Exine Ultrastructure Research Articles

Comment on “The ‘seed-fern’ Lepidopteris mass-produced the abnormal pollen Ricciisporites during the end-Triassic biotic crisis” by V. Vajda, S. McLoughlin, S. M. Slater, O. Gustafsson, and A. G. Rasmusson [Palaeogeography, Palaeoclimatology, Palaeoecology, 627 (2023), 111,723

Recently, Ricciisporites Lundblad and Cycadopites Wodehouse (=Monosulcites Cookson) pollen types have been found cooccurring in Antevsia zeilleri (Nathorst) Harris pollen sacs and it was assumed that the tetrads of Ricciisporites resulted from atypical pollen developmental pathway in which the pollen grains failed to separate. The pollen grains of Cycadopites type were interpreted as normal pollen grains of a peltasperm with Antevsia zeilleri pollen sacs and Lepidopteris ottonis (Göppert) Schimper foliage, and Ricciisporites, as abnormal pollen tetrads of this parent plant. However, if it were true, the exines in the pollen grains of the two types should have something in common in the ultrastructure. Examples of aberrant pollen in living seed plants show that changes occurring in the predetermined succession of events of exine development are minor and even if they finally lead to a significantly altered mature exine, the original structural plan remains recognizable. Contrariwise, the two pollen types are too dissimilar by their exine ultrastructure as well as by the general morphology and exine sculpture. Comparison with ontogenetic data on suitable modern analogues also allows one to suppose that exines of Ricciisporites and Cycadopites developed differently, in unrelated parent plants. Another explanation should be found for the presence of Ricciisporites tetrads in these pollen sacs.

Palynotaxonomy of the subtribe Anisopappinae (Athroismeae, Asteraceae) and the genus Duhaldea (Inuleae, Asteraceae) based on their exine ultrastructure

The exine ultrastructure of 18 species of Anisopappus (Anisopappinae, Athroismeae, Asteraceae) and three species of Duhaldea (Inuleae, Asteraceae) was studied using transmission electron microscopy (TEM). Two ultrastructural patterns were identified: senecioid and helianthoid. The senecioid pattern is characteristic of the species included in the basal clades of the phylogenetic tree of Anisopappus, as published in earlier studies. The helianthoid pattern is restricted to the taxa placed in the derived clades, including the core group of species of Anisopappus in which A. chinensis, the type species, is included. The observed ultrastructural differences seem to suggest that a future splitting of Anisopappus into several different genera should not be disregarded and that the helianthoid pattern represents, within this genus, the derived condition. The ultrastructure of the exine supports the inclusion, suggested by previous authors, of the species Duhaldea stuhlmannii, but not that of Philyrophyllum schinzii, in Anisopappus. In contrast, the three studied species of Duhaldea (D. cappa, D. nervosa, D. revoluta) present an exine with a senecioid pattern, which is characteristic of the tribe Inuleae, in which they are included. The ectoaperture, mesoaperture, and endoaperture of all studied Anisopappinae and of Duhaldea respectively intersect the tectum plus columellae, the foot layer and the outer part of the endexine, and the inner part of the endexine. This feature seems to characterize, in a consistent way, the ‘Heliantheae alliance’, and is also present in all the studied Asteroideae (except Anthemideae), Dicomoideae, and Carduoideae.

Pollen grains associated with Karkenia irkutensis Nosova (Ginkgoales) from the Jurassic of Siberia

Pollen grains found on the nucellar cuticle and the outer cuticle of the integument of Karkenia irkutensis ovules from the Middle Jurassic of the Irkutsk Coal Basin in Siberia were studied with light and transmission electron microscopies. The overwhelming majority of the pollen grains are non-saccate, boat-shaped and monosulcate and can be ascribed to Cycadopites, which fits to what we expected to find in association with ginkgoalean macrofossils. In addition, several non-saccate and bisaccate pollen grains were also detected and interpreted as alien pollen of wind-pollinated conifers. The Cycadopites pollen grains showed from moderate to poor preservation of the exine ultrastructure, that restricted us from decisive conclusions. Differences in the exine ultrastructure among the sectioned Cycadopites pollen grains are probably due to the insufficient preservation and different angles under which the pollen grains were sectioned, and the Cycadopites pollen most probably derived from the same plant. The ectexine is more electron-dense and much thicker than the endexine, which is not always preserved. The ectexine is predominantly homogeneous, but rare cavities of irregular size and shape (=alveoli) are present in a row in the deep layers of the ectexine. Towards the aperture, the ectexine becomes thinner and can acquire a crenulate outer contour (that means a more distinct surface sculpturing). The exine is usually broken over the aperture. This set of characters is more similar to Ginkgo-type of the exine ultrastructure than to Aegianthus- and Sorosaccus sp.-types, which we defined for ginkgoaleans.

On the exine ultrastructure of fossil ginkgoaleans: In situ pollen of Sorosaccus Harris

The morphology and exine ultrastructure have been studied of pollen grains from pollen cones of Sorosaccus sibiricus Prynada from the Ust’-Baley (Aalenian, Siberia), Sorosaccus sp. from the Vladimirovka (Aalenian-Bajocian, Siberia), and S. ex gr. sibiricus Prynada from the Tyrma (Tithonian–Berriasian, Russian Far East) localities. The pollen grains are boat-shaped and monosulcate. A finely granulate pattern is discernible under high magnification of light microscope in pollen grains from Vladimirovka and Tyrma; SEM shows that this pattern is formed by flat verrucae. TEM shows that sculptural elements are present on the surface of pollen grains from Ust’-Baley, although it is not evident in LM and SEM. By previous data on modern and fossil members, we believed that ginkgoalean pollen grains can be differentiated from similar boat-shaped monosulcate pollen of other affinities by a ratio of ectexinal sublayers (a thick homogeneous tectum, a thin infratectum of one row of structural elements, and a thin foot layer) in combination with an ectexine that is greatly reduced in the aperture region. Freshly obtained data have revealed another set of characters, with a less prominent tectum by comparison to underlying sublayers, an infratectum with small granules within the alveoli, and a prominent verrucate surface pattern that is distinguishable even in transmitted light. Ginkgoaleans are characterized by more than one set of ultrastructural characters of the exine.

Pollen cones and in situ pollen of Aegianthus Krassilov from the Middle Jurassic of East Siberia, Russia

The paper documents in detail the morphological and epidermal characters of the pollen cones and in situ pollen of Aegianthus based on the study of specimens from the Prisayan Formation (Middle Jurassic) in the Irkutsk Basin (Siberia, Russia). An emended diagnosis is provided and a lectotype is selected for the type species, A. sibiricus, since a holotype/lectotype was not indicated in the previous publications of this species. Resin bodies are found in sporangiophores of A. sibiricus for the first time. The number of sporangia is specified as 10–12 per sporangiophore. This species differs from other Aegianthus species in smooth periclinal cell walls and lacking papillae on the subsidiary cells of the stomata in the abaxial epidermis of the peltate head. A new species, A. irkutensis, is described from the same Prisayan Formation of the Idan locality in the Irkutsk Basin. Unlike A. sibiricus, the cells of the outer epidermis of A. irkutensis are strongly papillate. A. irkutensis differs from other Aegianthus species by smaller resin bodies, numerous and longer sporangia. Pollen cones of both A. sibiricus and A. irkutensis were found in association with leaves of Sphenobaiera. The pollen of A. irkutensis are similar to those of A. sibiricus in morphology and ultrastructure. Pollen grains are boat-shaped, monosulcate. The exine surface is psilate or scabrate in the light microscope, and scabrate to granulate in SEM; the infratectum consists of large granules or columella-like elements. The exine ultrastructure of the Aegianthus pollen under study implies a ginkgoalean or gnetophytalean affinity.

Pollen morphology, ultrasculpture and ultrastructure of Poiretia Vent. (Leguminosae – Papilionoideae – Dalbergieae – Adesmia informal clade)

Pollen morphology, ultrasculpture and ultrastructure were investigated for Poiretia in search of morphological characters of taxonomic importance using light microscopy as well as scanning and transmission electron microscopy. Additionally, principal components analysis was done to elucidate patterns of variation among the species. Pollen grains are small to medium size, isopolar, prolate spheroidal to prolate, 3-zonocolporate, colporus with operculum, membrane and margo are ornamented. Five pollen types are recognised and described based on mesocolpium exine ultrasculpture. Exine consists of a compact tectum, eutectate, tectate perforate to semitectate, the infratectum is collumelar and granular, foot layer discontinuous to absent in aperture region and endexine is continuous. A comprehensive description of the operculum, membrane ornamentations and the ultrastructure of exine were given for all species in the genus, nine of which were not previously analysed palynologically. Systematic implications of the palynological variations found in the literature and through light, scanning and transmission electron microscopical analyses were discussed. This article describes the importance of the characterisation of Poiretia pollen grains, which contributes to the systematics of the Adesmia informal clade. The class of endoaperture, ultrasculpture of mesocolpium and apocolpium, and ultrastructure of tectum, foot layer, and endexine support the eurypalynous status of Poiretia and are useful to recognise some species that have problematic delimitation (P. latifolia, P. coriifolia, P. unifoliolata, P. mattogrossensis, P. elegans, P. marginata) as well as groups of species.

Three Aquilapollenites species from the late Maastrichtian of China: New data and comparisons

Three species, Aquilapollenites quadricretaceus, A. stelckii, and A. amicus, from the late Maastrichtian of China have been studied using light, scanning, and transmission electron microscopy. Rare specimens of Aquilapollenites quadricretaceus and A. stelckii with reduced polar and/or equatorial projections were observed. A. quadricretaceus and A. stelckii are more similar to each other in exine ultrastructure than they are to A. amicus, which has a thicker foot layer and thin infratectum. A comparison with extant Lythraceae pollen revealed characters similar to those of triprojectate pollen, probably resulting from convergent evolution: prolate pollen with protruding equatorial ora and pores, frequent occurrence of striate and reticulate exine sculpturing, consistent presence of endexine, and infratectal columellae that are mostly simple and not branched. The colporate condition is rare in Triprojectacites and occurs in species with rather short equatorial projections, which suggests that the protruding part of the pollen grain, corresponding to the equatorial projections seen in Triprojectacites, might have been replaced functionally by the ora in tricolporate pollen like that of extant angiosperms. The possible adaptation of some Triprojectacites species to a wetland environment is suggested based on comparison with extant pollen.

Northern Hemisphere megafossil of Dacrycarpus (Podocarpaceae) from the Miocene of South China and its evolutionary and paleoecological implications

AbstractThe modern genus Dacrycarpus (Endl.) de Laub. of the family Podocarpaceae, containing nine species, is mainly distributed in tropical mountain rainforests of the southwestern Pacific region, ranging from New Zealand to low‐latitude Asia. This genus has abundant fossil records in both hemispheres, but all the known megafossils were limited to Australasia and South America. Here we report on Dacrycarpus guipingensis sp. nov. from the Miocene Erzitang Formation of Guangxi, South China. This is the first megafossil of Dacrycarpus in the Northern Hemisphere. The new species is represented by mummified dimorphic foliage, ovuliferous shoots, and a male cone with in situ pollen. It resembles the extant Dacrycarpus imbricatus (Blume) de Laub., which is common in rainforests from southern China and northern Myanmar to Fiji. This paper presents the first data on the anatomical structure of seed cone and exine ultrastructure of Dacrycarpus in situ pollen grains from a fossil material by using computed tomography scanning and ultrathin sectioning. For comparative purpose, data on the pollen morphology and ultrastructure were obtained for modern D. imbricatus for the first time. The D. guipingensis fossils strongly suggest the Miocene arrival of Dacrycarpus in Asia from the Southern Hemisphere. Based on the modern ecological niche and related fossil elements, this fossil locality was probably covered by conifer–broad‐leaved mountain rainforests during the Miocene.

The exine ultrastructure of Pretricolpipollenites bharadwajii from the Permian of Jordan

Dispersed trisulcate pollen grains of Pretricolpipollenites bharadwajii from the ?latest Permian of Jordan were studied with light, scanning, and transmission electron microscopy. The three sulci are located on the disal side. The median sulcus is usually longer, wider than the other two sulci, and has rounded aperture ends. The exine sculpturing and aperture membrane are scabrate. The ectexine includes a thick tectum, granular infratectum, and thin foot layer. The endexine is lamellate. A comparison with the closest similar genus Eucommiidites suggests overlapping characters; though the position of the three sulci on the distal side in Pretricolpipollenites bharadwajii and sulci on different sides in Eucommiidites indicates a possible distinguishing feature. Studies of exine ultrastructure of the other two Pretricolpipollenites species are needed to support or discard the distinction of Pretricolpipollenites and Eucommiidites.

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.

Comparative study of pollen morphology and exine ultrastructure in tetrads, octads and polyads of the genus Mimosa (Leguminosae)

ABSTRACTThis is the first study of exine ultrastructure to be performed in five endemic Mexican Mimosa taxa (M. pringlei var. pringlei, M. calcicola, M. spirocarpa, M. caerulea and M. sousae), one occurring in Mexico and Central America (M. occidentalis), one widely distributed throughout the neotropics (M. setosa var. paludosa), and two in South America (M. irrigua and M. daleoides). Mimosa pollen grains are associated in polyads (12 grains), octads and tetrads. Polyads and octads in members of the basal clade of Mimosa phylogeny (sect. Mimadenia) evince the affinity of Mimosa with Piptadenia. Octads are retained in sect. Batocaulon and tetrads are evolved in this section. More recent clades (sect. Habbasia, Mimosa and Calothamnos) only show tetrads varying in size and shape. Polyads show greater variation in the exine layers, with a bistratified granular structure. Octads display a columellar-granular infratectal structure while tetrads in sect. Mimosa exhibit a less variable exine with a granular infratectal structure.

Palynotaxonomy of the genus Gladiopappus (Dicomeae, Asteraceae) with special emphasis on the exine ultrastructure and mesoapertures

The pollen morphology of Gladiopappus vernonioides was studied with transmission (TEM) and scanning (SEM) electron microscopy and with light microscopy (LM). An Anthemoid pattern of exine ultrastructure was found. The pollen morphology of Gladiopappus supports the inclusion of this genus in the tribe Dicomeae and subtribe Dicominae but not in the Mutisieae s.str. The apertural system of G. vernonioides includes a mesoaperture that intersects the foot layer and the upper layer of the endexine, a condition already pointed out for several tribes of Asteroideae (Helenieae, Gnaphaliinae, Heliantheae, Inuleae, Senecioneae) and Carduoideae (Cardueae, Dicomeae). It is suggested that the existence of an intermediate aperture could characterize the apertural system of the Asteraceae as a synapomorphy.

Pollen grains associated with gymnospermous mesofossils from the Jurassic of Uzbekistan

Pollen grains were studied which are associated with supposed ginkgoalean seeds and leaves from the Middle Jurassic locality of Angren in Uzbekistan. The fine morphology of the pollen grains was observed with the help of light, confocal laser scanning, scanning electron, and transmission electron microscopes. The morphology and ultrastructure of the pollen grains show that although some of them belong to ginkgoaleans, others belong to conifers and cycadaleans. Bisaccate conifer pollen grains were found in the pollen chambers of seeds of Allicospermum sp. and A. angrenicum. Non-saccate boat-shaped pollen grains that can be ascribed to the genus Cycadopites were found in association with a seed of Ginkgo gomolitzkyana, leaves of Sphenobaiera angrenica, and in pollen chambers of seeds of A. angrenicum. These Cycadopites pollen grains show several types of exine, which allowed us to draw conclusions about their botanical affinities. The Cycadopites pollen associated with a seed of Ginkgo gomolitzkyana shows a ginkgoalean exine ultrastructure. Of interest is that its ultrastructure shows some dissimilarities from that of pollen grains of the ginkgoalean morphology and ultrastructure, which were earlier studied from the pollen chamber of a seed of A. budantsevii from the same locality. We think on this basis that at least two members of the ginkgoaleans grew in the cenose. The Cycadopites pollen grains from leaves of S. angrenica and from pollen chambers of seeds of A. angrenicum show a cycadalean exine ultrastructure. In sum, the morphological studies revealed pollen grains of two members of ginkgoaleans associated with the ginkgoalean remains and pollen grains of conifers that are most probably alien to the enclosing seeds. As to the cycadalean pollen from the seeds of A. angrenicum, the seeds were either contaminated by cycad pollen or produced by a cycadalean parent plant rather than a ginkgoalean plant. The revealed pollen diversity is an argument to be more careful while reconstructing whole plants on the basis of such materials.

The metareticulate pollen morphology of Alternanthera Forssk. (Gomphrenoideae, Amaranthaceae) and its taxonomic implications

Alternanthera (Amaranthaceae) is a diverse genus largely restricted to the American Tropics that belongs to the alternantheroid clade containing C4 and C3–C4 intermediate species. This research focuses on the study of pollen characters by studying 13 species, representatives of the two major clades and subclades of Alternanthera. General palynological comparisons were conducted with light microscopy (LM), scanning electron microscopy (SEM) and with confocal laser scanning microscopy (CLSM) for exine ultrastructure. Twenty-five characters were measured and described for Alternanthera and among these, 14 pollen characters were used to discriminate pollen groups using cluster analysis and canonical analysis of principal coordinates (CAP). Pollen form and ornamentation, pores number, spines length, number of ektexinous bodies and nanospines on the ektexinous bodies on pore membranes, arrangement of nanopores and spines on structural elements, and metareticula form were taxonomically important and therefore used to construct the first palynological key to the alternantheroid clade species. Our study indicates that the seemingly subtle morphological variation of pollen is useful for recognising three main pollen types within Alternanthera. The much needed palynological terminology for describing the mesoporium in the metareticulate pollen of Amaranthaceae is provided.

Exine ultrastructure of in situ pollen from the cycadalean cone Androstrobus manis Harris, 1941 from the Jurassic of England

Pollen grains extracted from the cycad pollen cone Androstrobus manis Harris, 1941 from the Bajocian of Yorkshire were studied by means of LM, SEM and TEM. Boat-shaped pollen grains of Cycadopites-type were found, with a distinct sulcus and a typically cycadalean foveolate-fossulate surface. The exine is two-layered, with a more electron-dense endexine. The tectum is continuous. There is no distinct boundary between the tectum and infratectum. The infratectum is alveolate, with numerous, irregularly distributed rounded alveolae in the majority of the sections. Occasionally, rounded alveolae are organized in several rows. Even more rarely, elongated alveolae are arranged perpendicular to the surface of the exine. Such a variable ectexine appearance has been already described in modern cycads and was explained by not strictly perpendicular orientation of pollen walls towards the plane of the sections. Distally, the exine becomes thinner at the expense of the ectexine. The alveolae disappear, and the ectexine becomes thin and homogeneous in the apertural region. Pollen grains of A. manis show many similarities to pollen of modern cycads: a distinct sulcus, a foveolate-fossulate surface pattern, and an infratectum consisting of elongated alveolae. They differ in the ultrastructure of the apertural region, since pollen grains of modern cycads retain the infratectal layer even in the apertural region. A. manis shows differences with earlier studied species of Androstrobus, that point to the heterogeneity of this cycadalean genus.

Pollen morphology and ultrastructure of several Gnetum species: an electron microscopic study

Pollen grains of five Gnetum species have been studied in scanning and transmission electron microscopy: G. africanum, G. funiculare, G. indicum, G. leptostachyum, and G. macrostachyum. The exine ultrastructure was described for the first time for G. funiculare, G. leptostachyum, and G. macrostachyum. The pollen grains are small, inaperturate, and microechinate. The sporoderm includes a rather thin tectum, granular infratectum, and lamellate endexine. The foot layer is indistinct or absent in G. africanum, G. funiculare, and G. macrostachyum and thin in G. indicum and G. leptostachyum. Gnetum africanum differs from other studied species of the genus in having smaller supratectal microechini. They occur on considerably raised exine regions (islands) that are interpreted as an equivalent to the plicae in Ephedra and Welwitschia. In Asian species of Gnetum, a microechinus and area around it are interpreted as equivalent to the islands of G. africanum and the plicae in Ephedra and Welwitschia. The infratectum in G. africanum consists of few, widely spaced large granules in contrast to small densely packed granules of other studied Gnetum species. A comparison of the published and original data on extant pollen of Gnetales and fossil ephedroid pollen shows a great similarity in the sporoderm ultrastructure. Absence of Gnetum-like pollen in the fossil record may be due to their thin ectexine, possible separation of the ect- and endexine or misinterpretation.

A diverse pollen assemblage found on Friisicarpus infructescences (Platanaceae) from the Cenomanian–Turonian of Kazakhstan

Pollen grains found on, or within, pistillate reproductive structures are described for numerous gymnosperms and angiosperms. Attribution of these pollen grains to the macrofossils is often risky and requires additional evidence. This study, based on the material from the Cenomanian–Turonian of Kazakhstan, is the first to document in detail different types of pollen adhering to platanoid infructescences of Friisicarpus sarbaensis. Infructescence parts were examined under SEM in search of pollen. Pollen grains were removed from SEM stubs and studied with LM and TEM. About 250 pollen grains adhering to infructescence axes and carpels were studied; they are small, reticulate (rarely foveolate), tricolpate or tricolporate, and columellate. At least nine pollen types have been distinguished based mainly on the details of the exine sculpturing. The exine ultrastructure was characterized for four prevailing types. Considering pollen morphology and ultrastructure, three types were shown to be produced by platanoids and one was probably ranunculid. Other pollen types are harder to refer to a certain group, though one of them probably belongs to Hamamelidaceae and another one shows exine sculpturing similar to Chloranthaceae pollen. One of the types prevails (about 170 pollen grains) and resembles pollen found on inflorescences of other Friisicarpus species, so we consider that this type was produced by the parent plant. Pollen grains of another type are identical to pollen of Sarbaya radiata from the same locality. The diversity and abundance of different pollen types of the similar size and sculpture found on the infructescences of Friisicarpus sarbaensis favour entomophily of this plant but challenge specific plant-insect specialization.

Palynological study of heterostylous species of Melochia L. (Byttinerioideae-Malvaceae) occurring in Bahia, Brazil

Melochia L. species are morphologically characterized by a pentacarpelar gynoecium with free papillose styles at the apex, whereas some are connate. The genus comprises about 60 species, with 22 occurring in Brazil. We analyzed pollen grains from 12 heterostylous species occurring in the State of Bahia to contribute to the palynology of the Melochia Group, including Melochia betonicifolia A. St.-Hil., M. caracasana Jacq., M. chamaedrys A. St.-Hil., M. hirsuta Cav., M. illicoides K. Schum., M. parvifolia Kunth, M. pilosa (Mill.) Fawc. & Rendle, M. pyramidata L., M. spicata (L.) Fryxell, M. splendens A. St.-Hil. & Naudin, M. tomentosa L., and M. villosa Fawc. & Rendle. Pollen grains were provided from specimens deposited at the CEPEC, HUEFS, and SP herbaria. The floral morphs of all specimens had been previously studied with a stereomicroscope. Acetolyzed pollen grains were investigated by light microscopy, and non-acetolyzed pollen grains were observed by scanning and transmission electron microscopy. It was confirmed in two pollen types of the two floral morphs: (1) the longistylous morph was characterized as medium sized; prolate spheroidal; 3-colporate, with ectoapertures comparatively larger, endoaperture lalongate; reticulate-perforate; exine ultrastructure with nexine differentiated into endexine and a foot layer (M. pyramidata) or undifferentiated (M. betonicifolia); a 4-stratified sexine may also occur; (2) the brevistylous morph showed medium to large-sized pollen grains; oblate spheroidal; 3(4)-colporate, ectoaperture short, endoaperture lalongate; microechinate and echinate; semitectum perforate and microreticulate-rugulate (M. betonicifolia); M. pyramidata wall ultrastructure with nexine showing “internal foramina.” Pollen dimorphism was confirmed in the genus due to heterostyly. The type and number of apertures were not as useful as exine ornamentation to characterize and distinguish the pollen grains.

A contribution to the knowledge of exine ultrastructure in subtribeAnisopappinae(Athroismeae, Asteraceae)

Abstract Pereira Coutinho A., Ortiz S., Valente M., Franca R. & Soares M.: A contribution to the knowledge of exine ultrastructure in subtribe Anisopappinae (Athroismeae, Asteraceae). — Willdenowia 44: 431–437. 2014. — Version of record first published online on 14 November 2014 ahead of inclusion in December 2014 issue; ISSN 1868-6397; © 2014 BGBM Berlin-Dahlem. DOI: http://dx.doi.org/10.3372/wi.44.44314 To better understand the taxonomy and phylogeny of the Anisopappinae and Athroismeae, the exine ultrastructure of two species of the two genera of that subtribe — Anisopappus chinensis Hook. & Arn. and Cardosoa athanasioides (Paiva & S. Ortiz) S. Ortiz & Paiva (both representing the types of the generic names) — were studied with transmission electron microscopy and scanning electron microscopy. As for other Asteroideae and Asteraceae, the existence of a mesoaperture intersecting the foot layer and the upper part of the endexine was established. The exines of both taxa have a Helianthoid pattern of struc...

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.