Exine Morphology Research Articles

Variability of eight Algerian oleaster ecotypes (Olea europaea subsp. europaea var. sylvestris [Mill.] Lehr): pollen and exine morphology in relation to geo-climatic effect

Pollen characters of the Algerian oleaster (Olea europaea subsp. europaea var. sylvestris [Mill.] Lehr) from eight ecotypes were analysed to evaluate the geo-climatic effect of their environment. Samples were collected along an altitudinal gradient from western to central Algeria. Eighteen morphological characters of the pollen grains were studied using scanning electron microscopy (SEM). The results show significant inter-populations variability. The geo-climatic conditions, duration and timing of dry periods vary from one area to another. Depending on the area, the length of the dry period (P p ≤ 2T) coincides more or less with anthesis periods. No significant geo-climatic effects on exine parameters were detected, except for lumina density (LD) and mean lumina diameter (Lm). However, polar axis (P), pollen size index (PSI) and pollen colpis length (PCL) were found to be related to latitude, longitude and temperature. LD and Lm were strongly linked to the pollen parameters, resulting in variation in pollen shape and size. Depending on the geo-climatic conditions, three morphotypes appear. The morphotype from a site with high temperature, low humidity associated with a long dry period is characterised by small pollen size, low lumina surface area and high lumina density/100 μm2 and vice versa. The results indicate that the exine has played an important role in the environmental adaption in these wild populations.

A contribution to the knowledge of the exine, with special reference to the ultrastructure, in subtribe Ecliptinae (Heliantheae, Asteraceae)

The exine morphology, with emphasis on the ultrastructure, of six genera and species of Ecliptinae was studied with transmission electron microscopy and scanning electron microscopy. A caveate exine with a single layer of columellae and predominantly circular to sub-circular internal foramina (Helianthoid pattern of structure) is present in all the studied taxa and most probably in all the Ecliptinae. The morphologies of the internal foramina and foot layer are consistent within the Ecliptinae, and their potential taxonomic and phylogenetic relevance was discussed. The existence, for almost all the investigated characters and ratios, of a continuous gradient among the taxa, exists in the wedelioid group and constitutes a quite well defined parallelism between the exine data and those of the major clade of Ecliptinae (wedelioid group). The exine sculpture of the worldwide weed Eclipta prostrata (L.) L. presents some variation, which is, most probably, correlated to the existence of geographical clines and/or variations in its chromosome number. A mesoaperture concerning the foot layer and the upper part of the endexine exists in all the taxa studied and, presumably, in all the Ecliptinae, probably constituting a synapomorphy for all the Asteroideae and possibly for all the Asteraceae.

Morphology and anatomy of the exine in Saxifraga (Saxifragaceae)

Details of exine morphology (SEM studies of 132 species) and anatomy (TEM studies of 25 species) of Saxifraga are reported. The variation observed was compared with that found in an earlier survey. We suggest modifications to known types and subtypes and the addition of new ones, making a total of nine exine types and subtypes in Saxifraga. Taxonomic conclusions include the following. A novel exine type (Type 2.3), in which the single tectum has numerous microchannels, is a putative synapomorphy for sects. Heterisia and Irregulares. At least three species from sect. Ciliatae, viz., S. lychnitis, S. oresbia from ser. Lychnitidae, and S. nigroglandulifera from ser. Nutantes, have a novel type with a perforate-reticulate or perforate-rugulate tectum. Species from the rest of the section are uniformly finely striate. Section Saxifraga has Type 2.1, with a single tectum, Type 4.3, with a double tectum, and Type 2.2, which is intermediate to various extents. The origin of Types 2.1 and 2.2 from Type 4.3 is suggested. Within sect. Saxifraga subsect. Triplinervium, S. wahlenbergii is unique in possessing pollen with a secondary tectum (Type 4.3), resembling the exine of S. androsacea in subsect. Holophyllae. On this and other grounds, we support the transference of S. wahlenbergii to the latter subsection. Himalayan species with opposite rather than alternate leaves that were formerly assigned to sect. Porphyrion subsect. Oppositifoliae, have exines with supratectal ornamentation similar to that in subsect. Kabschia; in this respect they are unlike the European species with opposite leaves, which lack this ornamentation. Among the species with chalk-glands, exines lacking supratectal ornamentation are restricted to European species, viz. those in sect. Porphyrion subsects. Engleria and Oppositifoliae, and S. florulenta, offering morphological support for the transfer of the latter species to sect. Porphyrion. Saxifragella is recognised as a new section of the genus.

The utility of the morphological variation of pollen for resolving the evolutionary history ofBillia(subfam. Hippocastanoideae, Sapindaceae)

AbstractIn this study, we examined the utility of pollen morphology for resolving questions about the evolutionary history ofBillia, which is a poorly known genus of Neotropical trees.Billiahas been traditionally circumscribed with two species and treated as sister toAesculusL. However, the number of species inBilliais uncertain, because the genus exhibits abundant morphological diversity but little discontinuous variation. Therefore,Billiamay be monotypic and highly polymorphic, or it may have two species with blurred boundaries due to incipient speciation and/or hybridization. Moreover, one recent molecular phylogenetic study showsBillianested withinAesculus. Our work sought to address the following questions: (i) Are there discontinuities in the pollen ofBilliathat may suggest species boundaries? (ii) Does the pollen ofBilliashow evidence for inter‐specific hybridization? (iii) Do the exine morphology and size of pollen inBilliadiffer from those inAesculus? Our results from scanning electron microscopy showed that pollen exine morphology is not taxonomically informative inBilliabut that there are significant differences in pollen size between red‐ and white‐flowered individuals. Thus, our pollen data support the utility of flower color inBilliafor species delimitation. Our assessments of pollen viability do not support hybridization in the genus, but cannot be used to rule it out. Finally, pollen exine morphology may lend some support to an evolutionary origin ofBilliawithin eastern North AmericanAesculus. In contrast, data on pollen size suggest thatBilliamay belong in a topological position outside ofAesculus.

Analysis on Composition of Pollen Exine and Pollen Morphology in Five Species of Gymnosperm

Fourier transform infrared( FTIR) spectroscopy was used to study the composition of pollen exine in five species of gymnosperm,including Ginkgo biloba L.,Abies firma Sieb et Zucc.,Cedrus deodara( Roxb.) G. Don,Cunninghamia lanceolata( Lamb.) Hook,and Cryptomeria japonica( L. f.) D. DON. The results showed that the infrared spectra of these pollen exines are mainly composed of the absorption bands of protein, lipids and polysaccharides,however,there were different components of pollen exine in these 5 species of gymnosperm. For example,there was much protein in pollen exine of G. biloba; rich lipids in pollen exine of Sonko; and polysaccharides in pollen exine of Taxodiaceae. In addition,there are significant differences in the spectra of different genus. Using scanning electron microscope,we observed that the pollens of C. deodara and A. firma are big in size,with two sacs. In contrast,the pollens of the other three species are small in size, without sacs. The surface of pollen exine in C. japonica and C. lanceolata showes orbicules,but that of C. deodara( Roxb.) G. Don and A. firma Sieb et Zucc shows the ornamentation of microgranulates with rough surfaceand smooth surface showing apertures.

Understanding the Phylomorphological Implications of Pollinia from <i>Dendrobium</i> (Orchidaceae)

We aim to evaluate the evolutionary trends of pollen ultra-structures and microstructures in the light of molecular phylogeny, and to test whether pollen micromorphology is a predictor of interspecific phylogenetic relationship or a consequence of ecological influences. Using scanning electron microscopy pollinia micromorphologies of 18 species of the genus Dendrobium were comprehensively examined. A phylogenetic tree from ribosomal-ITS2 sequences was constructed reflecting molecular phylogeny. In result, two major clusters were identified representing the sections Aporum, Formoase Dendrobium and Holochrysa. The section Dendrobium could be further classified, for the first time, into two clades sharing the same root of origin. Variations in the shape of pollinia were distinct and consistent constituting six novel groups. Other qualitative/quantitative keys to pollinia showed congruence with molecular phylogeny and supported the correlated evolution of these traits. Concurrently pollen sculpturing also showed large variation in exine morphology (rugular/psilate to psilate-scabrate/rugulate-scabrate) providing explicit clues for phylogenetic trend of exine evolution. For the characteristic sculpturing on the pollinia surface, a simple version of pre-pattern model is also hypothesized for deeper insight into pattern formation in other biological systems. Results indicated that distinct groups of Dendrobium species have parallel and independent evolution accompanied with genetic changes occurred during species diversification. Thus pollen micromorphology is a good candidate for inferring the genetic relationship at inter-specific level having phylogenetic implications even using abundant palynological records.

Palynomorphological characterization of some species of Ficus L. from Pakistan

The present study was confined to pollen morphology and pollen fertility estimation using a taxonomic description of 11 species of genus Ficus family Moraceae. The species wereFicus bengalensis L, Ficus microcarpa L.f., Ficus palmata Forrsk., Ficus religiosa L., Ficus lacor Ham., Ficus pumila L., Ficus hispida L.f., Ficus sarmentosa Buch.Ham, Ficus auriculata Wall., Ficus virens Dryand. and Ficus racemosa Roxb. A palynomorphic study of the following species was conducted for the first time not only in Asia, but worldwide. As such, no published details were available for such comprehensive morphopalynological studies of the following species of genus Ficus L. It was found that pollen characters (that is, shape, surface of exine and pollen morphology) were considered as important characters and were used as tools in the taxonomy of these species. In the present research, the highest (97.82%) value was observed in F. palmata Forrsk. (Table 1) and the lowest (60%) was observed in F. bengalensis L. The present study shows that the flora of the selected species is a stable one. However, genetic diversity and molecular studies may also be helpful in this regard. Key words: Ficus, palynology, pollen fertility.

Palynology of the Genus Stachytarpheta Vahl. (Verbenaceae)

The exine morphology of pollen grains of Stachytarpheta indica (Linn.) Vahl, Stachytarpheta cayennensis (Rich.) Vahl and Stachytarpheta angustifolia (Mill.) Vahl is reported. This study was carried out with a light microscope. Pollen grains from fresh anthers were collected and aceolysed. Statistical analysis used to analyse the data collected include cluster analysis, correlation analysis, similarity and distance indices. The pollen grains are spheroidal to oblate to sub-oblate in shape. They are aperturate, both colpate and porate. Tricolpate types occur most frequently, acolpate, monocolpate, bicolpate and tetracolpate types less frequently. The multicolpate and multiporate attributes in all the species indicate that the genus is not primitive in evolutionary history and this species probably, evolved around in the same time. According to the size, the pollen grains of the genus falls into groups permagna (pollen diameter 100-200 μm) and giganta (pollen diameter greater than 200 μm). S. cayennensis and S. anguistifolia belong to group permagna and S. indica only in the group giganta. This separates S. indica from the other two species. The large pollen grain size in the genus clearly supports the fact that the flowers in the genus are more insect-and-bird pollinated than wind pollinated. The similarity and distance indices of the species showed that S. cayennensis and S. angustifolia are the closest. S. indica is closer to S. angustifolia but farther from S. cayennensis.

Evaluation of pollen morphology as a taxonomic character for generic delimitation in Scilla s.l. (Hyacinthaceae)

Scilla L. s.l. (Hyacinthaceae) comprises about 100 species distributed in south Europe, the Mediterranean region, and central and western Asia with 10 species reported from Iran.However, according to recent studies based on molecular data Scilla s.l. is not monophyletic and should be divided into several smaller genera, i.e. Fessia Speta, Othocallis Salisb., Pfosseria Speta, Prospero Salisb., Scilla s.s. and Zagrosia Speta.In the present study the pollen grains of 13 species representing six segregate genera within Scilla s.l. were studied to evaluate the taxonomic value of pollen characters for generic delimitation. Pollen grains of all examined species were found to be monosulcate, prolate or sub‐prolate and heteropolar. Three different types of exine sculpturing were recognized: fossulate, perforate–reticulate and perforate.In Prospero autumnale (=Scilla autumnalis) pollen exine sculpturing is fossulate. In Othocallis armena, O. mischtschenkoana, O. rosenii and O. siberica (=Scilla armena, S. mischtschenkoana, S. rosenii and S. siberica) exine sculpturing is perforate–reticulate with mainly large perforations surrounded by smaller ones. In Fessia gorganica, F. greilhuberi, F. hohenakeri, F. khorassanica and F. raewskiana (=S. gorganica, S. greilhuberi, S. hohenakeri, S. khorassanica and S. raewskiana) the exine is perforate with rather uniform perforation. Zagrosia persica (=S. persica) has the same exine type as Fessia spp. In Pfosseria, the exine is perforate with linear and circular perforations. Scilla s.s. has a perforate exine, but the perforations are not uniform and their size and shape are variable.Our results are generally congruent with the circumscription of the new genera previously included in Scilla s.l. and show that pollen exine morphology is useful as an additional taxonomic character for the delimitation these segregate genera.

The conserved nature and taxonomic utility of pollen morphology in Cantua (Polemoniaceae)

Pollen exine morphology of nine of the ten species of Cantua (Polemoniaceae) is examined using light and scanning electron microscopy. A total of 28 specimens of C. bicolor, C. buxifolia, C. candelilla, C. cuzcoensis, C. flexuosa, C. pyrifolia, C. quercifolia, C. volcanica, and an as yet undescribed species (Cantua sp. nov.) are examined using either fresh or herbarium material. Pollen grains are found to be spheroidal, pantoporate, and quite large; mean diameter varies from 62 to 87 μm. Mean number of pores varies from 4.5 to 21.2 and mean pore size varies from 4.86 to 12.40 μm. Pollen grains of all species have insulate semitectate sexines. This feature distinguishes the pollen of Cantua species from the remainder of the Polemoniaceae. Insulae are evenly distributed over the surface of the pollen grain, with the exception of C. flexuosa and occasionally C. buxifolia, where insulae are more sparsely and haphazardly distributed. The majority of the species examined have irregularly shaped tectal insulae, with the exception of the large rounded insulae in C. quercifolia and the elongated narrow insulae in C. volcanica. Cantua quercifolia and C. volcanica have supratectal verrucae, a possible synapomorphy. In comparison to close relatives, the pollen grains of Cantua are evolutionarily conserved, and show little variation among species.

509 A Glycine-rich Protein from Tomato Involved in Pollen Wall Formation

The sporophytic tissue of the anther and, in particular, the tapetum, a cell layer surrounding the pollen sac, is know to be essential for the production of pollen. The isolation and characterization of the gene 92B from tomato that encodes an extracellular glycine rich protein (GRP) has been used to further elucidate the role of the tapetum in pollen development. RNA from the 92B gene accumulates exclusively in the tapetum. Polyclonal antibodies raised against the 92B GRP detect four proteins in stamens with microspores beginning meiosis. In pollen extracts, the antibodies detect a single protein. Expression of the tomato 92B gene in transgenic tobacco indicates that the four protein products are derived from only the 92B gene. The 92B GRP is localized to the tapetum, the callose wall of microspore mother cells, the exine (outer wall) of mature pollen, and orbicules. Orbicules are globular bodies derived from tapetal material that form on the tapetum wall and line the exterior of the pollen sac. Expression of 92B antisense RNA resulted in a significant decrease of 92B RNA and protein levels in transgenic tomatoes. This reduction was correlated with a decrease in pollen germination and an abnormal exine morphology. The function of the 92B protein in pollen development and function will be discussed.

Pollen morphology of Adenandra (Rutaceae: Diosminae) and its taxonomic implications

The pollen morphology of Adenandra Willd. (Rutaceae: Diosminae) was investigated to determine its taxonomic significance. Pollen of 27 of the 30 infrageneric taxa (representing 16 of the 18 species) was investigated by LM, SEM and TEM. Adenandra differs from all other Diosminae in having 4-colporate rather than 3-colporate pollen grains. This supports the alleged monophyletic status of the genus. Exine morphology and structure, however, is extremely diverse considering the size of the genus, with eight distinct pollen types and four subtypes being discerned. In some members the grains have uniform macroreticulate, striate or striato-reticulate sculpturing, whereas in others the poles have striate, striato-reticulate or reticulate-perforate sculpturing with various types of reticulate or rugulate sculpturing at the mesocolpia. Taxonomic groupings revealed by the pollen characters suggest elationships between taxa that were not previously apparent. It is suggested that evolutionary diversification among species of Adenandra is often more strikingly reflected by pollen morphology than by macromorphology, hence the eurypalynous state of the genus.

Developmental stages of the pollen wall and tapetum in some Crocus species

The developmental stages of the pollen wall and tapetum, together with exine morphology were studied in a number of Crocus species, by light and scanning electron microscopy. Gametogenesis was characterized by: 1) development of a thick intine, 2) single mitosis, and 3) terminal amylolysis. The tapetum was of the secretory type. In C. cartwrightianus cv. albus, abnormal sporogenesis and gametogenesis produced vacuolate pollen grains with a reduced-or no intine layer, and rich with starch granules; the tapetum was either of the parietal-or amoeboid type. The exine was echinate and the pollen grains had different types of aperture: furrows, colpi or pores. The ornamentation varied from microreticulate to irregularly perforate. The exine framework was overlaid by a pellicle resistant to chloroform-carbon disulphide, on which a layer of pollenkitt was deposited. The results are discussed from both cytological and evolutionary viewpoints.

Polarity, aperture condition and germination in pollen grains ofEphedra (Gnetales)

Pollen grain polarity, aperture condition and pollen tube formation were examined inEphedra americana, E. foliata, E. rupestris, E. distachya, andE. fragilis using LM, SEM and TEM. In the characteristic oblate pollen, as seen in situ in the tetrad configuration, the polar axis is the minor one and the equatorial plane runs between the two narrow ends of the microspore. The intine is thick in fresh fixed mature pollen but we have seen no indication of regions having an exceptionally thick intine that could be considered associated with an aperture or apertures. About three minutes after transferring fresh pollen to the germinating medium the ridged exine splits and twists away from the intine and its enclosed protoplast. The shed exine spreads out and curls into a scroll-like configuration that is as distinctive as that of the pollen shape had been but now having the ridges and valleys perpendicular to the long axis. The pollen tube develops, in our experience with more than a hundred germinating pollen grains, near one of the narrow tips of the pollen grain's equatorial plane. The location of the pollen tube initiation probably is related to the position of the tube cell nucleus. The pollen tube starts to grow about one hour after the exine was shed. The pollen tube emerges close to the narrow end (equator) of the gametophyte. This end emerged first as the exine is shed and is opposite to the prothallial cells. The stout pollen tube is c. 10µm in diameter grown in vitro on agar. In our germination medium the stout tube continued to elongate for about 24 hours reaching a length of c. 100 µm. With respect to exine morphology the aperture condition could be considered as inaperturate. The pollen tube, however, is formed in a germination area near one end of the exineless gametophyte.

Confocal imaging of exine as a tool for grass pollen analysis

A new method which utilises confocal optical imaging has been developed which can be expected to improve grass pollen analysis. Confocal microscopy, in reflection mode, was used to examine the exine morphology of unacetolysed pollen grains from the following species of common wild grasses: Paspalum dilatatum, Setaria gracilis, Bromus catharticus, Daclylis glomerata, Lolium perenne, Poa pratensis, and Phalaris aquatica. Variations in the surface texture patterns, similar to those hitherto only seen by scanning electron microscopy, were visualised. In contrast to the latter method, specimen preparation for this confocal microscopy based technique was characterised by its simplicity, permitting the use of fresh and chemically untreated pollen grains. This confocal imaging technique, with its capacity for optical sectioning of specimens, offered the additional advantage of allowing the examination of the sub‐surface exine layers as well as the surface morphology of the pollen grains. Furthermore, three‐dimensional reconstruction of these optical sections enabled visualisation of the identified sculptural and structural exine elements and layers. A number of differences in these patterns were found, which indicate that confocal microscopy, in combination with image analysis, may enable finer taxonomic distinctions to be made than those currently provided by other light microscope based methods.

Pollen morphology in Psychotria (Rubiaceae, Rubioideae, Psychotrieae) and its taxonomic significance. A preliminary survey

The pollen morphology in 168 species of Psychotria (Rubiaceae, Rubiodeae, Psychotrieae) has been investigated using light microscopy and, for 61 of the speices, scanning electron microscopy. Transmission electron microscopical studies have been carried out for seven of the species. Psychorria is very heterogeneoous pollen morphologically and pollen grain characteristics cannot be used for the delimination of the basis of aperture morphology, thickness of exine, size of lumina, muri, columellae and bacula, and sculpture. A key to the identificantion of the pollen types is presented and all types are issstrated. The pollen grains in Psychotria are usually 3–to 5colporte, 3‐to 5‐colpate or inapertuarate, rarely 2–4‐or 5‐porate, and have an exine that vanes widely in thickness. The sexine is reticulate, microreticulate, tectate‐perforate, rugulate or intectate, and smooth or sculptured. Exine morphology presents important characters for the taxonomic subdivision of Psychotria. Previous intrageneric classifications are in part supported by pollen morphology, but contradictions between this and other sets of charactes, such as inflorescence features. are common.

The “Zavada hypothesis”: a rebuttal rebutted

SummaryGibbs, P.: The “Zavada hypothesis”: a rebuttal rebutted. ‐ Taxon 40: 583–595. 1991. ‐ISSN 0040‐0262.The Zavada hypothesis, that there is a correlation between the various types of self‐incompatibility mechanisms found in angiosperms and details of pollen exine sculpturing, is addressed again. In the light of a recent further defence of the hypothesis, some errors in the original data on which it was based are considered, and some criticisms by Zavada of a different data base are discussed.

Pollen morphology of North American species of Antennaria (Asteraceae: Inuleae)

The pollen of 90 individuals representing 28 species and subspecies in the genus Antennaria is described through the use of light and scanning electron microscopy. Two morphological groupings separated on the basis of exine morphology are evident from cluster analysis. One group consists of those species and subspecies in which the exine is perforate and the other group consists of those individuals in which the exine is not perforate (perforate-reticulate or striate-perforate-reticulate). These two pollen morphological groups do not correspond with previously defined groupings based on morphology or cytogenetics. Both large (> 19 μm in diameter) and small pollen grains occur in each of the cluster groups. Similarly, both long- (> 2 μm) and short-spined individuals occur in each of the cluster groups. Used in combination, these characters do however exhibit some sectional affinities. Section Alpinae is characterized by pollen grains with long spines. Section Dioicae is characterized by small pollen grains. Section Plantaginifoliae is characterized by large pollen grains with long spines. Species included in sections other than these are not consistent in their pollen morphology. The pollen groups recognized in this preliminary study form a basis for future studies at the geographic or population level.

Pollen morphology of the Embothrieae (Proteaceae) II. Embothriinae (Embothrium, Oreocallis, Telopea)

Abstract This is the second of two papers dealing with pollen morphology and evolution within the tribe Embothrieae. The present paper examines pollen of the subtribe Embothriinae, Embothrium (1 sp.), Oreocallis (6 spp.), Telopea (4 spp.)) in the light microscope and scanning and transmission electron microscopes. Pollen is large-sized, oblate to suboblate to oblate-spheroidal, foveolate to microreticulate to spinulate with a predominantly granular exine and simple aperture morphology. The Embothriinae are palynologically heterogeneous with both Oreocallis and Telopea each exhibiting two distinct pollen types. Pollen of New World Oreocallis (O. grandiflora, O. mucronala) and the Old World O. pinnata are closer to the Old World Telopea (excluding T. speciosissima) than to other Old World Oreocallis (O. sp. nov. O. brachycarpa, O. wickhamii). Within this complex, O. pinnata occupies an intermediate position between Oreocallis and Telopea. Despite the uniformly biporate condition in Embothrium, other pollen ...

Scanning electron microscopy of some critical bearded Irises polle preliminary observations

Summary In the course of the current studies on the cytotaxonomy of the genus Iris L. Subgenus Iris Section Iris (MATHEW 1981), we have extended our investigations to include the SEM of pollen exine morphology in the effort to obtain further taxonomic markers to clarify several problems of determination in some bearded groups mainly of Italian provenance. This preliminary study describes the micromorphology of the pollen in nine bearded Irises followed by a discussion and a synthesis of the related evolution hypothesis examined under different points of view.