Aperture variation in the pollen of Nelumbo (Nelumbonaceae)

The evolutionary and developmental origin of tricolpate pollen is of great interest because pollen of this kind defines a major clade of angiosperms (eudicots), a clade that is also well supported by molecular data. We examined evidence that tricolpate and monosulcate pollen types are produced alongside each other in the anthers of Nelumbo flowers, as has previously been reported. Observations of pollen in situ within individual anthers revealed mainly tricolpate pollen produced in tetrahedral tetrads, but also a small percentage of clearly aberrant pollen grains that have a great variety of aperture configurations. Previously published evidence for tetragonal tetrads is not supported, and previously reported monosulcate grains are part of a continuum of variation among the aberrant grains in aperture number, position and form. Other eudicots show similar variability in their pollen apertures. The variation in the pollen of Nelumbo is not exceptional, and may not be more significant than variation seen in the other taxa with regard to the origin of the tricolpate and tricolpate‐derived pollen characteristic of eudicots. Nevertheless further studies of aberrant pollen in Nelumbo and other eudicots, together with comparisons of pollen development in “normal” eudicots and closely related species that show radical, and developmentally fixed, reorganization of apertures and pollen polarity, may be helpful in understanding the processes that controlled the transition from the monosulcate to the tricolpate condition.     

The Discovery of a New Monosulcate Pollen-Zhonghuapollis gen. Nov.and Its Stratigraphical (Significance)

A new Monosulcate pollen has been discovered from the upper partof Lower Cretaceous deposits of Hubei, Jiangsu, Jingxi and Hebei Provinces. Thesepollens have a monosulcate on their distal surface with salient features and differ fromCycadopites and Benettites. We call them Zhonghuapollis gen. nov. They are widespread geographically and only restricted to the later Early Cretaceous deposits, so very useful in stratigraphical dividing and correlation of this deposits.     

Early cretaceous fossil evidence for angiosperm evolution

Morphological, stratigraphic, and sedimentological analyses of Early Cretaceous pollen and leaf sequences, especially from the Potomac Group of the eastern United States, support the concept of a Cretaceous adaptive radiation of the angiosperms and suggest pathways of their initial ecological and systematic diversification. The oldest acceptable records of angiosperms are rare monosulcate pollen grains with columellar exine structure from probable Barremian strata of England, equatorial Africa, and the Potomac Group, and small, simple, pinnately veined leaves with several orders of reticulate venation from the Neocomian of Siberia and the basal Potomac Group. The relatively low diversity and generalized character of these fossils and the subsequent coherent pattern of morphological diversification are consistent with a monophyletic origin of the angiosperms not long before the Barremian. PatuxentArundel floras (Barremian-early Albian?) of the Potomac Group include some pollen and leaves with monocotyledonous features as well as dicotyledonous forms. Patuxent angiosperm pollen is strictly monosulcate and has exine sculpture indicative of insect pollination. Rare Patuxent-Arundel angiosperm leaves are generally small, have disorganized venation, and are largely restricted to sandy stream margin lithofacies; the largest are comparable to and may include ancestors of woody Magnoliidae adapted to understory conditions. Patapsco floras (middle to late Albian?) contain rapidly diversifying tricolpate pollen and several new complexes of locally abundant angiosperm leaves. Ovate-cordate and peltate leaves in clayey pond lithofacies may includeancestors of aquatic Nymphaeales and Nelumbonales. Pinnatifid and later pinnately compound leaves with increasingly regular venation which are abundant just above rapid changes in sedimentation are interpreted as early successional “weed trees” transitional to but more primitive than the modern subclass Rosidae. Apparently related palmately lobed, palinactinodromous leaves which develop rigidly percurrent tertiary venation and become abundant in uppermost Potomac stream margin deposits (latest Albian-early Cenomanian?) are interpreted as riparian trees ancestral to the order Hamamelidales. Comparisons of dated pollen floras of other regions indicate that one major subgroup of angiosperms, tricolpate-producing dicots (i.e., excluding Magnoliidae of Takhtajan) originated in the Aptian of Africa-South America at a time of increasing aridity and migrated poleward into Laurasia and Australasia. However, the earlier (Barremian) monosulcate phase of the angiosperm record is represented equally in Africa-South America and Laurasia before marked climatic differentiation between the two areas. These trends are considered consistent with the hypothesis that the angiosperms originated as small-leafed shrubs of seasonally arid environments, and underwent secondary expansion of leaf area and radiated into consecutively later successional stages and aquatic habitats after entering mesic regions as riparian “weeds,” as opposed to the concept that they arose as trees of mesic forest environments.     

中国马鞭草科植物的花粉形态

本文对我国18属91种3变种马鞭草科(Verbenaceae)植物的花粉形态进行了详细地观察研究。其中对15属27种进行了扫描电镜观察。本科为花粉多类型的科之一。根据萌发孔的数目、特征和纹饰特点,本文将马鞭草科分为9个花粉类型:1.具疣3沟花粉类型;2.具刺3沟花粉类型;3.具细网8沟花粉类型;4.具模糊颗粒-细网3沟花粉类型;5.具网3沟花粉类型;6.具散沟(6-8条)花粉类型;7.具3孔花粉类型;3.具细网3沟花粉类型,4.具模糊颗粒一细网3沟花粉类型,5.具网3沟花粉类型,6.具散沟(6-8条)花粉类型,7.具3孔花粉类型,8.具3孔沟花粉类型,9.具3(4)孔沟花粉类型。     

Pollen Bud Formation and its Role in Ophiorrhiza spp.

The anther in Ophiorrhiza is dithecous and tetralocular, itsdevelopment being of the dicotyledonous type. The anther wallcomprises epidermis, endothecium, middle layer and secretorytapetum. The pollen grains are tricolpate and triporate. Themicrospore nucleus undergoes division to form a vegetative nucleusand a generative nucleus and protrusions (pollen buds) are formedfrom the germ pores after the first division of the microsporenucleus. The vegetative nucleus moves into one of these budsor first breaks into a number of irregularly sized nuclear particleswhich enter into one, two or into all three buds, where theydegenerate. Then the pollen buds are separated and the generativenucleus divides inside the pollen tube to form two sperms. Ophiorrhiza harrisiana, Ophiorrhiza hirsutula, microsporogenesis, pollen buds, vegetative nucleus     

Appomattoxia ancistrophora gen. et sp. nov., a new Early Cretaceous plant with similarities to Circaeaster and extant Magnoliidae

A new genus and species of fossil angiosperm (Appomattoxia ancistrophora) is established based on well-preserved fruiting units and associated pollen from the Early Cretaceous (Early or Middle Albian) Puddledock locality in the Potomac Group sequence of Virginia, eastern North America. Fruiting units are small, unilocular, and with a single, pendulous, orthotropous seed. The fruit surface is characterized by densely spaced unicellular spines with hooklike tips, which probably functioned in biotic dispersal. Pollen grains adhering to the stigmatic area of many specimens are monocolpate and tectate with granular to columellate infratectal structure, and are similar to dispersed grains assigned to Tucanopollis and Transitoripollis. Comparison of fossil Appomattoxia ancistrophora with extant plants reveals an unusual combination of characters that includes similarities with some magnoliid taxa, particularly Piperales (Piperaceae, Saururaceae) and Laurales (Chloranthaceae), as well as the monotypic ranunculid family Circaeasteraceae. Appomattoxia ancistrophora differs from extant Piperales in having a pendulous rather than erect ovule, and differs from extant Circaeaster in details of the fruit wall, as well as the presence of monosulcate rather than tricolpate pollen.     

Studies on Pollen Morphology of Pulsatilla Mill.

Pollen grains of 18 species of Pulsatilla in Ranunculaceae distributed in Asia and Europe were examined by LM and SEM, and exine ultrastructure of tricolpate pollen grains of P. chinensis and of pantoporate pollen grains of P. campanella was examined by TEM. Pulsatilla pollen is divided into four major types based on the aperture character, i.e. tricolpate, di- and tricolpate, pantocolpate and pantoporate. The revolutionary trend of pollen types is as follows: tricolpate→pantocolpate→pantoporate. Surface spinulate and perforate. According to density and size of sptnulae and distribution of perforation, the pollen grains of the genus can be divided into two groups. Thin sections of P. chinensis and P. campanella show endexine thickened at colpi and ora. Ektexine consists of a foot layer, a collumellae layer and a continuous, perforate tectum. The columallae layer is thicker than foot layer and tectum. Pollen morphology of Pulsatilla is similar to that of Anemone, but different in the distribution of spinules and perforation. Pollen information supports Wang’s view about systematic arrangment of species of Pulsatilla in China.     

On Mulleripollis gen. nov., a pollen tetrad from the upper cretaceous of the Bengal Basin,West Bengal,India

A tetrahedral tetrad of tricolpate, striate pollen from the Upper Cretaceous subcrop sediments of the Bengal Basin has been described under a new generic name, Mulleripollis gen. nov., with the type species Mulleripollis bolpurensis gen. et sp. nov. It has been noticed that this pollen tetrad is restricted to the Upper Cretaceous Bengal Palynological Zone, which is stratigraphically significant. The natural affinity of the pollen could not be established.     

Palaeopalynological Evidence of Phylogeny in Hamamelidaceae

This paper deals with evolution, classification and pollen morphology of the Hamamelidaceae, an important family in phylogeny of angiosperms. I. Pollen morphology and systematics of modern Hamamelidaceae. The pollen morphology of the family may be divided into the following four types: (1) Tricolpate: Hamamelis, Loropetalum, Mytilaria, Corylopsis, Sysopsis, and Distylum etc.; (2) Tricolpate with operculum: Disanthus; (3) Tricolporate: Rhodoleia; (4) Pantoporate: Liquidambar. The tricolpate pollen of the Hamamelidaceae is a primitive type in angiosperms, but the most ancient type is monocolpate pollen. Therefore, the family might have evolved from the Magnoliaceae of the monocolpate pollen. The pantoporate pollen is an evolutionary type in the family. It might have evolved from the tricolpate pollen. II.The fossil pollen of the Hamamelidaceae 1 .General introduction of the fossil pollen of the family Hamamelidaceae The most’ancient fossil pollen belonging to the family was found in the middle-late Early Cretaceous. Palynologists call the fossil pollen of the Hamamelidaceae Retitricolpites, which consists of three genera: Hamamelis L.,Corylopsis Sieb. et Zucc and Fothergilla Murr. Liquidambar is of an advanced type in the fossil pollen of the Hamamelidaceae. It was found in the period from the Palaeogene to the Neogene in China. 2. The geological history of the Hamamelidaceae may be divided into the following four stages: (A) The Early Cretaceous stage or origination stage. The family may be evolved from Magnoliales in the middle-late Early Cretaceous. (B)the Late Cretaceous stage or formation stage. The family is much developed in the period. (C) The Tertiary stage or development stage. The family was a much developed one among angiosperms. (D)The Neogene to modern stage or perfection stage. The evolutionary type, the Liquidambar type of the Hamamelidaceae, was much developed in the Neogene. III. The palaeopalynological evidence of evolution of the Hamamelidaceae The earliest fossil pollen of angiosperms was found in the Barremian (Early Cretaceous) in England, Israel, the United States of America etc., and was named as Clavatipollenites by Couper (1953). In recent years, Clavatipollenites was also found in the middle-late Early Cretaceous in Nei Monggol and Jiangxi Province of China. We also found Retitricolpites in the middle-late Early Cretaceous in Nei Monggol and Jiangxi Province. Retitricolpites, belonging to the Hamamelidaceae, is a primitive type among angiosperms, but it is younger than Clavatipollenites. Therefore, the pollen of Hamamelidaceae may have evoloved fromClavatipollenites, which may have evoloved in turn from that of Magnoliales.     

Pollen morphology inParis and its related genera

Pollen grains ofParis, Medeola, andScoliopus have been examined with light, scanning electron, and transmission electron microscopies.P. quadrifolia L.,P. verticillata Bieb.,P. delavayi Franch. andP. polyphylla Smith have monosulcate pollen characterized by psilate, foveolate or reticulate exine sculpture. In contrast to the former species,P. japonica (Fr. et Sav.) Franch. andP. tetraphylla A. Gray have monosulcate pollen with gemmate (rarely rugulate) exine.Medeola has monosulcate pollen with reticulate exine that is distinct from that ofParis. Scoliopus has monosulcate pollen characterized by a peculiar reticulate exine pattern. The palynological evidence suggests thatParis andTrillium are closely related to each other, andMedeola andScoliopus should be separated fromParis andTrillium.     

Pollen diversity in Aquifoliales

Aquifoliales, as currently circumscribed, comprise five families and 20 genera, most of which have not been compared with regard to their pollen. Generic relationships within the order have not been fully resolved with molecular data, but pollen can provide a potential source of characters for future phylogenetic studies. To assess diversity in the order, pollen from 19 genera was examined with light and scanning electron microscopy. Pollen is typically tricolpate to triporate, although grains with one to nine pores were observed. Grains are small to medium, with a polar axis of 6–44 μm and an equatorial axis of 10–47 μm. Irregular pollen was recorded from nine genera. Exine patterning is diverse at the generic level and includes psilate, microechinate, striate to reticulate and clavate types, and is quite complex in some genera. All but four genera of Aquifoliales can be readily distinguished by their pollen, if heavy deposits of pollenkitt (present in 11 genera) are removed during and after acetolysis. Pollen from multiple taxa of Gomphandra, the second most diverse genus in the order, was surveyed to investigate species boundaries. Specimens of Gomphandra from continental Asia exhibited seven different pollen morphologies, suggesting that exine patterns may be useful for the recognition of species in that region. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 169–190.     

Pollen morphology ofLactoridaceae

The pollen wall ultrastructure of the primitive AngiospermLactoris fernandeziana Phil. (Lactoridaceae) is described. The monosulcate aperture, granular wall structure and sacci (all primitive features) suggest placement of this family in theMagnoliales. Pollen ofLactoris is compared to fossil dispersed pollen from the Lower and lower-Upper Cretaceous. The fossil pollen shares characteristics which are restricted to theLactoridaceae suggesting that this family was present during the early Cretaceous.     

POLLEN WALL ULTRASTRUCTURE OF SELECTED DISPERSED MONOSULCATE POLLEN FROM THE CENOMANIAN,DAKOTA FORMATION,OF CENTRAL USA

Seven dispersed monosulcate pollen taxa from the Dakota Formation of Minnesota, Nebraska, and Kansas were examined ultrastructurally. Rugubivesiculites rugosus has gymnosperm affinities based on its anasulcate aperture and the presence and nature of the formation of sacci. Stellatopollis sp. has exine sculpturing restricted to taxa with angiosperm affinities and is monosulcate. The affinities of the other five monosulcate taxa are uncertain and the exines are tectategranular. The sulcus in many of the remaining five taxa are flanked by small flange-like sacci. These five taxa have features found in gymnosperms and also some features of primitive extant angiosperms. The combination of characters of the pollen types presented here does not entirely agree with our current concept of primitive pollen characters as understood from extant ranalean angiosperms.     

Early history of theJuglandaceae

The major radiation of theJuglandaceae occurred during the early Tertiary as recorded by the proliferation of juglandaceous pollen and the appearance of fruits representing extinct and extant genera of the family. Juglandaceous pollen types of the Paleocene were predominantly triporate and exhibited a greater diversity in patterns of exinous thinning than occurs in the family today. Analyses of in situ pollen from early Tertiary juglandaceous inflorescences confirms the taxonomic value of certain patterns of exinous thinning. Data from co-occurring fruits and pollen indicate that relatively unspecialized, isopolar triporate pollen of the type presently confined to the tribeEngelhardieae also occurred in other tribes of the family during the Paleocene. Pollination has been mostly anemophilous throughout the Tertiary. Both wind and animal fruit-dispersal syndromes were established early in the radiation of the family but a greater diversity of wind-dispersed genera has prevailed.     

Studies on the Pollen Morphology of the Chinese Palmae

This paper deals with morphology of the recent pollen grains of 26 species representing 16 genera and some fossil pollen of the Chinese Palmae. They are examined with the light microscope and scanning electron microscope. On the basis of the types of aperture and the distribution of fossil pollen and lithophyll in the strata, the trends of the evolution of the family Palmae are discussed. This paper points out that the monosulcate pollen belongs to the most predominent and more primitive aperture type in this family and that there is a trend in which the trichotomosulcate, annulocolpate, disulcate etc. are derived from the monosulcate pollen.     

Pollen aperture morphology in Arecaceae: Application within phylogenetic analyses,and a summary of record of palm-like pollen the fossil

For a monocotyledonous family, the Arecaceae possess unusually varied pollen, not only in aperture number and orientation, but also in exine ornamentation. Although the majority of species have monosulcate pollen, 17 aperture types, and 13 exine types, have been described. The family belongs to a minority of monocotyledonous families in which both successive and simultaneous cytokinesis occur. The aperture types that have been described for the Arecaceae can be separated into those associated with successive, and those associated with simultaneous, cytokinesis. Palms have a long fossil record, mainly leaves and pollen, but also fruits, stems, and roots. Flowers have also been recovered. Distinctive aperture and/or exine combinations, in the pollen of some species, have prompted comparisons with fossil pollen taxa, certainly from the Late Cretaceous onwards. Occurrences of various fossil pollen taxa, frequently associated with palms, are reviewed, and their morphologies, particularly aperture characteristics, are compared with those of living palm pollen. The systematic rarity of most palm aperture types places limitations on their value in cladistic analyses. Nevertheless, certain aperture characters are of value, and do contribute to a better understanding of the evolution and phylogeny of the family. The differences between aperture types and aperture characters are addressed. The seventeen aperture types are described, and the interpretation and use of aperture characters in cladistic analyses of the Arecaceae are discussed.     

Studies on Pollen Morphology in Tiliaceae of China

Pollen morphology of 44 species representing 9 genera of Tiliaceae in China was examined under light microscope, 10 of them were observed with scanning electron microscope. Nine genera involved in this paper are: Colona. Corchoropsis, Corchorus, Excentrodendron, Grewia, Hainannia, Microcos, Tilia and Triumfetta The pollen grains of Tiliaceae are eurypalynous. Based on the aperture type and ornamentation, they may be grouped into four types: (1) The Grewia type, pollen grains tricolporate: Colona, Corchorus, Grewia, Microcos and Triumfetta, (2) The Tilia type, pollen grains brevitricolporate: Hainania and Tilia, (3) The Corchoropsis type, pollen grains triporate, spinate: Corchoropsis, and (4) The Excentrodendron type, pollen grains triporate, reticulate: Exce ntrodendron. The significance of pollen morphology in taxonomy of Tiliaceae is discussed. The palynological data seem to support the separation of Microcos from Grewia and the transfer of Corchoropsis to Sterculiaceae from Tiliaceae.     

蜘蛛抱蛋亚族的花粉形态

本文研究并报道了百合科蜘蛛抱蛋亚族的花粉形态,主要结论如下：1．开口箭属含两种花粉类型即：(1)单槽、椭圆形;(2)无萌发孔、球形。具单槽、椭圆形花粉的种类含单型性核型,花形较小,柱头小而花柱短,雄蕊高于柱头;无萌发孔、球形花粉的种类则为单型性核型,花形较大,柱头常高度膨大,雄蕊常着生在花被筒基部。2．万年青属花粉为椭圆形,具单槽;蜘蛛抱蛋属花粉则为球形,无萌发孔;开口箭属花粉一部分与万年青属相似,另一部分则与蜘蛛抱蛋属雷同。3．蜘蛛抱蛋亚族中最原始的花粉类型为单槽椭圆形,具孔状或网状外壁纹饰。球形,无萌发孔,外壁具皱波状、瘤状或芽孢状纹饰的花粉为派生类型。4．蜘蛛抱蛋亚族种下花粉形状、萌发孔类型和外壁纹饰基本稳定,可作为分种特征。     

Significance of monosulcate pollen abundance in Mesozoic sediments

Monosulcate pollen was produced by at least six plant orders in the Mesozoic. Megafossils of these orders are abundant in many Mesozoic sediments, but dispersed monosulcate pollen grains are commonly less than 10% of total sporomorphs (spores and pollen) in a sample. This paper presents possible explanations for the different relative frequencies of megafossils and pollen grains of monosulcate-producing plants (some of the explanations apply to only a few taxa): fragility of the pollen exines, destruction of the pollen on the plant by insects, poor pollen dispersal because of zoophily and small plant size, and, probably most importantly, overrepresentation of the plants by their generally deciduous leaves. Mesozoic monosulcate pollen was different in several ways from pollen of modern gymnosperms; furthermore, monosulcate-producing plants were not as abundant in the Mesozoic vegetation as has been generally thought.     

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.