeguizamón & Vega, are reassigned toF. argentina, as well as ovuliferous and microsporangiate structures in organic connection. Two decades ago a revision of the GermanTriphyllopterisgenus rejectedT. cuyanaas representative of the taxon, and the Argentinian specimens remained as indeterminate “triphyllopteroid” fronds. The ovulate organPolycalyxVega & Archangelsky is considered to be in organic connection with vegetative fragments ofF. argentina, and its cupulate character is discussed. Pollen organs represented by multi-forked axes bearing fusiform sporangia ofRinconadiaVega are also in organic attachment and included in theFedekurtzia argentinareconstruction. The pollen or prepollen grains are trilete and with granulate sculpture. The paper presents a comparison withBotrychiopsis weissianaKurtz emend. Archangelsky & Arrondo, which differs in its rounded and entire-margin pinnules. Similar specimens from Australia formerly described asRhacopteris,SphenopteridiumandArchaeopterisand currently included inFedekurtzia intermediaRigby share morphological characters with the Argentinian species. A revision of the Australian material is necessary to confirm synonymy.Fedekurtziabelongs to the pteridosperms based on the reproductive organs and is here assigned to Austrocalyxaceae. Its reconstruction now constitutes one of the most complete seed-ferns known from the Carboniferous of Gondwana.

Proteomes and Phosphoproteomes of Anther and Pollen: Availability and Progress.

In flowering plants, anther development plays crucial role in sexual reproduction. Within the anther, microspore mother cells meiosis produces microspores, which further develop into pollen grains that play decisive role in plant reproduction. Previous studies on anther biology mainly focused on single gene functions relying on genetic and molecular methods. Recently, anther development has been expanded from multiple OMICS approaches like transcriptomics, proteomics/phosphoproteomics, and metabolomics. The development of proteomics techniques allowing increased proteome coverage and quantitative measurements of proteins which can characterize proteomes and their modulation during normal development, biotic and abiotic stresses in anther development. In this review, we summarize the achievements of proteomics and phosphoproteomics with anther and pollen organs from model plant and crop species (i.e. Arabidopsis, rice, tobacco). The increased proteomic information facilitated translation of information from the models to crops and thus aid in agricultural improvement.

Further study of Late Devonian seed plant Cosmosperma polyloba: its reconstruction and evolutionary significance

BackgroundThe earliest seed plants in the Late Devonian (Famennian) are abundant and well known. However, most of them lack information regarding the frond system and reconstruction. Cosmosperma polyloba represents the first Devonian ovule in China and East Asia, and its cupules, isolated synangiate pollen organs and pinnules have been studied in the preceding years.ResultsNew fossils of Cosmosperma were obtained from the type locality, i.e. the Leigutai Member of the Wutong Formation in Fanwan Village, Changxing County, Zhejiang Province, South China. The collection illustrates stems and fronds extensively covered in prickles, as well as fertile portions including uniovulate cupules and anisotomous branches bearing synangiate pollen organs. The stems are unbranched and bear fronds helically. Fronds are dimorphic, displaying bifurcate and trifurcate types, with the latter possibly connected to fertile rachises terminated by pollen organs. Tertiary and quaternary rachises possessing pinnules are arranged alternately (pinnately). The cupule is uniovulate and the ovule has four linear integumentary lobes fused in basal 1/3. The striations on the stems and rachises may indicate a Sparganum-type cortex.ConclusionsCosmosperma further demonstrates diversification of frond branching patterns in the earliest seed plants. The less-fused cupule and integument of this plant are considered primitive among Devonian spermatophytes with uniovulate cupules. We tentatively reconstructed Cosmosperma with an upright, semi-self-supporting habit, and the prickles along stems and frond rachises were interpreted as characteristics facilitating supporting rather than defensive structures.

Lunzia austriaca – a bennettitalean microsporangiate structure with Cycadopites-like in situ pollen from the Carnian (Upper Triassic) of Lunz, Austria

Based on new evidence obtained from freshly collected fossils, we here provide an emendation of Lunzia and Lunzia austriaca with an updated interpretation of the organ architecture, function and affiliation. The specimens reveal that Lunzia austriaca is a pollen organ resembling structures assigned to Weltrichia. Lunzia austriaca comprises cup-shaped pollen organs that develop up to about ten, basally fused lobes carrying appendices. The appendices are arranged pairwise and inserted laterally to a rachis-like structure, in a pinnate architecture on their adaxial side and are interpreted as prominent segments or fertile pinnae that bear numerous synangia identifying them as microsporophylls. The nature of the rachis-like structure is not straightforward. The rachis-like structure could either be fused with a bract – this fused structure then constituting the lobes – or itself been modified depicting a foliate appearance. The microsporophylls are narrow at the base and involute apically or with a sterile apical cowl. Numerous synangia with contracted bases are arranged on the inner (adaxial) side of the microsporophylls in long rows. The synangia consist of presumably four pollen sacs (microsporangia), are oblong and dehisce longitudinally. The pollen is monosulcate, elliptical and with a smooth exine (psilate). It is identified as Monocolpopollenites (=Cycadopites); from the size range, it fits best into Cycadopites accerimus. The architecture and the epidermal anatomy of Lunzia austriaca is discussed and its structure is compared with several contemporary bennettitaleans; sterile foliage and ovulate structures most likely associated with Lunzia austriaca are Pterophyllum filicoides and Westersheimia pramelreuthensis, respectively.

A New Species ofGinkgowith Male Cones and Pollen Grains in situ from the Middle Jurassic of Eastern Xinjiang, China

Well-preserved Ginkgo pollen organs are analyzed from the Middle Jurassic Xishanyao Formation of the Turpan-Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China, and are described as a new species, Ginkgo hamiensis Z.X. Wang et B.N. Sun sp. nov. The immature male cones are cylindrical and catkin-like, with two longitudinal stripes on the stalk. The pollen sacs are shaped like a long oval with two pollen sacs fused together for each microsporophyll, and the microsporophyll tip is a triangular cystidium. The pollen grains are oblong or fusiform and monocolpate; both ends are blunt or sharp. By comparison with previously reported fossil records of Ginkgo plants, we determined that the current fossils are different from all other reported species; thus, the present fossil is referred to as a new species of Ginkgo. The reproductive organs of the Ginkgo fossils described herein can provide valuable information for the study of Ginkgo plants. Further, there are two probable evolutionary trends in the Ginkgo pollen cones. One trend is that the number of pollen sacs changed from three or four during the Jurassic and Cretaceous to two at the present day; the other is that the number of pollen sacs has remained two from the Middle Jurassic to the present day. In addition, the pollen cones described herein are similar to the pollen cones of the extant Ginkgo, which strongly indicates that the morphology of Ginkgo plants may have remained highly conserved over millions of years.

A new Pennsylvanian pollen organ from northwestern Missouri with affinities in the Lyginopteridales

An Upper Pennsylvanian locality (Bonner Springs Shale, Kansas City Group, Middle Missourian) in western Missouri contains a diverse and well-preserved fossil assemblage of both plants and arthropods. The plants are preserved as impressions and compressions, and include fertile and vegetative remains of various sphenopsids, lycopsids, ferns, seed ferns, cordaites and conifers. The discovery of a branching system with lyginopterid pollen organs, Parkvillia northcuttii, demonstrates that this group of Paleozoic seed ferns was more diverse and complex than previously known. The fertile structure is characterized by multiple levels of branching with the penultimate branches alternately arranged; ultimate rachises bearing 6–10 alternately arranged, slightly flattened, shield-shaped synangia. Synangia are approximately 5mm in diameter and each consists of a cap with up to 18 sporangia attached to the abaxial surface. The radial and trilete pollen is ornamented by grana and coni. Also in the assemblage are small radially symmetrical ovules and sphenopterid foliage, suggesting that this assemblage contains multiple lyginopterid taxa. The orientation of sporangia and features of the synangia, together with the three-dimensional branching, indicate a morphological pattern that has not been recognized within the Lyginopteridaceae.

Pollen Organ Telangiopsis sp. of Late Devonian Seed Plant and Associated Vegetative Frond

Pollen organ Telangiopsis sp., associated with but not attached to vegetative fronds, has been collected from the Upper Devonian (Famennian) Wutong Formation, Dongzhi County, Anhui Province, China. Fertile axes with terminal pollen organs are dichotomous for 2–4 times and may be proximally attached by fragmentary pinnules. Pollen organs are synangiate and borne on the top of a short stalk. Synangia are radial in symmetry and each consists of 4–8 elongate microsporangia fused at base. Microsporangia have a longitudinal dehiscence line and show a tapered apex. The associated stem is spiny and bears a vegetative frond which bifurcates once at the basalmost part. Frond rachises possess one order of pinna arranged alternately. Pinnules are borne alternately, planate, highly dissected, and equally dichotomous for 2–3 times. Comparisons among Late Devonian seed plants recognize several branching patterns in the fertile fronds/axes bearing terminal pollen organs. Telangiopsis sp. reinforces that the Late Devonian pollen organs are synangiate usually with basally fused microsporangia. It is suggested that the evolutionary divergence of radial and bilateral symmetries of pollen organs may have occurred in the Famennian, when the earliest seed plants evolved planate and sometimes laminate pinnules.

A Late Devonian fertile organ with seed plant affinities from China.

Seed plants underwent first major evolutionary radiation in the Late Devonian (Famennian), as evidenced by the numerous ovules described to date. However, the early pollen organs are underrepresented, so that their structure and evolution remain poorly known. Here we report a new taxon of pollen organ Placotheca minuta from the Late Devonian. The synangium consists of many basally and more or less laterally fused microsporangia borne on the margin of a pad. The prepollen is spherical and trilete. The appearance of Famennian synangia especially in Placotheca does not support the current understanding that the earliest pollen organs closely resembled the fructifications of the ancestral progymnosperms. Placotheca indicates earlier diversification of pollen organs than previously expected and is highly derived among the early pollen organs with trilete prepollen. It is suggested that, immediately after the origination of seed plants, pollen organs had evolved at a rapid rate, whereas their prepollen remained primitively spore-like.

Exine ultrastructure of in situ Protohaploxypinus from a Permian peltasperm pollen organ, Russian Platform

The fine morphology and exine ultrastructure are studied in pollen grains of Protohaploxypinus-type, which were extracted from a pollen organ of Permotheca striatifera from the upper Permian (Lopingian) Isady locality (Vologda Region, Russia). The pollen grains are bisaccate and striate, with up to ten proximal ribs. The ectexine and endexine differ in ultrastructure and electron density. The ectexine is alveolate; the endexine is more electron-dense and appears homogeneous, though some indices of layering were observed under higher magnifications. The sacci appear protosaccate. Areas that flank the body are a diminished and more regular version of the sacci. In ribs, the ectexine includes an outer continuous layer, a thinner underlying alveolate layer, and an inner layer. Grooves between the ribs either retain the inner homogeneous ectexinal layer resting on the endexine or are lined by the endexine alone. The distal face of the body is covered by the endexine alone. The obtained data are compared with available ultrastructural information on pollen grains of the Protohaploxypinus-type of different origins and with that on other peltasperm pollen types such as Vittatina, Vesicaspora and Cycadopites. The diversity of species of Permotheca is outlined.

Cosmosperma polyloba gen. et sp. nov., a seed plant from the Upper Devonian of South China.

Seed plants with ovules were abundant in the Late Devonian of Euramerica and they contribute significantly to our understanding of their early history. However, coeval ovules have been scarce in other regions of the world. Specimens of the seed plant Cosmosperma polyloba gen. et sp. nov. Wang et al. were recently obtained from the Upper Devonian (Famennian) Wutong Formation, at Fanwan Village, Changxing County, Zhejiang Province, China. This new seed plant has cupulate ovules, the uniovulate cupules with up to 16 distal segments and with minute spines on the outer surface, synangiate pollen organs bearing six to eight microsporangia fused only at the base, and planate and highly dissected pinnules in alternate arrangement. It differs from other Devonian seed plants mainly in the organization and position of the uniovulate and ornamented cupule, and in the highly dissected pinnules. Cosmosperma Wang et al. represents the first Devonian ovules recovered from China or eastern Asia and further illustrates the diversity of early spermatophytes. As for the Late Devonian seed plants, it is suggested that the pollen organs are synangiate and simple in organization, and the branches and leaves are generally planate.

The fine morphology of pollen grains from the pollen chamber of a supposed ginkgoalean seed from the Middle Jurassic of Uzbekistan (Angren locality)

Pollen grains of Cycadopites-type were found in the pollen chamber of a supposed ginkgoalean seed Allicospermum sp. from the Middle Jurassic deposits of Uzbekistan (Angren locality). The pollen grains were studied with help of LM, CLSM, SEM, and TEM. All pollen grains show the identical morphology and exine ultrastructure allowing us to suppose the same botanical affinity. The pollen morphological data do not contradict the ginkgoalean interpretation of the seed; therefore, the pollen grains and the seed most probably did belong to the same parent plant. The pollen grains are monosulcate, the non-apertural surface is nearly psilate, with low short elements, which are occasionally scattered over the surface or more densely distributed. The aperture and adjacent areas appear to bear more distinct sculpturing. The ectexine is composed of a prominent solid tectum, a thin infratectum, and a thin foot layer. The infratectum is formed of one row of alveolae, which are more voluminous laterally, where the ultrastructure is more easily understandable. The endexine is multilamellate, although it is evident only in some regions of stained sections. Towards the aperture the ectexine becomes gradually thinner; over the aperture no sublayers can be discerned within the ectexine. The ectexine of the apertural region repeatedly varies in thickness, reflecting a sculpturing surface of this region. The obtained data contribute to the knowledge about the exine ultrastructure of ginkgoaleans; nonetheless, a TEM study of ginkgoalean pollen grains extracted from pollen organs is still highly desirable. We also considered pluses and minuses of CLSM: it failed to substitute SEM, since the surface pattern under study was too fine, but demonstrated the general morphology of the pollen grains under study better than conventional LM. The possibility of viewing virtual sections of any area of the pollen grain was profitable for later interpretation of TEM sections. CLSM would give better results in interpreting relatively large palynological objects with distinct sculptural elements, a complicated architecture, variously arranged appendages, or possessing cameras.