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.     

Molecular evidence for hybridization and introgression in the neotropical coastal desert-endemic Palaua (Malveae, Malvaceae)

Recent years have seen an increasing awareness of the importance of hybridization and introgression in plant evolution. Both processes were also invoked to have had a strong impact in the evolution of Palaua, based on morphological intermediacy. Here, we used nuclear ITS and cellulose synthase DNA sequences to assess previous phylogenetic hypotheses and to uncover previously undescribed reticulate evolution in Palaua. Both nuclear regions recovered largely the same reticulate pattern, showing that interspecific crosses occurred between distantly related species of the Dissecta and Integrifolia clade. Hybridization between species occurred only in a narrow contact zone. Moreover, many sequences of Palaua dissecta were placed in the strongly divergent Integrifolia clade, a pattern that is best explained by introgression. These results support our view that the strong interannual fluctuations of humidity and habitat expansion provide opportunities for the isolation of taxa, establishment of hybrid species, and for introgression between incompletely reproductively isolated taxa following recurrent contact.     

Variation of pollen and ovule parameters among different ploidy levels ofCorydalis (Fumariaceae)

The size and number of pollen grains and ovules are compared between 20 populations of different ploidy levels in two self-incompatible species ofCorydalis (Fumariaceae), to test the presence of ploidy-related variation in these reproductive characters. In both species, higher ploidy levels are associated with larger pollen grains, ovules and corolla, but the number of pollen grains and ovules are not different between ploidy levels. The investment per flower is consequently larger at higher ploidy levels, but the flower number per individual is lower, suggesting that the mode of partition of the investment for sexual reproduction varies between different ploidy levels. InC. orthoceras, sex allocation estimated by pollen:ovule ratios in number and volume is more female-biased in polyploids than in diploids. In spite of these variations, the characters studied can not be used as indicators of ploidy level due to the large overlaps between the ploidy levels.     

The metareticulate pollen morphology of Alternanthera Forssk. (Gomphrenoideae,Amaranthaceae) and its taxonomic implications

Alternanthera (Amaranthaceae) is a diverse genus largely restricted to the American Tropics that belongs to the alternantheroid clade containing C₄ and C₃–C₄ intermediate species. This research focuses on the study of pollen characters by studying 13 species, representatives of the two major clades and subclades of Alternanthera. General palynological comparisons were conducted with light microscopy (LM), scanning electron microscopy (SEM) and with confocal laser scanning microscopy (CLSM) for exine ultrastructure. Twenty-five characters were measured and described for Alternanthera and among these, 14 pollen characters were used to discriminate pollen groups using cluster analysis and canonical analysis of principal coordinates (CAP). Pollen form and ornamentation, pores number, spines length, number of ektexinous bodies and nanospines on the ektexinous bodies on pore membranes, arrangement of nanopores and spines on structural elements, and metareticula form were taxonomically important and therefore used to construct the first palynological key to the alternantheroid clade species. Our study indicates that the seemingly subtle morphological variation of pollen is useful for recognising three main pollen types within Alternanthera. The much needed palynological terminology for describing the mesoporium in the metareticulate pollen of Amaranthaceae is provided.     

Pollen grain morphology supports the taxonomical discrimination of Mediterranean oaks (Quercus,Fagaceae)

The exine architecture and some quantitative parameters (polar and equatorial axes and their ratio) of pollen grains allow a clear discrimination between groups of Mediterranean oak species. For the differentiation of species within groups only the quoted parameters prove useful.     

Comparative pollen morphology of Glechoma and Marmoritis(Nepetinae,Lamiaceae)

The pollen morphology of 13 taxa(34 specimens)of the genera Glechoma L.,and Marmoritis Benth.was investigated in detail using light,scanning electron,and transmission electron microscopy.Pollen grains of all studied taxa are small to large in size(P = 32.5-60.4μm,E = 20.2-50.5μm),prolate-spheroidal to prolate in shape and mostly hexacolpate(the amb more or less circular or rarely ellipsoid)with granular membranes.The sexine ornamentation of Glechoma is bireticulate; the muri of the primary reticulum are irregularly circled,and lumen size is short.In contrast,the sexine surfaces of the Marmoritis pollen tend to more elongate or wider at the muri of the primary reticulum than those of the Glechoma.The pollen wall stratification of selected taxa(three from Glechoma and one from Marmoritis)is characterized by unbranched columellae,and continuous or distinctly discontinuous endexine based on transmission electron microscopy observation.The results of Glechoma and Marmoritis reveal rather similar pollen morphological features,however,fine details of sexine ornamentation are characteristic to differentiate the pollen taxa.Although these differences may be useful in establishing the taxonomic boundary between two genera,they are too weak to segregate diagnostic characters.     

Effects of sequential pollination on the success of "fast" and "slow" pollen donors in Hibiscus moscheutos (Malvaceae)

Competition among pollen grains for the chance to fertilize ovules typically involves two stages: arrival times on stigmas and/or the growth of pollen tubes through styles. In a previous study of Hibiscus moscheutos, we found that individual pollen donors often differed in pollen tube competitive ability. Here we determined whether short delays in pollen arrival time altered the average success of "fast" and "slow" pollen donors when both types of pollen experienced the same delays. Hand-pollination experiments were carried out using four pairs of pollen donors that differed in competitive ability. We allowed delays of 15 or 30 min between the first and second pollen donor and then determined seed paternity using allozyme markers. The second donor typically sired fewer seeds than pollen that arrived earlier, but, contrary to expectation, "faster" pollen did not always sire significantly more seeds than "slower" pollen when each was applied after delays of the same duration. In two of the four pairs of donors, differences that were seen following simultaneous pollinations disappeared when each type of pollen was applied following identical delays of 15 or 30 min. This unexpected response suggests that the dynamics of pollen tube competition are more complex than anticipated.     

Effects of soil phosphorus on pollen production,pollen size,pollen phosphorus content,and the ability to sire seeds in Cucurbita pepo (Cucurbitaceae)

To determine the effects of soil phosphorus on pollen production, pollen grain size, phosphate concentration per pollen grain, and the siring ability of pollen, two cultivars of the common zucchini (Cucurbita pepo) were grown under two soil phosphorus conditions in an experimental garden. Overall, soil phosphorus availability had a significant effect on reproductive output through the female function and on traits affecting the male function of plants (staminate flower production, pollen production per flower, and pollen grain size). In addition, pollen produced by plants in the high phosphorus soils had a higher phosphate concentration than pollen produced by plants in the low phosphorus soils. A pollen mixture experiment revealed that pollen produced by plants in the high phosphorus treatment sired significantly more seeds than pollen produced by plants in the low phosphorus treatment. This study showed that growing conditions such as soil phosphorus can influence the size of a pollen grain and its chemical composition, which, in turn, can affect its ability to sire mature seeds.     

Enantiostyly in Chamaecrista ramosa (Fabaceae‐Caesalpinioideae): floral morphology,pollen transfer dynamics and breeding system

Enantiostyly is a form of reciprocal herkogamy, in which floral morphs present reciprocal differences in the position of sexual elements, and occurs in monomorphic and dimorphic forms. This polymorphism maximises cross‐pollination and reduces self‐pollination, being very common within the subtribe Cassiinae (Fabaceae). Nevertheless, few studies have investigated the functionality of enantiostyly, particularly in this plant group. The present study aimed to investigate enantiostyly and its functionality in Chamaecrista ramosa, a monomorphic enantiostylous shrub, in an area of coastal vegetation in northeast Brazil. Pollen deposition and capture on the body of floral visitors, the relationship of these data with floral biology and breeding system, and morph ratio were evaluated. Pollen deposition and capture occurred in specific sites of the floral visitor body, showing the functionality of enantiostyly. The floral architecture, associated with the floral visitor behaviour, resulted in indirect pollen deposition on the floral visitor body. This occurred through a loop made by the pollen upon the inner petal surface, similar that generally reported for other Cassiinae. Chamaecrista ramosa is self‐compatible, although no fruit set was observed through spontaneous self‐pollination. The occurrence and number of floral morphs was similar within clumps. Enantiostyly seems to be advantageous for this species, as it results in efficient pollen capture and deposition, reduces the chances of autogamy and maximises intermorph pollen flow.     

Comparative pollen morphology of the Iberian species of Pulicaria (Asteraceae, Inuleae, Inulinae) and its taxonomic significance

To better understand the taxonomy of Pulicaria, the pollen wall architecture of the six Iberian species were investigated using light (LM) and scanning electron microscopy (SEM). The exine structure of Pulicaria odora was also investigated using transmission electron microscopy (TEM). Statistical analysis was performed to distinguish taxonomically significant morphometric information from all the measured parameters of pollen grains. It was found that the exine sculpture characters, with special importance paid to the spines, were the most useful of all characters to define Pulicaria pollen types and separate the species. Three pollen types distinguishable through the spines morphology and the inter-spinular sculpture are described: P. microcephala pollen type (incl. P. microcephala), P. vulgaris pollen type (incl. P. vulgaris), and P. dysenterica pollen type (incl. P. dysenterica, P. odora, P. paludosa and P. sicula). A dichotomous key to these Pulicaria pollen types is proposed. The distribution of P. dysenterica, P. odora, P. paludosa and P. sicula in more than one leaf node in the classification tree reveals that the pollen grains of these species are difficult to segregate. Therefore, the construction of a satisfactory dichotomous key to the P. dysenterica pollen type species is not feasible. Yet, the different spines apex morphology between P. microcephala and P. paludosa and the existence of significant differences in five of the eight studied quantitative pollen characters of these two taxa, supports the opinion that the Berlengas Islands endemic P. microcephala should be accepted as a separate species. In addition, the differences among the spines morphology of P. vulgaris, P. microcephala, and the other four Iberian (and European) species, strengthen the conclusion that the section Pulicaria is non-monophyletic.     

Flower morphology and pollen germination in the genus Capsella (Brassicaceae)

Evolutive changes in mating systems are often accompanied by changes in flower morphology, such as the reduction in size or even loss of petals, changes in production of volatiles, pollen/ovule ratio, the position between anthers and stigma and the germination time of pollen after pollination. These changes have been merged under the term “selfing syndrome” and often result in new taxonomic species. The evolutionary shift frequently happens parallel within many families and genera, for example within the Brassicaceae family. Within the genus Capsella, which is closely related to the molecular model species pair Arabidopsis lyrata (SI)/A. thaliana (SC), we studied self-incompatible and self-compatible species. SC species C. rubella and C. bursa-pastoris produce in comparison with the SI species C. grandiflora (i) smaller petals as the result of decreased cell division and only less of decreasing cell volume, (ii) less production of pollen in one flower, (iii) show a lesser incision between the two valves of the fruits, in combination with a shorter style, and (iv) have a much quicker fertilization of SC pollen after pollination. Crossing success between the diploid species, between different provenances of the tetraploid C. bursa-pastoris, and between the two diploid species and particular individuals of the self-incompatible C. grandiflora has been proven.     

Palynological characters of Glycyrrhiza,Glycyrrhizopsis,and Meristotropis(Leguminosae),with special reference to their taxonomic significance

Li X-Y.1992.Studies on germplasm of Glycyrrhiza by using different taxonomic methods.Advances in Plant Taxonomy in Northwest China 1:7-24.

Li X-Y.1993.A study of the system and new taxa of genus Glycyrrhiza L.Bulletin of Botanical Research 13(1):14-43.

Turrill WB.1937.Glycyrrhizopsis syriaca Turrill.Bulletin of Miscellaneous Information 2:79.

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Taxonomic characters of the staminal tube and epicalyx in Brazilian Pavonia (Malvaceae)

This study was based on the analysis of staminal tube and epicalyx morphology of species ofPavonia (Malvaceae) from northeastern and southeastern Brazil. The importance of characters in the infrageneric taxonomy is discussed. In general, the variability in staminal tube and epicalyx characters are useful mainly in separating closely related species and a few sections; these characters, however, cannot be used to separate subgenera.     

Characterization of microsatellite loci in polyploid Lavatera assurgentiflora ssp. assurgentiflora and ssp. glabra (Malvaceae)

Lavatera assurgentiflora (Malvaceae) is one of four species of the genus Lavatera native to California and Baja California. Two geographically defined subspecies are recognized: L. a. assurgentiflora on the northern islands and L. a. glabra on the southern islands. We isolated nine polymorphic microsatellite loci that amplify in both subspecies of L. assurgentiflora. Substantial levels of polymorphism were observed at many of the loci. Four loci exhibited more than 10 alleles, polymorphism information content ranged from 0.4 to 0.8, and up to six alleles were found in some individuals, supporting reports that these taxa are hexaploid. All loci also amplified in Lavatera lindsayi from Guadalupe Island, and we anticipate that they will cross‐amplify in other California Lavatera species as well.     

Ovulate cone,pollination drop,and pollen capture in Sequoiadendron (Taxodiaceae)

In Sequoiadendron ovules are borne inside the ovulate cone, and pollination drops secreted from these ovules collect pollen. We examined: (1) the relation between ovular position and pollen capture; (2) pollen behavior when in contact with a pollination drop; and (3) ultrastructure of ovules during pollination drop secretion. During wet periods a water sheet forms on the surface of the cone due to bract shape and wettability. Pollination drops persist inside the wetted cone, and pollen capture resumes immediately after drying. Pollen landing on a pollination drop is taken inside the drop and carried into the micropyle when the drop contracts. Several notable ultrastructural features appear in the nucellus, integument, chalaza, and bract lamina during pollination-drop secretion. The abaxial surface of the lamina is covered by a membrane that may contribute to the wettable nature of the surface.     

On a new subsection of Pandanus section Cauliflora (Pandanaceae) with paniculate staminate inflorescence structure,distinctive leaf anatomy and pollen morphology

A new subsection, Pandanus section Cauliflora subsection Paniculiflora, is described to contain P. halleorum, on the grounds of the paniculate structure of its staminate inflorescence, a feature not known elsewhere within the genus Pandanus. Both leaf anatomy and pollen morphology appear to support this taxonomic separation.     

The effect of pollen protein concentration on body size in the sweat bee Lasioglossum zephyrum (Hymenoptera: Apiformes)

Adult bees and wasps provide all the food their offspring require to grow from egg to adult. For a given diet, offspring body size generally increases with an increase in the amount of food consumed as a larva, but the extent to which body size is influenced by the type of food consumed is poorly known. Pollen ranges from 2–60% protein among plant species, and bees are extremely efficient at assimilating nitrogen; therefore, it seems likely that either parent bees adjust the size of larval provisions to compensate for differences in pollen protein concentration or bee offspring attain different body size depending on the pollen type(s) consumed as a larva. We presented the generalist sweat bee Lasioglossum zephyrum with pollen diets that differed in protein content and monitored offspring body size during two experiments. In a protein supplementation experiment, diets ranged from 20–66% protein and consisted of Typha pollen amended with soy protein. On a pollen/soy diet, offspring body size increased 25% with a shift from 20–37% protein, but did not increase further at greater protein concentrations. In a multiple pollen experiment, pollen diets ranged from 20–39% protein and consisted of eight pollens that differed naturally in protein concentration. The largest offspring arose from the most protein-rich pollens, whereas much smaller bees developed on protein-poor pollens. Provision size only predicted offspring size when pollen type, and therefore protein quantity, was considered. Adult foragers did not adjust provision size to compensate for pollen protein. Therefore, offspring body size appears to result from a combination of controlled (provision size) and uncontrolled (pollen quality) factors that arise out of bee foraging decisions.     

Distribution of loosely-bound calcium in the vegetative and generative cells of the pollen grains in Chlorophytum elatum

We used chlorotetracycline fluorescence, alizarin staining and potassium pyroantimonate methods, as well as X-ray microanalysis, to demonstrate the differential localization of Ca2+ during pollen maturation. Level of loosely-bound Ca2+ ions was higher in the generative cell than in the vegetative cell of the mature pollen grain which is one of the symptoms of metabolic differentiation of the two sister cells. This revised version was published online in July 2006 with corrections to the Cover Date.     

Airborne Poaceae pollen in Porto (Portugal) and allergenic profiles of several grass pollen types

This work aims to investigate the presence of airborne grass pollen and to identify antigenic and allergenic profiles from eight different grass species collected in the Porto region (Portugal). Poaceae airborne pollen, sampled using a Hirst-type volumetric trap during 2003–2007, was the second most abundant type, and high concentrations were found from April to August. Pollen proteins extracted from the eight grass species collected were separated by SDS-PAGE, being the allergenic profile investigated by immunoblotting using sera from atopic patients and maize profilin polyclonal antibody (ZmPRO3). Pollen extract profiles showed several bands ranging from 10 to 97 kDa. In immunoblotting studies, a low molecular weight protein (12–13 kDa) was recognized by profilin antibody. Also, in all pollen extracts except Zea mays, the IgE binding proteins of 12–13 kDa were detected in sera from the 25 patients with different sensitization profiles presenting high IgE values (>80 kU/l). This protein can be considered as a potential causal agent of the allergic respiratory diseases.