The classification and evolution of pollen types ofPlanchonioideae (Lecythidaceae)

The pollen type ofPlanchonioideae is unique among the angiosperms in its syntricolpatism associated with the marginal ridge, marginal groove, and polar cushion; it has been studied byJ. Muller, who classified it into three types, mainly with a light microscope. In the present study, pollen grains of the six constitutent genera were studied with a scanning electron microscope, five additional pollen types were recognized. Of the eight pollen types the one with sealed polar ectoapertures and weakly developed marginal ridges, without marginal grooves and polar cushions is regarded as the most primitive. Evolutionary trends proceeded with the opening of the polar ectoapertures, the complication of the polar cushions and marginal grooves. In the most advanced form, the marginal ridges and marginal grooves coalesced to form two concentric rings, whereas the polar cushions were secondarily reduced.     

Infrageneric variability of pollen morphology in Palaua (Malveae,Malvaceae) and the taxonomic utility of quantitative pollen characters

Palaua (Malvaceae) comprises 15 species endemic to the coastal deserts of Chile and Peru. Previous molecular phylogenetic analyses have shown that this genus is monophyletic and can be subdivided into three clades. In the present study, pollen morphology of all species of Palaua was examined using light and scanning electron microscopy to determine whether it provides additional data in support of the proposed infrageneric groups. The pollen grains are spheroidal, medium to large in diameter, spinose and pantocolporate – the ectocolpi are very short. The tectum is perforate and characterised by granula. In all species the nexine is of a similar thickness in all areas of the pollen grain, while the sexine thickness varies, being notably thicker in the areas where the broad spine bases are sited (‘spine cushions’). Many of the quantitative characters have conspicuous variability, but the variability shows considerable overlap between species. Nonetheless, P. guentheri, P. inconspicua, P. malvifolia and P. modesta are united as a group by having the smallest pollen grains with the smallest apertures, the shortest spines and the shortest interspinal distance. This grouping reflects only partially the suggested infrageneric clades, although it does tend to unite the species with the smallest flowers. A possible link between reproductive resources and pollen size is also considered, as well as the influence of polyploidy. However, the taxonomic utility of these quantitative characters is weakened by species with more than one cytotype.     

A new lycopod, Novgorodendron conophorum gen. et sp. nov., from the Lower Carboniferous of the Moscow Syneclise

A new lycopod, Novgorodendron conophorum gen. et sp. nov., is described from the Upper Visean deposits of the Kamenka River, near the town of Borovichi (Novgorod Region). The morphology of the leaf cushions of the new plant implies its intermediate position between the families Sublepidodendraceae Chaloner et Boureau and Lepidodendraceae Endlicher. The bases of the leaf cushions have peculiar conical appendages, a previously unknown morphological feature not recorded from other lycopods. We propose the term basal conical appendages for them. The interpretation of some epidermal elements in the leaf cushions of the Lepidodendraceae is revised. The structures of the leaf cushions that were previously treated as either stomata or cells with cystoliths are shown to be sunken multicellular trichomes.     

Notes on the floral morphology in Vivianiaceae (Geraniales)

The functional floral morphology of the three genera of Vivianiaceae (= Ledocarpaceae, Geraniales), Rhynchotheca, Viviania and Balbisia, is compared. Likely pollination mechanisms are inferred from morphology and field observations. The flowers of Viviania are nectariferous and apparently zoophilous with nectar as the (primary) pollinator reward. Balbisia has pollen flowers without nectaries, its showy corolla indicates that it is also zoophilous with pollen as sole pollinator reward; bees were observed as flower visitors. One taxon (B. gracilis) may be anemophilous. Rhynchotheca has flowers without petals, with large, pendulous anthers and lacks nectaries. It shows synchronous mass flowering in its natural populations and is evidently anemophilous. A comparison with other Geraniales shows that nectar flowers with small anthers are likely the ancestral condition in Vivianiaceae. This suggests that the pollen flowers with larger anthers of Balbisia and Rhynchotheca may represent an apomorphic condition. The documentation of pollen flowers and anemophily in Vivianiaceae expands the range of known floral and pollination syndromes in Geraniales.     

Pollen morphology of the Thymelaeaceae in relation to its taxonomy

 Pollen morphology of the four subfamilies of Thymelaeaceae sensu Domke (1934) was examined using LM, SEM and TEM. The variation of the exine architecture allows to distinguish four pollen types and three subtypes. Distribution of pollen types proves to be widely correlated with the occurrence of characters from wood anatomy and flower morphology. If pollen types are connected with subfamilies sensu Domke (1934), Gonystyloideae, Thymelaeoideae and Synandrodaphnoideae are stenopalynous, whereas Aquilarioideae are eurypalynous. Based on pollen morphology as well as on other characters it is evident that Aquilarioideae are not monophyletic. Its genera Aquilaria and Gyrinops are more closely related to Thymelaeoideae and Synandrodaphnoideae than to other genera of Aquilarioideae sensu Domke (1934). The remaining genera of Aquilarioideae Deltaria, Solmsia and Lethedon are most similar to Gonystyloideae and therefore are included in this subfamily, as it was suggested by Airy Shaw (1979). Furthermore, palynological and other characters favour the transfer of Octolepis from Aquilarioideae to Gonystyloideae. The re-circumscribed Aquilarioideae together with Thymelaeoideae and Synandrodaphnoideae are shown to form a monophyletic group. Received August 8, 2001 Accepted December 7, 2001     

POLLEN MORPHOLOGY AND ULTRASTRUCTURE OF KRAMERIA (KRAMERIACEAE): UTILITY IN QUESTIONS OF INTRAFAMILIAL AND INTERFAMILIAL CLASSIFICATION

The genus Krameria is currently recognized as an enigmatic, monotypic family of dicotyledons. Previous studies of morphology, anatomy, and cytology have been unable to establish unequivocably its phyletic affinities. We report here the results of an intensive investigation of the pollen of Krameria using light, scanning electron (SEM), and transmission electron microscopy (TEM). Pollen characteristics of the genus were compared to those of all families referred to the Polygalales and to selected species of the Leguminosae-Caesalpinoideae, both groups with which Krameria has historically been allied. Superficially, the pollen of Krameria resembles that of the legumes more than that of genera in the Polygalales. However, in ultrastructure, it differs from the pollen of all taxa investigated from both groups. Within Krameria, several variations of a basic type of 3-colporate pollen are discernible. Species with similar pollen variants appear, on the basis of other morphological data, to represent natural groups within the genus. Nevertheless, an arrangement of groups of species of Krameria from “least” to “most” specialized, based on a logical sequence of modification of the pollen morphology, does not agree with any sequence of specialization using other morphological or ecological characters. It is concluded that pollen morphology and ultrastructure has systematic value for intrafamilial groupings of the Krameriaceae but that palynological modifications are incongruous with trends of specializations of other characters and, like many other lines of investigation, pollen studies do not provide significant data as to the phylogenetic affinities of the family.     

Pollen morphology within the Monodora clade,a diverse group of five African Annonaceae genera

Pollen morphology has played a major role in elucidating infrafamiliar‐level systematics and evolution within Annonaceae, especially within the African genera. The Monodora clade is composed of five genera, Asteranthe, Hexalobus, Isolona, Monodora and Uvariastrum, which are restricted to Africa and contain together c. 50 species. A molecular phylogeny of the family showed that the monophyly of the Monodora clade is strongly supported and that it is part of a larger clade of 11 African genera. In order to support classification a detailed survey was made of the pollen morphological variation within the Monodora clade, using scanning and transmission electron microsopy. For the two most species‐rich genera, Isolona and Monodora, a molecular species‐level phylogeny was used to assess the taxonomic usefulness of the pollen characters. The survey showed a wide range of pollen morphological diversity. The most conspicuous variation concerned the occurrence of monads without a thicker outer foliation in the basal exine layer in Isolona in contrast to tetrads with a thicker outer foliation in Asteranthe, Hexalobus, Monodora and Uvariastrum. At the infrageneric level, Hexalobus, Isolona and Monodora showed the largest diversity, with various pollen types based on tectum morphology. Hexalobus is exceptional with three types within only five species. The pollen types defined in this study are hardly useful in characterizing major groups identified within both Isolona and Monodora, but they do illustrate relationships within smaller groups.     

Function and evolution of the adhesion-capture apparatus ofStenus species (Coleoptera,Staphylinidae)

 Further to basic investigations, additional histological and scanning electron microscopical studies of the anatomy and morphology of the adhesion-capture apparatus in species of the genus Stenus have been carried out to achieve a better understanding of its mode of working and evolution. An interspecific morphological comparison of the sticky cushions (paraglossae) of the labium of 47 Stenus species has established that, in most of the investigated species, they represent a general type that has apparently been modified in different ways during the course of evolution. These changes primarily concern the number of adhesive setae on a cushion and the degree of branching of a single adhesive seta. It has been shown experimentally that larger sticky cushions and higher numbers of adhesive setae or adhesive contacts improve adhesion and thus lead to enhanced capture success. In addition to the morphological comparison of the paraglossae, some general aspects of the functional anatomy and morphology of the labium have been examined. It has been established that, during attack, the sticky cushions and the tips of the sense-spines are directed frontally with respect to the prey. This concurrent erection of both paraglossae and the glossae is conditioned by an exocuticular groin that connects the glossae and paraglossae on the left and on the right. The interior of the sticky cushions is made up of a loose reticulum of endocuticular fibres. This cushion-like endocuticle may absorb the thrust caused by the impact of the sticky cushions on the prey. All tissue and chitinous components within the connecting tube of the labium are surrounded by an extra inner covering that separates the tissue within the labium from the exterior wall of the labium. During the protrusion of the labium, this inner tube is most probably required to direct the haemolymph, flowing into the interior of the labium, towards the front. The hypopha- rynx is situated directly in front of the opening of the mouth and narrows the opening into the pharynx. It may be well suited for retaining large food pieces in front of the mouth in order to prevent their premature movement towards the mouth. Accepted: 12 October 1995     

Modern pollen assemblages from Reasi (Jammu and Kashmir), India: a tool for interpreting fossil pollen records

Twenty five surface samples/moss cushions were collected for palynological analysis from open areas of Reasi District, Jammu and Kashmir (India). These samples were used to investigate the relationships between extant vegetation and modern pollen spectra, which serve as modern analogue for the reliable ecological interpretation of fossil pollen records. The present vegetation in the region comprises tropical dry deciduous forests and subtropical pine forests with scattered stands of oak. The pollen analysis reveals that Pinus sp. (average 69% in the pollen assemblages), amongst the conifers, dominates the pollen rain, which can be attributed to its high pollen productivity and exceptional pollen dispersal efficiency. Cedrus sp. and Podocarpus sp. pollen contribute with an average of 16 and 5% to the total pollen rain. Other conifers such as Picea sp., Abies sp., Juniperus sp. and Tsuga sp., as well as broad-leaved taxa such as Quercus sp., Alnus sp., Betula sp., Carpinus sp., Corylus sp., Juglans sp., Ulmus sp., Salix sp., Elaeocarpus sp., Mallotus sp. and Aesculus sp., have lower averages of 1 to 4.5% in the total pollen rain which could be either due to their poor pollen dispersal efficiency or to the poor preservation in the samples. Tubuliflorae (average 25%), Poaceae (average 6.26%), Cerealia and other crop plants (average 7.68%) are other prominent taxa in the pollen rain. The nearly complete absence of members of tropical dry deciduous forests in the pollen spectra likely is due to the fact that most species in this vegetation type are not wind pollinated.     

CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato-reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.     

FERAXOTHECA GEN. N., A LYGINOPTERID POLLEN ORGAN FROM THE PENNSYLVANIAN OF NORTH AMERICA

The pollen organ Feraxotheca gen. n. is described from Pennsylvanian age coal balls from the Lewis Creek, Kentucky, locality. The fructifications consist of bilaterally symmetrical synangia composed of a basal pad supporting elongate sporangia that are laterally appressed for the entire length of the sporangial cavities. Sporangial tips extend over the center of the synangium and delimit a small open area, while the bases arise from a parenchymatous cushion that is bounded by short tracheid-like cells. Each synangium is borne on the surface of an expanded pinna tip and is surrounded by a small amount of laminar tissue that envelopes the base of the synangium. Ultimate pinnae are rectangular in transverse section, possess an elliptical vascular bundle surrounded by canals containing a yellow froth-like substance, and have a cortex of elongate cells that radiate from the center of the axis. Sporangia contain small (40–64 μm), radial, trilete spores ornamented by regularly spaced coni or blunt tipped grana. Feraxotheca is compared with the compression genus Crossotheca and some new ideas are advanced concerning the morphology of this compression genus. The obvious differences between Feraxotheca and other lyginopterid pollen organs strongly suggests that the Lyginopteridaceae, as it is currently interpreted, is an unnatural family.     

The systematic value of pollen morphology in Smilacaceae

Smilacaceae are a small family of dioecious, mostly climbing, net-veined monocotyledons with a cosmopolitan distribution. Relatively little is known about the variation of pollen morphology within the family. For this reason, and to investigate the systematic value of palynology in Smilacaceae, pollen from 125 species of Smilax, Heterosmilax, and Ripogonum was examined using light and scanning electron microscopy. Ten of these were examined further by transmission electron microscopy. Four distinct pollen types grouped into two major pollen classes were distinguished: Class 1, represented by the pollen of all Smilax and Heterosmilax species, is mostly spheroidal, inaperturate, and spinulate or microspinulate, with a thin, fragile exine of varied sculpturing; three pollen types are represented within this class. Class 2 is found only in Ripogonum and contains a single pollen type with prolate, monosulcate, reticulately-sculptured pollen. The unique pollen morphology of Ripogonum supports its removal from Smilacaceae. In contrast, the characteristics of Heterosmilax pollen intergrade with those seen in Smilax, suggesting that the former might be better reduced to synonymy with the latter. A key to the identification of these pollen types is presented along with a discussion of geographic and possible evolutionary trends among them.     

Pollen morphology in Cytisus (Papilionoideae,Leguminosae) from Morocco and the Iberian Peninsula

Although it is generally accepted that the tribe Genisteae has rather homogeneous pollen, we have found considerable variation in pollen size and morphology in Cytisus and related genera (Argyrocytisus and Chamaecytisus), which match taxonomic groups defined on morphological grounds. The results of Principal Component Analysis of pollen characteristics show the following: Cytisus Sect. Alburnoides is well-delimited, with the smallest pollen grains and the simplest pattern in the tectum, fossulate-perforate to perforate; No separation of C. villosus (Sect. Cytisus) from Sect. Alburnoides is observed; Cytisus Sect. Spartopsis, with the largest pollen grains and reticulate to reticulate-fossulate ornamentation, forms an isolated group; C. fontanesii (Sect. Heterocytisus) stands apart from other Cytisus species by its homogeneous ornamentation and the perforate instead of psilate-punctate margo. Thus, the pollen data supports its transfer to the separated genus Chronanthos; Pollen ornamentation and morphology also support the separation of Argyrocytisus battandieri and Chamaecytisus mollis from Cytisus.     

Studies in Montia L. and Claytonia L. and Allied Genera

The pollen morphology of several genera in Portulacaceae is described. Particular attention has been paid to the genera of the subfamily Montioideae, as a stage of continued monographical studies. Among genera especially dealt with are Claytonia, Montia, Crunocallis, Naiocrene, Neopaxia, Mona, Maxia, Limnalsine, and Montiastrum. In the taxonomical treatment of these genera the pollen morphology has proved to afford many important additional characters.

The pollen grains of Claytonia are distinguished from those of the remainder in being 3-colpate. The grains of the Claytonia-type have many similarities with those of Lewisia, a genus of the subfamily Portulacoideae. The other genera of Montioideae have pantocolpate pollen grains. Among these genera several different pollen types are distinguished, chiefly with regard to the sexine structures and the aperture membranes. The Montiastrum-type is especially interesting, with tholate grains, a particular pollen type not met with in any other genus in the family. The pollen morphology of some genera in the Portulacoideae is also treated. In some species in Calandrina and Talinum pantotreme pollen grains are observed with apertures transitional between pori and colpi. The apertures of the pantotreme grains are arranged in characteristic patterns.

Particular attention has been given to the variation of the pollen morphological characters. This variation has been examined with regard to the differences between different populations of the same species as well as between different species. The greatest variation has been observed in the shape and size of the grains. The structure and sculpture and thickness of the sexine and the aperture membranes are less variable. Some polyploid taxa are connected with the occurrence of pollen grains with divergent and varying aperture numbers.

In a survey of the genera the taxonomical results of the investigation are presented with particular regard to the pollen morphology. The new genus, Maxia Ö. Nilss., is described. One new species, Montia clara Ö. Nilss., is described and some new combinations are made.

Pollen morphological diagnoses are given for 46 different taxa. The aperture conditions for 96 different species are presented.     

Microsporogenesis,microgametogenesis, and pollen morphology of <Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis> L. in China

Ambrosia artemisiifolia L. from Ambrosia of the Heliantheae of the Asteraceae family is a recognized harmful weed worldwide and one of the major invasive foreign plants in China. In this study, we investigated its reproductive features, focusing on its microsporogenesis, microgametogenesis, and pollen morphology. The results show that (1) Ambrosia artemisiifolia L. is a dicotyledonous plant and has spherical, tricolpate pollen grains with spiny outer wall; (2) its anther wall comprises four layers, namely epidermis, endothecium, middle layers, and amoeboid tapetum; (3) cytokinesis of microspore mother cells is successive; (4) most of tetrads are tetrahedral; and (5) mature pollen grains are three-celled. In conclusion, although Ambrosia artemisiifolia L. is a dicotyledonous plant with tricolpate pollen, its microsporogenesis is successive, which is different from typical dicots.     

The corystosperm pollen organ Pteruchus from the Triassic of antarctica

The permineralized corystosperm pollen organ Pteruchus is described from the early Middle Triassic of Antarctica. Pteruchus fremouwensis consists of an axis bearing numerous, helically arranged microsporophylls, each of which terminates in a distal flattened head. The axis is 1–2 mm in diameter and eustelic. Spherical to elliptical secretory cavities are present in the ground tissue of the axis, microsporophyll, and pollen sac wall. The basal stalk of the microsporophyll is vascularized by a C-shaped strand that gives rise to a midvein and numerous lateral veins in the distal head. At least 38 pollen sacs are borne on the abaxial surface of the microsporophyll head. These are arranged in pairs on either side of lateral veins. Each pollen sac is sessile, elongated, and uniloculate. The pollen sac wall is several cell layers thick early in ontogeny, but reduced to a single layer in thickness when mature. Dehiscence is longitudinal along the inner surface. Pollen is monosulcate and bisaccate, and of the Alisporites-type. The Triassic specimens are the first structurally preserved pollen organs of the Pteruchus-type and can be related to the associated corystosperm stem and leaf genera based on the presence of unique secretory cavities. The morphology of Pteruchus and the relationship of this pollen organ with other Mesozoic and Paleozoic pollen organs is discussed.     

Triaperturate pollen in the monocotyledons: configurations and conjectures

Triaperturate pollen are known in at least twenty seven genera of monocotyledons. Differences between aperture type and polarity indicate that the development of three apertures has occurred a number of times. Mode of cytokinesis during microsporogenesis is compared with differences in aperture configuration, to assess the extent to which this appears to influence aperture arrangement. Triapertury in monocot pollen tends to fall into one or another of three situations: 1) it is the normal state, 2) it is fairly common, but pollen with more or less apertures also occur in the taxon or sample, 3) it is a rare, or abnormal state for pollen which usually has less than three apertures. The various forms of triaperturate pollen are described, as well as monosulcate pollen of the orchid genera Cypripedium and Paphiopedilum, often misinterpreted as tri-sulcate, and the unusual extended trichotomosulcate pollen of Agrostocrinum (Hemerocallidaceae). Monosulcy, trichotomosulcy, and zonasulcy, with unusual and rare exceptions of zonasulcy in the eudicots, are aperture states shared exclusively with the basal dicots. Furthermore, to some extent all have links with the triaperturate condition in monocots and basal dicotyledons. This is discussed, as well as the association of tripory with polypory in monocots and basal dicots. The fossil pollen record is considered.This paper is dedicated to Klaus Kubitzki in recognition, not only for his extensive contribution to systematic botany, but also for his firm belief that pollen characteristics contribute to a better understanding of plant systematics and evolution.     

Pollen morphology and systematics of Burseraceae

The Burseraceae are a medium‐sized family in which 18 genera are currently recognised. They are the subject of a long‐term project to describe the pollen morphology from light, scanning electron and transmission electron microscopy. The pollen morphology of tribe Protieae has been published, as well as an account of the pollen of the African taxa in the family. Pollen data for the other two tribes, Bursereae and Canarieae, are more or less complete. The pollen of all the genera have been examined, with the exception of the recently described Pseudodacryodes Pierlot for which, currently, there is no pollen material available. This paper summarises the results.

There is considerable variation in exine and aperture features between, and occasionally within, the genera and 14 major pollen types are defined, including two previously undescribed types: ‘Canarium oleiferum’ and ‘Canarium gracile’. The distribution of pollen characteristics throughout the family is compared with previously published tribal and subtribal groupings, as well as with current ideas of generic relationships from molecular analyses. Comparisons show notable congruence of pollen data with molecular data. To some extent pollen morphology is different for each of the subtribes. Nevertheless, there are some notable exceptions, for example, the pollen of Garuga and Boswellia are remarkably similar, although Garuga has been included, somewhat tenuously, in tribe Protieae, and Boswellia is included in tribe Bursereae, subtribe Boswelliinae. In a recent molecular tree Garuga and Boswellia appear to be closely related, and this supports the conclusion, based on several macromorphological characters as well as pollen, that Garuga should be transferred to tribe Bursereae.     

Ecophysiology of two solar tracking desert winter annuals

Summary The seasonal course of water relations in field populations of two leaf solar tracking desert winter annuals was examined. Measurements were made of leaf movements in relation to leaf conductance and water potential. Malvastrum rotundifolium maintained solar tracking movements up to the wilting point of the plant (-4 MPa). Lupinus arizonicus altered its morphology through paraheliotropic leaf movements as leaf water potentials declined to-1.8 MPa. Diurnal patterns of leaf conductance showed marked seasonal trends, with gas exchange activity being restricted to early morning hours as water availability declined. Studies of potted plants showed that L. arizonicus was not able to alter its osmotic potential in response to drought, while M. rotundifolium underwent a 1.86 MPa reduction in osmotic potential. The significance of the two contrasting patterns is discussed in terms of observed plant distribution and origin.     

Pollen–pistil interaction in protogyny and self-incompatibility system of Indian mustard (Brassica juncea (L.) Coss.)

The pollen morphology of two species of Drosera has been investigated by means of both light and electron microscopy. The apertures are situated proximally, a state rarely found in the pollen of Angiospermous plants. The pollen morphology of Aldrovanda, Dionea and Drosophyllum is compared.