Pollen morphology and localization of Ni in some Ni-hyperaccumulator taxa of Alyssum L. (Brassicaceae)

Pollen morphology of seven Alyssum L. taxa growing on serpentine soils in different places in the European Mediterranean macrobioclimate territory were studied, described and compared. Cluster analysis was performed to show similarity between species and their populations. The shape of the pollen grains varies among the species and among the grains within the same anther. The pollen grains are 3-colpate, prolate, with long and narrow colpi reaching the poles. The ornamentation of the exine varies from micro-reticulate to reticulate between the species. Pollen sterility/fertility was also calculated. The highest percentage of sterile pollen (73.76%) was calculated for Alyssum murale subsp. murale and the lowest (9.54%) for A. bertolonii subsp. bertolonii. All species are representatives of sect. Odontarrhena (C.A. Meyer) Koch well known as Ni-hyperaccumulators. Nickel and other elements present in pollen and stamen were studied by inductively coupled plasma-mass spectrometry. The stamen parts of all species were micromorphologically analyzed by scanning electron microscopy coupled to an energy-dispersive X-ray probe. Accumulation of Ni was detected in the stamens of all studied species and rarely in the pollen grains. The distribution patterns of Ni were similar among the species examined.     

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.     

Pollen morphology and its relation with meiotic irregularities in ten species of Campuloclinium (Eupatorieae,Asteraceae)

Pollen grains of ten species of Campuloclinium (Eupatorieae, Asteraceae) are described and illustrated using light and scanning electron microscopy. The species included in this study are C. burchelli, C. campuloclinioides, C. chlorolepis, C. hirsutum, C. irwinii, C. macrocephalum, C. megacephalum, C. parvulum, C. purpurascens and C. riedelli. Pollen grains of Campuloclinium are typically radially symmetric, echinate, tectate, oblate-spheroidal to prolate-spheroidal (P/E ratio: 0.94–1.10). Pollen is mostly triaperturate, but tetraaperturate or biaperturate pollen also occurs in some species. The pollen diameter was highly variable ranging from 10.54 µm to 36.18 μm. The significance of the variation in type and size of pollen is discussed in relation to diverse meiotic abnormalities and possible reproductive apomictic processes within the polyploid species.     

Pollen morphology of the East Asiatic genus Chelonopsis (Lamioideae: Lamiaceae) and allied genera,with reference to taxonomic implications and potential pollination ecology

Pollen grains of 15 taxa of the genus Chelonopsis (14 spp. and 1 variety) from China and Japan and 6 species of the closely related genera Bostrychanthera (1 species) and Gomphostemma (5 species) were examined by light and scanning electron microscopy. Of these, the pollen morphology of 18 taxa was studied for the first time. Pollen grains were found to be tricolpate with polar lengths of 20.8–30.0 μm and equatorial widths of 17.5–27.3 μm. The basic shape of the pollen in most taxa is subprolate or prolate-spheroidal, but spheroidal, subprolate-spheroidal, oblate-spheroidal, and prolate-subprolate grains are also found in some species. The surface is generally reticulate or suprareticulate in Chelonopsis and granulate in Bostrychanthera. In comparison with those of Chelonopsis and Bostrychanthera, the pollen grain surfaces of Gomphostemma are more diverse. In Chelonopsis, pollen is taxonomically useful at the sectional level, and some grains provide enough characters for species delimitation. The potential pollination ecology of cellular hairs on the anthers of Chelonopsis and Bostrychanthera is also briefly discussed.     

An Ultrastructural Study of Pollen Wall Ontogeny in Silene Pendula

Pollen of 41 species representing all seven genera of the Neottieae were examined by scanning electron microscopy. Except for Lecanorchis, the genera of the Neottieae constitute a natural group based on pollen morphology. Pollen occurs as single grains in the primitive species and in tetrads in the other species. Most grains are monoaperturate, porate or tenuate, and the tetrads often have irregularly shaped grains. Exine structure varies from tectate-perforate to semitectate. Lecanorchis is anomalous among the Neottieae in that it has 0–5, sunken, relatively small pores. Pollen morphology of this genus indicates that it is probably more closely related to the Gastrodieae than the Neottieae. There are at least four basic phyletic units in the Orchidaceae: the Neottioideae, Apostasioideae, Cypripedioideae, and Epidendroideae. These groups are distinguished by the presence of monads in at least their more primitive members and by their unique pollen types.     

Pollen size in Carex: The effect of different chemical treatments and mounting media

Pollen size and pollen aperture size for ten species of the genus Carex L., native to Estonia, have been measured using light microscopy. The species selected represent different sections of the genus, a range of habitats and different chromosome numbers. The effects of two basic chemical treatments, two mounting media and the effect of chemically induced dehydration with tertiary butyl alcohol (TBA) on the size of pollen grains were then recorded.

In general pollen size and pollen aperture size of the species examined is highly variable at both intraspecific and interspecific levels. Carex hirta has notably larger pollen grains than any of the other species investigated and, although correlations between size and chromosome number in the species examined are limited, it also has the highest chromosome number. Statistically significant size differences resulted from variations in chemical treatment, mounting media and tertiary butyl alcohol (TBA) induced dehydration. Acetolysed pollen grains are larger than potassium hydroxide (KOH) treated pollen grains. Pollen grains dehydrated after chemical treatment with TBA are larger than pollen grains not dehydrated. Pollen grains mounted in silicon oil are smaller than grains mounted in glycerine. But considering the great size variation of Carex pollen grains, the size changes caused by preparation procedures fall within the size variation range of the species examined.

All the samples contained a high number of deformed pollen grains and pollen grains with hardly distinguishable or no lateral apertures.     

Scanning and transmission electron microscopy related to immunochemical analysis of grass pollen

The exine stereostructure (scanning electron microscopy) and ultrastructure (transmission electron microscopy) of pollen of seven grass species, is related to the allergens extracted from these pollen grains. The heterogeneity of the allergens was studied by the immunoprint technique and revealed by labelling the binding of grass pollen sensitive patients IgE antibodies. Using patient sera recognizing a very restricted number of allergens, we showed that a group of pollen had a great number of allergens in common (Dactylis, Agrostis, Festuca, Lolium, Holcus) and, in decreasing cross reactivities order, we found Avena and, finally, Zea mays. The tectum stereostructure shows presence of insulae in all pollen grains except in Zea mays which has small isolated spinules. These insulae are separated by very wide and deep interinsular spaces in Avena sativa with connections between insulae. In the remaining species, no connections were seen between the insulae. These observations were in good correlation with the immunological cross-reactivity of the allergens present in the pollen. In all species, there are microperforations in the bottom of the interinsular spaces, which are the opening of the tectal microchannels.     

Pollen Morphology of Polemoniaceae in Relation to Systematics and Pollination Systems: Scanning Electron Microscopy

Representative pollen grains of each genus and section of the family Polemoniaceae were examined with scanning electron microscopy. Exine pattern diversity within the family is discussed in relation to pollination biology. Pollen data support some previously recognized relationships within the family; in other instances the use of pollen morphology suggests the institution of new associations. The value of pollen morphology as an index to possible phylogenetic interpretations within the Polemoniaceae is discussed.     

The comparative pollen morphology of genera Matricaria L. and Tripleurospemum Sch. Bip. (Asteraceae) in Turkey

Pollen morphology of four Matricaria species and 28 Tripleurospermum species was investigated with light microscopies (LM) and scanning electron microscopies (SEM). Pollen slides were prepared using Wodehouse technique. Measurements were based on 20 or more pollen grains per specimen. For SEM studies, dried pollen grains were transferred on aluminum stubs and coated with gold for 4 min in a sputter-coater. The pollen grains of Matricaria and Tripleurospermum are radially symmetric and isopolar. The pollen grains of the Matricaria are oblate-spheroidal with the polar axes 16.6–31.2 μm and the equatorial axes 18.7–23.9 μm. Tripleurospermum is oblate-spheroidal, suboblate and prolate-spheroidal with the polar axes 15.6–32.2 μm and the equatorial axes 17.7-38.5 μm. The pollen grains of Tripleurospermum are operculate and tricolporate. Matricaria is operculate and usually tricolporate or rarely syncolporate, tricolpate and tetracolporate. The pollen grain of both taxa shows echinate ornamentation. The spines are commonly conical with a broadened base and a tapered apical portion. The spine length varies between 1.8–4 μm in Tripleurospermum and 2.3–3.3 μm in Matricaria. The width of spines varies between 2.8–4.6 μm in Tripleurospermum and 2.4–3.6 μm in Matricaria. Inter-spinal area shows granulate–perforate, reticulate–perforate, rugulate–perforate ornamentations and the tectum surrounding the spine base is micro perforate. Overall exine thickness ranges from 2.8 to 4.8 μm in Tripleurospermum, 3.6 to 5.2 μm in Matricaria. Intine is thicker under pores in Tripleurospermum (0.3–0.62 μm) than in Matricaria (0.6–0.8 μm). Inter-spinal ornamentations, pollen shape and the numbers of perforations at the spin base have been observed as important morphological characters.     

Lessingianthus (Vernonieae–Asteraceae): generic and infrageneric relationships based on pollen morphology

Pollen morphology of 31 species of Lessingianthus was investigated in order to evaluate the generic and infrageneric relationships of Lessingianthus and related genera. Acetolyzed pollen grains were measured, described and illustrated using light microscopy. Non‐acetolyzed pollen grains were investigated using scanning electron microscopy. Pollen grains of Lessingianthus are isopolar monads, suboblate, oblate spheroidal or prolate spheroidal, lophate (30, 29 and 27 lacunae), with small or large polar area, tricolporate. Pollen grains with 30 lacunae occur in the majority of the species examined, and show three apertural, six abapertural, twelve parapertural, six interapertural and three equatorial lacunae. Pollen grains with 29 lacunae occur in L. desertorum, L. simplex and L. virgulatus and are characterized by three apertural, six abapertural, twelve parapertural, six interapertural and two polar lacunae, and by absence of equatorial lacunae. Pollen grains with 27 lacunae occur in L. adenophyllus and L. durus and are characterized by three apertural, six abapertural, twelve parapertural and six interapertural lacunae, but lack polar and equatorial lacunae. Species of Lessingianthus subgen. Lessingianthus, with few exceptions, have pollen grains with type B lophate pattern, which differs mostly in shape. Pollen grains of Lessingianthus subgenus Oligocephalus share a very similar pattern of 29 lacunae with those of Chrysolaena, supporting recently proposed taxonomic changes. Pollen grains with 27 regular lacunae occur in Lessingianthus durus and L. adenophyllus, but the first differ from the latter by having cross muri enclosing the apertural lacuna (type G pollen).     

POLLEN MORPHOLOGY OF AMPHIANTHUS,ARTANEMA, CURANGA,GLOSSOSTIGMA, AND PEPLIDIUM (SCROPHULARIACEAE-GRATIOLEAE)

Pollen of the scrophulariaceous genera Amphianthus, Artanema, Curanga, Glossostigma, and Peplidium was examined by light and scanning electron microscopy. All have single, isopolar, radially symmetrical pollen grains with equally spaced meridional colpi and columellate exines. Intergeneric differences are established mainly on the differential correlation of colpus number, colpus morphology, and sculpturing of the mesocolpium. The colpi vary in length and range in number from 3 to 6. The colpus membrane can be variously granular, verrucate, rugulate, or spinulose. The exine varies from semitectate and microreticulate or reticulate to tectate and sparsely perforate. It may be psilate or ornamented with supratectal processes ranging from small granules to relatively long spinules or bacules. All the genera examined, with the possible exception of Artanema vs. Amphianthus, are distinguished from one another by pollen morphology, and the grains of both Curanga and Glossostigma have morphotypes not previously reported in tribe Gratioleae. Final taxonomic assessment of the pollen data in the genera examined must await further comparative studies in the Gratioleae and other tribes, but the morphological diversity observed is clearly of potential significance in evaluating specialization levels and clarifying current conflicting interpretations of relationships in these taxa.     

In vitro allelopathic effects of pollen from three Hieracium species (Asteraceae) and pollen transfer to sympatric Fabaceae

Pollen allelopathy occurs when pollen toxins inhibit sexual reproduction in heterospecifics. To quantify pollen allelopathic effects in vitro, pollen of Hieracium aurantiacum, H. floribundum, and H. pratense was extracted with double distilled water into concentrations of 0 (control), 0.1, 1, 3, 5, 10, and 25 pollen grains/μl. A subset of these extracts was partitioned by ion-exchange chromatography into acidic, basic, and neutral fractions. Pollen from six sympatric species of Fabaceae (Lotus corniculatus, Medicago sativa, Trifolium hybridum, T. pratense, T. repens, Vicia cracca) and the species of Hieracium was germinated on agar media containing different extract concentrations. As extract concentrations from intact pollen or from acidic fractions increased, mean percent germination of pollen of all Fabaceae decreased nonlinearly. Extract concentrations of 0.1 grains/μl and above inhibited pollen germination in the Fabaceae. In no case was any Hieracium species affected, i.e., there was no autotoxicity. Similar results were obtained using plants from nine populations of H. floribundum and H. pratense across eastern Canada. Observation of floral visitors indicated that there were relatively few movements between Hieracium and the Fabaceae (about 15% of total visits). Hence there is limited opportunity for heterospecific pollen transfer. This was consistent with censuses of stigma, i.e., few pollen grains of Hieracium were found on stigma of the Fabaceae. Thus, pollen allelopathy in Hieracium is unlikely to affect reproductive success in these six species of Fabaceae.     

Pollen Morphology of the Aceraceae

Pollen of 40 Acer taxa and one species of Dipteronia were examined by light, scanning and transmission electron microscopy. Pollen grains in both genera are tricolpate or tricolporate of prolate to nearly spheroidal shape. Based on sexine pattern, four major pollen types were recognized and include striate grains, rugulose grains, microreticulate grains, and granular grains. Although the family appears to be rather stenopalynous, several useful taxonomic variations occur.     

Pollen characteristics of New Zealand Gnaphalieae (Compositae) and their taxonomic significance II. Tem

Pollen ultrastructure has been investigated in 35 taxa of Gnaphalieae (Compositae), predominantly from New Zealand. Pollen grains of all taxa examined are tectate‐columellate and caveate. The characters regarded as particularly distinctive include variability of columellar form and internal organisation of the columellae. The importance of pollen characters in the classification of the New Zealand Gnaphalieae is discussed. The species of Haastia, characterised by senecioid pollen and internal tecta, do not belong to the Gnaphalieae. In the species with helianthoid pollen and sub‐columellae five different columellae types can be distinguished.     

POLLEN MORPHOLOGY OF THE EUCHARIDEAE (AMARYLLIDACEAE)

Eucharis, Caliphruria, and Urceolina form a monophyletic group of petiolate-leaved, Neotropical Amaryllidaceae ecologically specialized to the understory of primary tropical rain forest below 2,000 m elevation. Pollen morphology of the three genera is surveyed. Pollen grains of all species of Eucharis, Caliphruria, and Urceolina are boat-shaped elliptic, monosulcate, heteropolar, and bilateral in symmetry. Exine sculpturing is semitectate-columellate and reticulate in all species examined. A transformation series in reticulum coarseness and pollen grain size is described. The large pollen grain with coarse reticulum of most Eucharis species is considered ancestral. The fine reticulation of Caliphruria is considered derived and the exine morphology of Urceolina is intermediate. Both of these genera have medium-sized pollen grains. Exine dimorphism common to all Urceolina, but rare in Eucharis and Caliphruria, may be symplesiomorphous among those taxa exhibiting this morphology. The three genera are largely uniform in pollen grain ultrastructure, with completely ektexinous exines. Pollen grain size in Eucharis is not closely correlated with style length. Several wide-ranging species show considerable intraspecific variation in pollen size. Parallelisms in pollen grain evolution among related tribes of Neotropical Amaryllidaceae are discussed.     

POLLEN MORPHOLOGY AND SYSTEMATIC RELATIONSHIPS AMONG NEW WORLD SPECIES IN TRIBE ANTIRRHINEAE (SCROPHULARIACEAE)

The morphology of mature pollen grains among 12 New World genera in tribe Antirrhineae has been examined with light and scanning electron microscopy. Pollen from 29 American species have mean polar diam that range from 17 to 26 μm, have a tectate structure with perforate, microreticulate, or reticulate surface pattern, and are subspheroidal to prolate, and trizonocolporate with fusiform or narrowly oblong colpi that are free or occasionally fused at the poles. Among the genera, pollen size is positively associated with style length but not haploid chromosome number. Three major morphological categories are recognized based on grain shape, exine structural pattern, and colpus shape. Two of these morphotypes each characterize individual genera (Mohavea, Linaria). The other morphological category includes ten New World genera and has been divided into three subcategories based on variation in lumina diam and intermittent occurrence of fused colpi. Only Antirrhinum and Pseudorontium have species or populations with pollen in more than one subcategory. Concordance of morphological, anatomical, chromosomal, and palynological data suggests that Linaria and Mohavea are best placed in separate subtribes from other native American genera. Compared to Old World taxa in tribe Antirrhineae, the most common pollen type (subspheroidal, microreticulate, apocolpate, fusiform colpi) may be the most primitive. Pollen grains with fused colpi (Antirrhinum p.p., Pseudorontium) and perforate (Mohavea) or reticulate (Holmgrenanthe) structural patterns probably represent derived types.     

Pollen in packrat middens

Fossil packrat middens are used to reconstruct late Quaternary environments in the arid Western U.S.A. Airborne pollen is contributed to middens both directly from the air, and through adherence to plant macrofossils. I examined the filtration of atmospheric pollen by Larrea tridentata leaves (resinous, with sparse recumbent hairs), Cercidium microphyllum twigs (glabrous with recumbent hairs) and Sphaeralcea ambigua leaves (covered with stellate hairs) and evaluated the potential biases of scavenged pollen on the interpretation of pollen records from middens. Pollen grains collected from the surfaces of the plants were most numerous during the spring when (airborne) pollen concentrations were high. Of the species investigated, the Sphaeralcea leaves filtered the greatest number of spring pollen grains from the air (3419 grains cm^?2); captured pollen was very low during other seasons. Sticky Larrea leaves continuously captured airborne pollen ( = 246 grains cm^?2). Pollen captured by smooth Cercidium was consistently low ( = 31 grains cm^?2). Only the spring pollen was filtered in sufficient numbers to obtain minimum pollen counts of 200 grains by all 3 taxa. The plants frequently captured greater proportions of their own pollen. Pollen content of packrat middens will reflect the season of plant macrofossil collection and the species composition of the plants incorporated.     

COMPARATIVE POLLEN MORPHOLOGY AND TAXONOMIC AFFINITIES IN CYCADALES

Scanning and transmission electron microscopy of pollen grains of 29 species, representing the ten extant genera of Cycadales, has provided valuable insight into their relationships. Pollen grains of these taxa are boat-shaped, monosulcate, and bilaterally symmetrical. They range from narrowly to widely elliptical or subcircular when viewed distally, and have an exine surface of psilate, foveolate, or fossulate. Pollen wall ultrastructure of Cycadales is typically tectate with alveolate∗∗∗spongy exine. The nexine is laminated in all genera. Nexine 1 (footlayer) is present in most species as a thin and often discontinuous layer. There is consistent variation in thickness of the sporoderm layers among the genera but relative uniformity within them. Pollen characteristics are well correlated with macro- and micromorphological features, chromosome numbers, geographical distribution, and postulated pollination mode. A close affinity between Encephalartos, Lepidozamia, and Macrozamia is recognized. Pollen characteristics of the genus Bowenia show some similarity with those of the latter group. Except for two species of Macrozamia which are narrowly elliptic, all of the genera have widely elliptic pollen and share a psilate exine surface and the thinnest sexine with nearly identical arrangement of alveoli. Pollen grains of the species in the genus Dioon exhibit a unique morphology but are more similar to Stangeria than they are to those of taxa in Zamiaceae. The circular outline of the grains and the foveolate exine surface are characters shared by these two genera, but several morphological features distinguish Dioon from Stangeria. Ceratozamia and Zamia share a widely elliptic shape, foveolate exine surface and nearly identical sexine, as well as morphological features and chromosome numbers. They differ from Microcycas in sexine thickness, gross morphology and chromosome numbers. The pollen grains of Cycas circinalis and C. revoluta differ in size and structure of the sexine from all other genera and from each other, substantiating their distinct subgeneric delimitations.     

Monophyly and generic relationships of polemoniaceae based on matK Sequences

Polemoniaceae are often considered a model family for studying evolutionary processes, yet a reliable phylogeny for the family is only now beginning to emerge. To test the monophyly of this family and to elucidate intergeneric relationships, we employed comparative sequencing of the chloroplast gene matK. Parsimony analysis of matK sequences representing 18 genera of Polemoniaceae and nine families from Asteridae sensu lato places Polemoniaceae apart from Solanaceae near Fouquieriaceae, Ericaceae, Sarraceniaceae, and Diapensiaceae. Both this and a subsequent analysis of 59 species of Polemoniaceae indicate that Cobaea is derived from within Polemoniaceae, rather than being the sister to Polemoniaceae as suggested by some authors. The tropical genera Bonplandia, Cantua, and Cobaea form a clade, and the remaining, primarily temperate genera, excluding Acanthogilia, form a second monophyletic group. Acanthogilia is placed ambiguously as sister to either the tropical or temperate groups depending on the location of the root for Polemoniaceae. Within the temperate lineage, Polemonium is sister to three large clades: a well-supported clade comprising Phlox, Gymnosteris, Linanthus, Leptodactylon, and Gilia filiformis; a moderately well-supported clade comprising Allophyllum, Collomia, Navarretia, and several species of Gilia; and a weakly supported clade comprising Eriastrum, Ipomopsis, Langloisia, Loeseliastrum, Loeselia, and several species of Gilia. In addition to revealing the extreme polyphyly of Gilia, this analysis suggests that Ipomopsis and Linanthus are also polyphyletic.     

Pollen morphology of the genus Gagea (Liliaceae) in Iran

Pollen grains of 26 species of the genus Gagea distributed in Iran were examined by light and scanning electron microscopy. Detailed pollen morphological characteristics are given for these species. Among the studied species, the newly described G. iranica together with G. olgae and G. graminifolia possess the smallest pollen grains, and the widely distributed G. lutea the largest ones. Our studies show that the sculpturing of exine provides valuable characters for separating the species, sometimes even for closely related ones, and delimitation of natural groups within the genus. The exine of the genus Gagea is in most cases perforated upon tectum or rarely tectate-columellate. The muri are solid or structured, compound, simpli-, dupli- or pluricolumellate. It seems that the structure of muri is very important in recognizing natural groups within the genus. Tectal perforations vary from <0.2 to 2.0 μm in diameter among the studied species. Regarding sculpturing of the exine in proximal face, four basic types of pollen grains can be distinguished: reticulate, microreticulate, foveolate and perforate. Within the reticulate type there is sufficient variation in exine structure at distal face to describe three subtypes: reticulate, microreticulate and perforate. A diagnostic key is given for all studied taxa based on palynomorphological characters. For a limited number of populations of selected Iranian species of Gagea, further aspects of pollen biology were studied. It seems that populations with ploidy levels other than diploidy, show a low percentage of pollen fertility. Moreover, the rate of pollen fertility is correlated with the manner of the reproduction in certain species.