It has been suggested that pollen ornamentation can be used to distinguish infrageneric groups in Quercus . Here, we document pollen morphology of nearly all species of Quercus Group Ilex and show ...that they share distinctive microrugulate pollen ornamentation. Furthermore, pollen ultrastructure of all six infrageneric groups of Quercus was studied comparatively and evaluated using a phylogenetic framework for Fagaceae. Characteristics of the foot layer, such as its thickness and continuity, and the ratio foot layer to tectum are not stable within infrageneric groups of Quercus . The foot layer in derived groups (Groups Cerris, Quercus, Lobatae) is irregular, discontinuous and thin (type 2 foot layer). Members of Groups Cyclobalanopsis and Ilex either have a regular, continuous, and comparatively thick foot layer (type 1), or a type 2 foot layer. Only Group Protobalanus consistently has a type 1 foot layer and is similar to Trigonobalanus and Colombobalanus among trigonobalanoids, and to castanoids. Because (I) all except for one species of Castanea and Nothofagus have a type 1 foot layer and (II) basal groups in Quercus may have a type 1 foot layer, we suggest that this is the ancestral state in Fagaceae, and that the type 2 foot layer of Fagus is derived.
Dispersed pollen grains of Lagenella martini from the Upper Triassic of Austria were studied by means of light, scanning and transmission electron microscopy. Pollen grains are medium-sized, ...monosulcate, finely striate with differently directed striations on distal and proximal surfaces. The aperture is usually broadly open with rounded ends. The ectexine is composed of a thick tectum, granular infratectum, and thin foot layer. The endexine shows fine lamellation in its outer part. Reported association of Lagenella martini with Stachyotaxus reproductive structures needs a more detailed investigation of the morphology and ultrastructure of the found pollen to make reliable conclusions. A comparison with known fossil and modern non-saccate striate pollen has shown that the studied pollen grains share a number of characters with some gymnosperms and angiosperms with most similarity to Vittatina-like pollen.
•Pollen of Lagenella martini was studied by electron microscopy for the first time.•The exine is characterized by a granular infratectum and lamellate endexine.•The studied pollen grains show most similarity to Vitattina-like pollen.
Abstract
Quercus (oaks) is a large and important genus of woody angiosperms occurring in a wide range of environments and often occupying a dominant position in temperate forests of the Northern ...Hemisphere or being a minor component in some subtropical and tropical forests. A reliable determination of fossil dispersed oak pollen requires combined light, scanning electron (SEM) and transmission electron microscopy (TEM) studies and relevant comparative data on extant oak species. We provide SEM and TEM data on 22 extant Quercus spp., representing all sections of the genus. The main objectives of our study were to clarify the nature of the so-called geniculus, a characteristic equatorial bulge in the exine of the colpus found in many oak species, and to test previous hypotheses about the structural basic units of the exine in Quercus. Our ontogenetic study and oxidative experiment involving several Quercus spp. and one Trigonobalanus sp. resulted in a more accurate interpretation of the nature of the geniculus and exine elements, their different developmental states and, therefore, their more reliable application in the systematics and evolution of the genus Quercus and Fagaceae in general.
Holocene dispersed pollen from two cores from the shelf zone of the Korean Bay and from the deep water zone of the south of the Sea of Japan were studied by means of light and electron (scanning and ...transmission) microscopy. Three sculpture types were observed: rod-like, rugulate-granulate and (micro)verrucate. Ten conventional groups were separated according to the sporoderm morphology and ultrastructure. Possible specific attribution was suggested based on the comparison with published data on modern and fossil oak pollen. The perspective of further application of electron microscopy for this taxon is discussed.
A first occurrence of the genus
Meliosma
(Sabiaceae) is reported from the upper Eocene of the Maoming Basin of South China. This fossil is one of the oldest reliable records of the genus within its ...modern center of diversity. Fossil leaves are assigned to a new species,
Meliosma eosinica
sp. nov. based on leaf morphology and epidermal characters. The leaf epidermal anatomy of fossil
Meliosma
is illustrated for the first time. We also provide the first SEM observation of pollen grains associated with
Meliosma
. This study also documents an occurrence of mites within the leaf domatia previously unknown from the fossil record. We presume that the studied mite belongs to the superfamily Eupodoidea (Arthropoda), and probably the family Eupodidae, which comprises very small soft-bodied cosmopolitan mites occupying a wide range of terrestrial habitats. Additionally, we analyze the damage types on the fossil leaves of
Meliosma
. They exhibit exclusively external foliage feeding damage caused by arthropods and traces of probable fungal infection. A review of currently known fossil occurrences of leaves, fruits, and wood of
Meliosma
provides evidence for the geological and geographical distribution of the genus.
Anatomical characters of Cenozoic pine seed cones are known mainly from North American fossils, while data on cone anatomy of Cenozoic species from Asia remain scarce. To date, only one seed cone of
...Pinus
from the Miocene of eastern China has been studied using micro-computed tomography (micro-CT). A new fossil-species,
Pinus prehwangshanensis
sp. nov., of mummified seed cones from the upper Pleistocene of South China is described using a combination of scanning electron microscopy (SEM) and micro-CT. The new fossil-species combines a mosaic of seed cone morphological and anatomical characters observed in the group of closely related East Asian extant species of subgenus
Pinus
, section
Pinus
, subsection
Pinus
, comprising
Pinus taiwanensis, Pinus hwangshanensis, Pinus luchuensis, Pinus thunbergii
, and
Pinus densiflora
. The data obtained indicate that the characteristic anatomical features of this group were formed no later than the end of the Pleistocene. Based on the external seed cone morphology, the East Asian pine fossils confirm the existence of floristic exchange between continental Asia and the Japan archipelago prior to the formation of the Sea of Japan and later, in the middle Miocene to the late Pliocene, when the connection between the Japanese islands and Eurasian continent became re-established. Pollen grains associated with the new fossil-species are similar to those of some extant pine species related to
P. thunbergii
. A taxonomic and ecological analysis of the Pleistocene plant taxa from the Maoming Basin suggests that the regional climate was a humid subtropical monsoon with hot wet summers and cool dry winters, similar to the present-day climate of northeastern Vietnam.
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.
•Pollen of Pretricolpipollenites bharadwajii were studied by electron microscopy for the first time.•The exine is characterized by a granular infratectum and lamellate endexine.•The studied pollen grains show most similarity to Eucommiidites pollen.
A considerable disparity of pollen characters in the modern Gnetales (including the inaperturate and monosulcate germination types, the psilate, polyplicate and spinulose sculptural types) stands in ...sharp contrast with their ultrastructural uniformity. In all of the ultrustructurally studied living species of
Ephedra,
Welwitschia and
Gnetum, the infratectum is granular, mostly consisting of small granules, while the endexine is uniformly thick and lamellate. The recently discovered fossil gnetophytes are a diverse group, recognized primarily on the basis of their ovulate cupules, but heterogeneous in respect to their pollen organs and pollen morphology. The pollen grains are mostly asaccate or, rarely, bisaccate (
Preflosella,
Dinophyton), with small ruguloid sacci (
Baisianthus) or vestigial protosaccate structures (
Cryptosacciferites). The germination types are inaperturate, cryptoporate, monosulcate and trisulcate. In the majority of forms the infratectum is granular, consisting of small granules, large granules, combinations of various granules, or even columella-like elements; rarely, the infratectum is alveolar. The endexine varies from distinctly lamellate to homogeneous. Our analysis of pollen grain morphology and ultrastructure of extant gnetophytes lends support to phylogenetic relatedness of extinct forms. Palaeobotanical data show a striking parallelism of morphological variations between gnetophytes and angiosperms.
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.
•We describe first evidence of different pollen types adhering to a platanoid infructescence.•Nine pollen types have been distinguished and compared with known angiosperm pollen.•Three types were shown to be produced by different platanoid taxa and one was probably ranunculid.•The possible pollination mode of the plant is discussed in respect to the found diversity of pollen.
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