Pollen morphology of Brazilian Fevillea (Cucurbitaceae)

Pollen morphology of the five Brazilian species of the genus Fevillea (F. bahiensis, F. cordifolia, F. passiflora, F. pedatifolia, and F. trilobata) was studied using light and scanning electron microscopy. Pollen in these species is generally stenopalynous, which is in agreement with observations in previous studies of other species. Pollen is shed in monads and characterised by being isopolar, radially symmetric, prolate, and striate. Pollen is of medium size, tricolporate, with long and narrow colpi, a circular endoaperture and a reduced polar area. The exine is up to 2 μm thick.     

Effects of X-rays and Colchicine on Pollen of Trichosanthes anguina L. (Cucurbitaceae)

Pollen grains of M, and C, generation plants of Trichosanthes anguina L. were studied after treatment of seeds with X-rays and colchicine respectively. Pollen sterility increased with increase in X-ray dose and colchicine concentration. The polar axis of X-irradiated populations was shorter than that of controls. But colchicine treatment resulted in larger pollen grains than the controls, although the exine did not increase as much. Ex-perimentally-produced tetraploids had larger pollen grains than diploids and triploids. The triploids were characterised by changes in pore morphology. Of 293 treated plants examined, 11 aberrant plants were isolated in the M, and C, generations. These plants had large and small fertile pollen grains, and also showed treatment effects in external morphology and chromosomal aberration during meiosis. The changes in polar diameter were not associated with variation in chromosomal material.     

Pollen morphology of Zehneria s.l. (Cucurbitaceae)

A growing body of experimental data obtained from sporoderm ontogenetic studies led to the appearance of the ‘micellar’ hypothesis. The hypothesis is that the sequence of sporoderm developmental events represents the sequence of self-assembling micellar mesophases, initiated by genomically given physico-chemical parameters, which are then picked up by physico-chemical self-assembly. However, besides morphological evidence, the best proof of this hypothesis would be an experimental modelling of sporoderm-like patterns. The main idea of this study is to remove the influence of the genome, selecting substances and their concentrations for simulations to replace it, and then to trace what ‘pure’ self-assembly is capable of constructing. Our aim in this study was to simulate mainly young structures in sporoderm development, i.e. the glycocalyx and the primexine. Several polysaccharide gels (as a callose substitute) and surfactants (as glycocalyx and sporopollenin monomer substitutes) were mixed at different concentrations and combinations, thermally set and left to condense. A number of patterns were obtained in colloidal solutions in the course of condensation, simulating structures at different stages of exine development. Their structures were observed and analysed with transmission electron microscopy (TEM). Our first experiments on the modelling of biological patterns in vitro have shown encouraging results.     

Pollen competition in a natural population of Cucurbita foetidissima (Cucurbitaceae)

The pollen competition hypothesis predicts that when the number of pollen grains deposited onto stigmas exceeds the number of ovules, selection can operate in the time frame between deposition and fertilization. Moreover, because of the overlap in gene expression between the two phases of the life cycle, selection on microgametophytes may alter the resulting sporophytic generation. The extent to which pollen competition occurs in nature has been unclear, because tests of the predictions of the pollen competition hypothesis have used cultivars and/or artificial growth conditions and hand-pollination techniques. In this study we used a wild species, Cucurbita foetidissima, in its natural habitat (southern New Mexico) to determine the amount and timing of the arrival of pollen onto stigmas, the relationship between pollen deposition and seed number, and the effects of the intensity of pollen competition on progeny vigor. We found that ～900 pollen grains are necessary for full seed set and that a single visit by a pollinator results in the deposition of 653.0 ± 101.8 pollen grains. About 29% of the flowers receiving a single pollinator visit had 900 or more pollen grains on its stigma. Moreover, within 2 h of anthesis, >4000 pollen grains were deposited onto a typical stigma, indicating that multiple pollinator visits must have occurred. Fruits produced by multiple visits had greater seed numbers (206 vs. 147) than fruits produced by a single visit. Finally, the progeny produced by multiple pollinator visits were more vigorous than those produced by single visits with respect to five measures of vegetative growth (MANCOVA, Wilks' lambda = 0.96, F(6,370) = 2.54, P < 0.02. These data demonstrate that conditions for pollen competition exist in nature and support the prediction that pollen competition enhances offspring vigor.     

Pollen morphology of Alstonia (Apocynaceae)

The pollen of Alstonia has been studied by light and scanning electron microscopy. The pollen grains are always colporate. Four distinct pollen types could be recognized. Type 1 (2‐aperturate) and type 2 (3‐aperturate) have rounded endopores, while type 3 (?<36 μm) and type 4 (?>49 μm) possess H‐endoapertures. Probably, all four types have harmomegathically inactive apertures and folding mesocolpia. Type 1 is found in five species of section Alstonia. The other species of this section and the monotypic section Winchia have type 2. The sections Dissuraspermum, Monuraspermum and Tonduzia have pollen type 3. This type may be subdivided on the basis of some minor (overlapping) features, which more or less segregate Dissuraspermum from Monuraspermum. Palynologically, the monotypic American section Tonduzia appears to be most related to the Malesian/Australian/Pacific sections Monuraspermum and Dissuraspermum, and not to the African species of section Alstonia.     

Pollen morphology of JapaneseSymplocos (Symplocaceae)

The pollen morphology of all 23 Japanese species ofSymplocos (1 of subgenusEusymplocos, and 22 of subgenusHopea) was comprehensively studied using LM, SEM and TEM, and found to be classifiable into two types (Type I and II) primarily on the basis of wall structure. Type I, characterized by a thick tectum lacking a supratectal structure and reduced columellae, occurs in subgenusEusymplocos, while Type II, characterized by a thin tectum with a supratectal structure and generally distinct columellae, occurs in subgenusHopea. Resemblances in wall structure suggest a closer relationship of subgenusEusymplocos to subgenusMicrosymplocos as well as of subgenusHopea to subgenusEpigenia. This fact contradicts the earlier proposed infrageneric classification, and may require its revision. Within Type II, five subtypes are recognized primarily on the basis of sculpture combined with other pollen characters. Systematic value of sculpture (i.e., subtype), aperture morphology and “globules”, as well as certain species relationships based on those characters, are also discussed.     

Pollen morphology of Gontortae (Acanthaceae)

Variation in pollen morphology is described and illustrated for 36 genera of Acanthaceae with contorted corolla aestivation. A parsimony analysis of pollen characters is presented.     

Pollen morphology of Broussonetia (Moraceae)

The pollen of seven species of Broussonetia (including Section Allaeanthus) and one species of Malasia were examined with light, scanning and transmission electron microscopy. The pollen of all species is diporate with slightly annulate pores, and scabrate exine sculpturing. The pollen is small and all species have a columellate wall structure. The closely related genus Malasia is similar to Broussonetia. The similarity of the pollen in Section Broussonetia and Section Allaeanthus suggests that Allaeanthus be retained in the genus Broussonetia.     

Pollen grain morphology ofCoris (Primulaceae)

Pollen grain morphology, sculpturing, and wall ultrastructure are investigated in two species ofCoris (Primulaceae),C. monspeliensis L. andC. hispanica Lange. The study includes both acetolysed and unacetolysed pollen. No evidence of any major palynological difference is recorded between these two species, apart from a somewhat larger pollen inC. monspeliensis. However,Coris can be distinguished from the remaining members of thePrimulaceae by the conjunction of relatively large pollen grains, prominent margo, and particular tectal pattern causing a reticulate surface with minute luminal perforations decreasing towards the colpi. From both these distinctive features, and others typically primulaceous, some evolutionary considerations are inferred. Finally, the higher proportion of irregular grains inC. hispanica is interpreted in light of environmental stress.     

Pollen morphology in thePortulacaceae (Centrospermae)

Pollen of 110 species from 18 genera in thePortulacaceae has been examined by light and scanning electron microscopy, and a representative number by transmission electron microscopy. Three basic pollen types were found: 3-colpate with thick tectum and foot layer with prominent unbranched columellae and an extremely thin endexine; pantoporate with thick tectum and foot layer with branched columellae enclosing pores and an endexine that is one to two layers thick; pantocolpate with thin tectum and foot layer with broad, short unbranched columellae and an inconspicuous endexine. All pollen types, however, have a spinulose and tubuliferous/punctate ektexine. Also, all the genera except three,Calandrinia H.B.K.,Montia L. andTalinum Adanson are stenopalynous. There is, however, no absolute correlation between pollen morphology and geographical distribution, although both the major centre of palynological diversity and the majority of all species with tricolpate grains occur in South America.     

Pollen morphology ofVigna angularis (Leguminosae)

Pollen grains ofVigna angularis and its var.nipponensis are described with special reference to fine structure of the infratectum of the exine. They are 3-porate-operculate with granular infratectum and thin foot-layer. These features agree with those characterizing the genusVigna. In this species var.angularios and var.nipponensis are quite similar in pollen morphology. This supports the view that the two are closely related.     

Pollen morphology of the Chloridoideae (Gramineae)

Pollen grains of 57 species (representing 42 genera) of the Chloridoideae have been investigated using light, scanning and transmission electron microscopy. Two aperture patterns and nine exine patterns are distinguished using SEM and TEM. These are categorized into five pollen types. Two pollen types are previously not recorded in Gramineae. A key for the identification of these pollen types is presented. Generally, pollen characters have limited systematic value in recognizing taxa at generic level or above in the Chloridoideae. An evolutionary trend is proposed that awaits verification by further systematic study. Pollen characters can be used as indicators for the areas of origin and distribution of the Chloridoideae.     

Pollen morphology of andruris japonica (triuridaceae)

Pollen morphology of Andruris japonica (Triuridaceae) was investigated by light and electron microscopy. The pollen is monosulcate and has a size of 22–25 μm × 25–28 μm in polar view. In the non-apertural region the exine has gemmate to nearly verrucate protrusions of 0.4–0.5 μm in diameter and 0.3–0.5 μm in height, and a foot layer of 0.4–0.5 μm in thickness. The sporoderm of the apertural region has large gemmae of 0.7–0.8 μm in diameter and 0.6–0.7 μm in height, with a thin foot layer of 0.1 μm thickness.     

Pollen morphology of the Gardenieae-Gardeniinae (Rubiaceae)

Pollen grains of 107 species of 61 genera of the Gardeniinae were investigated by scanning electron and light microscopy. The subtribe is europalynous and grains occur either as monads, tetrads or massulae. Grains are porate, colporate or rarely pororate. The majority of the genera has 3-zonoaperturate pollen grains. However, deviating numbers of apertures occur in Byrsophyllum (4–8) and Pseudomantalania (4–5). Pantoporate pollen occurs in Randia . The average equatorial size (E) of monads varies between 13 μm in Anomanthodiu to 59 μm in Posoqueria . The tetrads vary from 37 μm in Casasia to 61 μm in Calochone and Euclinia . The exine is usually reticulate, but also foveolate, rugulate, perforate and psilate exine occurs in the subtribe. The thickness of the exine is only 0.3 μm in tetrad grains of Randia armata and in the pantoporate monad grains of R. ruiziana , whereas the thickest exine occurs in Posoqueria (2.8 pm) and Euclinia (2.9 μm). Tectal excrescenses are generally absent. However, three genera with pollen in tetrads, namely Euclinia, Gardenia and Oligoco-don , show this feature. Contrary to the subtribe most genera are fairly stenopalynous, but in the neotropical genera Alibertia and Randia several different types of pollen are encountered.     

Pollen morphology of the genus Paliurus (Rhamnaceae)

The pollen morphology of the genus Paliurus and the 5 species it comprises is described. Consistent with the general morphological pattern of the family Rhamnaceae, the pollen grains of Paliurus are uniformly isopolar, radially symmetrical, 3-(zono)-colporate and angulaperturate. Despite this general infrageneric uniformity, certain differences and trends can be recognized with respect to pollen size, shape, and tectum architecture.     

Pollen morphology and structure of Zingiber (Zingiberaceae)

The aim of the present study is to describe the morphology and internal wall structure of Zingiber pollen. The pollen of 18 species of Zingiber was examined by light, scanning and transmission electron microscopy. In the sections Zingiber and Dymczewiczia (Horan.) Benth. the pollen grains are spherical with cerebroid sculpturing while in the section Cryptanthium Horan. the pollen is ellipsoid with spira-striate sculpturing. All species have a thin coherent exine and an intine consisting of a thick, radially channeled outer layer and a thin, finely granular inner layer. On the basis of pollen morphology it is proposed that the section Dymczeniczia is included in the section Zingiber. The structure of the pollen wall in Zingiber resembles that of Canna and Strelitzia in having a pollen wall offering an infinite number of germination sites.     

Pollen morphology and systematics of Atripliceae (Chenopodiaceae)

Pollen morphology of 58 species from 17 putative genera of the tribe Atripliceae (Chenopodiaceae) was investigated using light (LM) and scanning electron microscopy (SEM). Morphological variation was analyzed based on a dense sampling of the subtribes Atriplicinae and Eurotiinae, including many of the species in the two largest genera: Atriplex and Obione. The pantoporate pollen grains of Atripliceae are characterized by their spheroidal or subspheroidal shape, flat or moderately vaulted mesoporia with 21–120 pores, tectum with 1–8 spinules and 5–28(?38) puncta per?µm², and 1–13 ectexinous bodies bearing 1–7 spinules each. Taxonomic relevance of the most important pollen morphological characters is discussed (pollen diameter, pore number, pore diameter, interporal distance, spinule and puncta density and ratio, number of ectexinous bodies, and their spinules). Pollen morphological data support the exclusion of Suckleya from the tribe and the recognition of subtribe Eurotiinae, but suggest that it needs to be reviewed. Pollen does not support generic recognition of Atriplex, Neopreissia and Obione and infrageneric subdivisions as currently recognized, and suggests the need to review them. Smaller or monotypic genera, such as Axyris, Ceratocarpus, Endolepis, Krascheninnikovia, Microgynoecium, Proatriplex and Spinacia have distinctive pollen morphological characters that support their generic status. Grayia needs to be reevaluated; although its two species are distinct from all the other species in the study, there are notable differences between each of them, and this suggests they may not form a natural group. Multivariate techniques were employed to investigate if there are discrete patterns of variation within Atripliceae. Principal Component Analyses (PCA) weakly differentiates four groups based on variation in pore number, puncta density per?µm², and ratio between spinule and puncta density per?µm²; species of Ceratocarpus, Haloxanthium, Krascheninnikovia, Manochlamys, Microgynoecium, Spinacia, and some species of Atriplex and Obione are isolated. Preliminary results indicate that pollen data are potentially useful in the classification of the tribe, and further studies will be of taxonomic value.     

Pollen morphology of the subfamily Aurantioideae (Rutaceae)

The Aurantioideae is one of seven subfamilies of the Rutaceae consisting of two tribes, the Clauseneae, containing five genera, and the Citreae, with 28 genera. Each tribe contains three subtribes. The pollen morphology of the subfamily Aurantioideae is described and illustrated for the first time based on light and scanning electron microscopy. Five pollen types have been recognised in the subfamily, based mainly on aperture number and exine ornamentation. The pollen grains show a high degree of intergeneric variation. Pollen grains of Clauseneae are 3-colporate, microstriate or microstriato-reticulate, whereas pollen grains of Citreae are almost always 4/5 colporate with exines varying from microperforate to coarsely reticulate. Congruence between pollen types and the currently accepted classification is discussed, as well as the systematic implications of pollen morphology for the subfamily.