Pollen Tube Development and Characteristics of the Protein Emission in Conifers

When ripe, viable pollen of Pinus contorta, Pinus nigra, Piceasitchensis, Abies alba and Cedrus deodara is germinated on asuitable artificial substrate, the process of pollen tube growthbegins 12–36 h later, according to the species. The tubeemerges at the leptoma, a structurally specialized site in thepollen wall, and the early tube wall is continuous with thetwo microfibrillar intine strata within the grain. Later inpollen tube development, when cytoplasmic zonation has beenestablished, only the inner of these two wall layers is differentiated. Cytochemical methods show that, during hydration and throughoutthe period of tube growth in culture, proteins are releasedfrom the pollen grains; before germination most conspicuouslyfrom the leptoma, subsequently from the tube itself. The emissioncontains a number of hydrolytic enzymes and a non-catalyticmoiety. Gel-electrofocusing reveals that the hydrolases releasedfrom germinating Pinus contorta pollen include several acidphosphatase and esterase isozymes, and that there are differencesbetween the composition of the emission and the spectrum ofsoluble proteins extracted from the pollen grains before germination.Analysis by immunodiffusion demonstrates that two componentswith antigenic characteristics present in the quiescent pollengrains are represented in the emission. The possible utilityof the released components in the biology of conifer reproductionis discussed. Pinus contorta, Pinus nigra, Picea sitchensis, Abies alba, Cedrus deodara, lodgepole pine, Austrian pine, Sitka spruce, European silver fir, deodar, pollen tube, pollen germination, protein release, isoelectric focusing     

Zur Taxonomie,Verbreitung und Ökologie des Filzigen Schmierlings Chroogomphus helveticus (Sing.) Moser

Chroogomphus helveticus is an european, dealtomontanous species with a south-hercynian-alpian-carpathian and illyrian-macedonian distribution. It grows in association with various conifers. Picea abies, Pinus cembra, Pinus peuce, Pinus strobus and Abies alba probably are partners of the mycorrhiza. The area is similar to that of Abies alba, Hygrophorus marzuolus and various dealpine plants. Distribution centres are districts, where 5-needled pines (Pinus cembra, Pinus peuce) are to be found naturally. Chroogomphus helveticus is to be found in an altitude from 300 to over 2000 m NN. The species is acidophilous, but not strongly bound to acid soils. A subdivion of the species into subspecific taxa is not possible. The closest relative of Chroogomphus helveticus occurs in Asia and Northern America. An other related european species is only known from England.     

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.     

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

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

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

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

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

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

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 dispersal and deposition characteristics of Abies alba, Fagus sylvatica and Pinus sylvestris, Roztocze region (SE Poland)

Pinus sylvestris L., Abies alba Mill. and Fagus sylvatica L.—the significant forest forming tree species in Europe are important for palaeoecological interpretations based on the results of pollen analysis of fossil deposits. The potential pollen loading for Pinus sylvestris, Abies alba and Fagus sylvatica was modelled using simulated and actual vegetation maps, measured fall-speed values and pollen productivity estimates from the literature. The influx of fir pollen drops sharply with distance from the pollen source due to the high fall speed and moderate pollen productivity. The vast majority of Abies alba pollen is deposited within less than 50 m of the sampling site and a major proportion within 100 m. For beech the corresponding numbers would be 300 and 1,800 m, and for pine 1,000 and 4,500 m. The observed mean pollen accumulation rate (PAR) values for Pinus and Fagus were ca. 5,800 and 1,100 grains cm⁻² year⁻¹, respectively. In the case of Abies, the mean annual PAR for the whole region is ca. 700 grains cm⁻² year⁻¹. In SE Poland the regional signal is represented by PARs of Abies alba <200 grains cm⁻² year⁻¹ and of Fagus sylvatica <500 grains cm⁻² year⁻¹. The local presence/absence threshold values for Abies alba, Fagus sylvatica and Pinus sylvestris are >1,000 grains cm⁻² year⁻¹, >2,000 grains cm⁻² year⁻¹ and >3,500 grains cm⁻² year⁻¹ respectively.     

Pollen diversity and its implications to the systematics of Poecilanthe (Fabaceae,Papilionoideae, Brongniartieae)

The small South-American genus Poecilanthe has a striking morphological diversity in leaf type, inflorescence, seed morphology and chemical composition. Recent phylogenetic work also shows that Poecilanthe is paraphyletic. Despite the importance of palynology to better understand morphological diversity and potentially inform evolutionary analyses, the pollen morphology of Poecilanthe and most of its close relatives is unknown. This study uses light and electronic microscopy to describe the pollen morphology of eight species of Poecilanthe and the four related genera Ormosia, Harpalyce, Clathrotropis and Cyclolobium. We found pollen grains colpate only in four species of Poecilanthe and Harpalyce brasiliana and colporate pollen grains in the other four Poecilanthe species and the other related genera (Ormosia, Clathrotropis and Cyclolobium). An identification key for pollen of all species is provided. Using principal component analyses (PCA) we found that pollen grains of the Poecilanthe have considerable diversity. However, only limited correspondence between the PCA clusters and the Poecilanthe clades was found, suggesting that pollinic characters do not reflect evolutionary history in this group.     

Regeneration potential of conifers along an elevation gradient under highly disturbed regimes in the western Himalayan region

This paper focuses on growth pattern of seedlings from tree-ring proxies and their performance at different altitudes under high disturbance regime. The disturbance is predominately anthropogenic. Four conifer species found during investigations, namely, Pinus wallichiana, Pinus roxburghii, Cedrus deodara and Abies pindrow. The parameters chosen for assessment of regeneration potential were age and growth rate. In addition, edaphic and topographic characteristics of thirty disturbed forest stands were also determined. The stands were deterministically selected because these were deteriorating with respect to tree population, biodiversity and degradation of soil. Seedling density varied in the order: P. wallichiana > Pinus roxburghii > C. deodara > Abies pindrow while the growth rate was exhibited in the order Pinus roxburghii > P. wallichiana > Abies pindrow > C. deodara. These findings suggest that Pinus roxburghii is the most suitable species (sub tropical species) at lower elevations (~1600–1900 a.s.l.) with regard to its regenerative ability and consequently potentially useful for the conservation of these forests. P. wallichiana showed highly significant (P < 0.01) correlations with PC1 (primarily controlled by total dissolved salts and water holding capacity) only whereas Abies pindrow was highly correlated (P < 0.001 and P < 0.01) with PC1 and PC2 respectively (function of oxidative-reductive potential and water holding capacity) while C. deodara and Pinus roxburghii did not show correlation with any of the PCA components. In the light of current findings, Pinus roxburghii was found to be effectively adapted to the environment of the study area. Growth rate of species steadily decreased in response to unfavorable conditions. The other pine species i.e. P. wallichiana (moist temperate species) also showed some degree of adaptability under the influence of predefined environmental attributes. Hence pines are most likely the species that can be able to retain forest cover in future and are the best choice for restoration of these forests. However, the other conifers i.e. C. deodara and Abies pindrow are also able to withstand the physiographic characteristics and the extent of perturbation and persisting possibly beyond their tolerance limits but they need to be preserved and retained in these forests. Conifers are still giving positive response with respect to growth rate and their adaptive compatibility to such an extent that this forest can recover if management and conservation strategies are implemented. Therefore, it is strongly recommended that seedlings and saplings should be conserved to assure future forest cover.     

Fuel treatment effects on soil chemistry and foliar physiology of three coniferous species at the Teakettle Experimental Forest, California, USA

A full factorial design crossing overstory (O) and understory (U) thinning and prescribed burning (B) was started at Teakettle Experimental Forest, California, in 2001 with the aim of achieving shifts in species composition to favor fire-resistant pines over fir. The goal of the present study was to evaluate the use of metabolic changes as early indicators for predicting the effects of these treatments on species-specific growth and long-term productivity of Pinus jeffreyi, Pinus lambertiana, and Abies concolor. Foliar polyamines, amino acids, soluble proteins and chlorophyll were quantified and related with foliar and soil chemistry. Most changes in soil chemistry occurred only with combined treatments (BU or BO). Changes in foliar metabolism were not driven by soil chemistry. In general, the pines were more sensitive to water stress as compared to fir as indicated by proline content. Understory thinning had no effect on any species. Both O and BO had species-specific effects on foliar amino acids, chlorophyll, soluble proteins, and inorganic ions. In addition, both O and BO were the most extreme thinning treatments for pines as they greatly increase the time needed to replenish carbon stocks. With the exception of some amino acids, B by itself had no major effects on foliar inorganic ions, chlorophyll content, and polyamines for any of the three species while BU caused a decrease in chlorophyll in white fir, suggesting a decline in photosynthetic capacity. These data point to BU as the best management option to specifically decrease the growth of fire-sensitive white fir without a major impact on pines.     

Fossil records of subsection Pinus (genus Pinus,Pinaceae) from the Cenozoic in Japan

Extant pines of subsection Pinus (section Pinus, genus Pinus, Pinaceae) are predominantly distributed in Eastern Asia. However, the extent of diversification in the section has yet to be fully clarified. We reviewed fossil records of subsection Pinus from Japan and collected permineralized materials, in which anatomical details are preserved for better understanding of the diversification. Our results suggest that this subsection appeared in Japan no earlier than the Middle Eocene, with extant species (i.e., Pinus densiflora and Pinus thunbergii) appearing around the beginning of the Pleistocene. Pinus fujiii (Early Miocene to Early Pleistocene) is inferred to have a close affinity to P. thunbergii based on the medial arrangement of its leaf resin canals. Additionally, P. fujiii has a similar cone morphology to those of extant species living in China, bridging the morphological gap between P. thunbergii and Chinese relatives of P. thunbergii as inferred by molecular phylogenetic analyses. Our results also suggest that taxonomic revisions of Pinus miocenica and Pinus oligolepis are required among the Japanese fossil species reported to date.     

Pollen morphology and taxonomy of the subtribe Diocleinae (Leguminosae: Papilionoideae: Phaseoleae)

The pollen morphology of the thirteen genera currently included in the subtribe Diocleinae is described. Nine pollen types with a number of subtypes are recognized. These are arranged into two main groups. The first comprises the macromorphologically anomalous genera Calopogonium, Herpyza and Pachyrhizus which, although united by some pollen characters, are distinct both from each other and from the rest of the subtribe. The second group, consisting of the remaining genera which can to some extent be distinguished from each other by their pollen morphology, nevertheless appear to make up both macromorphologically and palynologically a more natural Diocleinae. The six pollen types in the second group are further divided into two slightly overlapping subgroups. Luzonia and Macropsychanthus are palynologically somewhat distinct but, together with Dioclea and Canavalia, have generally rather large, oblate pollen grains with a complete or perforate tectum, in contrast with the pollen of the genera Camptosema, Collaea, Cratylia and much of Galactia which is smaller, spheroidal with a reticulate tectum.Dioclea has some species with isopolar pollen and others with heteropolar pollen grains and this more or less correlates with subgeneric divisions within the genus. Galactia from the Caribbean area has similar but much smaller pollen. The taxonomic significance of this parallel between the pollen morphology of Dioclea and Caribbean Galactia is unclear. The pollen of Canavalia appears to show no significant variation.A possible correlation between the pollen subgroups with ecological habitat and pollinators is discussed.     

Genetic relationships among Mexican white pines (Pinus, Pinaceae) based on RAPD markers

Genetic relationships among Mexican white pines have not been completely resolved by DNA sequencing analyses. The use of random amplified polymorphic DNA (RAPD) markers for the study of interspecific relationships has been questioned because of the possible lack of homology of co-migrating bands between species. However, several RAPD based studies on pines have provided sufficient information to discriminate between closely related taxa. Genetic relationships among four species of Mexican white pines (Pinus ayacahuite, Pinus strobiformis, Pinus lambertiana and Pinus chiapensis) were estimated based on RAPD markers. Sixty-nine primers generated 247 bands in pooled DNA samples from ten populations. In addition, four selected primers generated 27 bands in 176 individual DNA samples. Unweighted Pair Group Method with Arithmetic Average (UPGMA) dendrograms based on Jaccard similarity indices were constructed. The results suggest that the closest pine species analyzed were P. ayacahuite and P. strobiformis, followed by P. lambertiana. The most genetically distant species was P. chiapensis. Cluster analyses did not support P. strobiformis as a distinct species from P. ayacahuite.     

Phylogeography of Pinus armandii and Its Relatives: Heterogeneous Contributions of Geography and Climate Changes to the Genetic Differentiation and Diversification of Chinese White Pines

Geographic barriers and Quaternary climate changes are two major forces driving the evolution, speciation, and genetic structuring of extant organisms. In this study, we used Pinus armandii and eleven other Asian white pines (subsection Strobus, subgenus Pinus) to explore the influences of geographic factors and Pleistocene climatic oscillations on species in South China, a region known to be centers of plant endemism and biodiversity hotspots. Range-wide patterns of genetic variation were investigated using chloroplast and mitochondrial DNA markers, with extensive sampling throughout the entire range of P. armandii. Both cpDNA and mtDNA revealed that P. armandii exhibits high levels of genetic diversity and significant population differentiation. Three geographically distinct subdivisions corresponding to the Qinling-Daba Mountains (QDM), Himalaya-Hengduan Mountains (HHM) and Yungui Plateau (YGP) were revealed in mainland China by cpDNA. Their break zone was located in the southeastern margin of the Qinghai-Tibetan Plateau (QTP). A series of massive mountains, induced by the QTP uplift, imposed significant geographic barriers to genetic exchange. The disjunct distribution patterns of ancestral haplotypes suggest that a large continuous population of the white pines may have existed from southwest to subtropical China. Repeated range shifts in response to the Pleistocene glaciations led to the isolation and diversification of the subtropical species. The two Taiwanese white pines share a common ancestor with the species in mainland China and obtain their chloroplasts via long-distance pollen dispersal from North Asian pines. Distinct genetic patterns were detected in populations from the Qinling-Daba Mountains, Yungui Plateau, Himalaya-Hengduan Mountains, and subtropical China, indicating significant contributions of geographic factors to the genetic differentiation in white pines. Our study depicts a clear picture of the evolutionary history of Chinese white pines and highlights the heterogeneous contributions of geography and Pleistocene climatic fluctuations to the extremely high plant species diversity and endemism in South China.     

凤仙花属（Impatiens L.）10种植物花粉形态的扫描电镜观察

利用扫描电镜观察了10种凤仙花属（Impatiens L.）植物的花粉形态。结果表明：本属花粉为单粒花粉,呈长圆形至长矩圆形,大小为20.3～46.7 μm,具角萌发孔,网状纹饰,网眼明显;根据花粉网状纹饰中网眼内是否具颗粒状突起可将其分为2类：（1）网眼内无或近无颗粒状突起,黄金凤（I. siculifer）和婺源凤仙花（I. wuyuanensis）的花粉纹饰属于这一类型;（2）网眼内有明显颗粒状突起,其余8个种的花粉纹饰均属于该类型。研究表明,花粉特征,特别是花粉粒网状纹饰中网眼内有无颗粒状突起及颗粒状突起的形态等特征,在凤仙花属内常具种水平上的可见变异,因而可作为种类划分的依据,它们在分类学上的价值应予以关注。     

Morphology and variability of pollen of the genus <Emphasis Type="Italic">Spiraea</Emphasis> L. (Rosaceae) in Siberia and the Far East

Pollen of 12 species of the genus Spirea L. growing in different regions of Siberia and the Far East was investigated. The ultrasculpture of pollen grains is described. On the basis of aperture morphology and exine sculpture, pollen grains are typified, with key indices given for their identification. The species of the Spiraria section are distinguished by large grains. Pollen grains of S. media and S. alpina considerably vary in size. The level of natural polymorphism of palynological indices has been established.     

Pollen morphology of selected crop plants from southern China and testing pollen morphological data in an archaeobotanical study

Identification of pollen grains of cultivated plants is essential in archaeobotanical studies. In this study, we investigated the pollen morphology of 30 species which are representatives of most of the crop plants in southern China, using a light microscope. Our results show that the pollen grains of these species or genera can generally be identified by their size, aperture(s) and exine sculpture. We found that: (1) some cultivated cereals can be distinguished from wild species of Poaceae according to their size frequency combined with their morphological features; (2) the lengths of the equatorial diameter (E), polar axis (P) and the greatest dimension of the lumina (the size of the network sculpturing) of the exine reticulum may be diagnostic features to distinguish some brassicaceous vegetables. There are significant differences between the E and P values among Brassica campestris (B. rapa, oilseed rape, Chinese cabbage), B. alboglabra (B. oleracea var. alboglabra, gai lan, Chinese kale), B. parachinensis (B. rapa var. parachinensis, choy sum, Chinese flowering cabbage) and B. chinensis (B. rapa ssp. chinensis, pak choi), but moderate differences in the longer axis length of the reticulum lumina, which provide potential for identifying species on the basis of pollen grains. We compared the P values and the longer axis length of the lumina of modern specimens of Brassicaceae pollen grains with those of fossil pollen extracted from the Ming-Qing cultural layer in the Fuqikou site at Chongqing, China, and found that the fossil pollen grains of Brassicaceae probably represent vegetable plants related to B. parachinensis. Moreover, we measured the diameters of rice pollen grains from modern paddy fields to assess the pollen size frequency and found that the size range from ~?34 to 38 µm is closely associated with rice pollen in southern China, which can be used to detect pollen signals of human activities in archaeobotanical investigations.     

Variation of pollen morphology, and its implications in the phylogeny of Clematis (Ranunculaceae)

Clematis s.l. (including Archiclematis and Naravelia) is a genus of approximately 300 species with cosmopolitan distribution. The diversity of its pollen was surveyed in 162 taxa belonging to all infrageneric groups of Clematis s.l. Pollen morphology was investigated by use of scanning electron microscopy to identify useful characters, test taxonomic and systematic hypotheses, and elucidate pollen character evolution on the basis of the molecular phylogeny. Clematis pollen is small to medium (14.8–32.1?μm?×?14.2–28.7?μm), oblate to prolate (P/E?=?0.9–1.4) in shape. The apertures may be tricolpate and pantoporate sometimes with 4-zonocolpate and pantocolpate pollen grains as transitional forms. The tricolpate pollen grains are predominant and occur in all the sections of the genus, whereas pantoporate pollen grains can be found in sect. Tubulosae, sect. Viorna, sect. Viticella, and Naravelia only. Phylogenetic mapping of aperture types reveals that the pantoporate pollen type may be the apomorphy in the genus and evolved several times. The surface ornamentation in all taxa studied is similar and characterized by microechinae evenly distributed on the microperforate tectum. The size and density of spinules on the tectum vary greatly but successive in the whole genus. According to the character syndromes of the ornamentation, separating sect. Brachiata from sect. Meclatis is supported. Though pollen morphology may contribute to investigation of problematic taxa, the taxonomic value of pollen morphology is limited at the species level.     

Pliocene white pine (Pinus subgenus Strobus) needles from western Yunnan,southwestern China

Abstract

The fossil records of Pinus L. are abundant since the Late Cretaceous, especially for the subgenus Pinus L. (the hard pines). However, those of the subgenus Strobus (D. Don) Lemmon (the white or soft pines) are not well documented. In this study, we describe a new species of white pines, Pinus plioarmandii sp. nov., from the Pliocene of western Yunnan, southwestern China. This species mostly resembles extant P. armandii Franch. in gross morphology and cuticular structure of needles. Molecular dating showed that the Asian white pines split into two lineages around the Late Miocene, and the Pinus armandii clade diverged at the Early Pliocene. The present fossil occurrence indicates that Pinus armandii might originate in southwest China and probably in the western Yunnan. The glacial events during the Pleistocene might be the major factors for the retreat of the white pines from western Yunnan, and the rapid uplift of the Yunnan Plateau and deep incision of the river valleys since the Pliocene had posed a significant geographic barrier for their reconnection in the subsequent warm climate condition.     

Systematic importance of pollen morphological features of selected species from the genus Rosa (Rosaceae)

The aim of this study is verification of the taxonomic usefulness of the pollen grain features studied, based on pollen morphology of 32 wild species from all 4 subgenera and all 10 sections of the genus Rosa, mainly for delimitation of subgenera, sections, and species. The measurements and observations were carried out with both light microscopy and scanning electron microscopy. Only correctly formed pollen grains (30 per specimen) were measured, and 960 pollen grains were examined in total. They were analyzed for 14 quantitative features of pollen grains and exine sculpturing and the following qualitative ones: outline, shape, and operculum structure. Our study revealed that the diagnostic features of pollen grains studied were: exine sculpture, length of polar axis, and pollen shape (P/E ratio). On the basis of the above characters, five species were isolated and the remaining ones were included in several groups isolated on the basis of exine sculpture types. The following three exine sculpture types occurred in the species studied: granular-verrucate (in R.?stellata), striate-psilate (in R.?multibracteata and R.?multiflora), and striate (the remaining species). R.?banksiae is characterized by small pollen grains, while R.?setigera has strongly elongated pollen with P/E ratio >1.5. Exine sculpture features considered to be diagnostic should be treated as auxiliary because they fail to differentiate individual species, although they can be helpful in distinguishing groups of species of similar exine sculpture. The arrangement of the species examined on a dendrogram only slightly corroborates division of the Rosa genus into subgenera and sections currently adopted in taxonomy (Rehder 1940). An interesting result was reported for the species studied from the Caninae (R.?agrestis, R.?canina, R.?dumalis, R.?jundzillii, and R.?rubiginosa) section which, despite hybrid nature, with the exception of R.?villosa, grouped in the same, most separated group of species.     

Taxonomic significance of pollen morphology for species delimitation in <Emphasis Type="Italic">Psidium</Emphasis> (Myrtaceae)

Previous studies reported Psidium as one of the most difficult genera to delimit within the American Myrtaceae. Even though palynology has improved the taxonomy of Angiosperms, information about the usefulness of pollen morphology for taxonomic purposes in Myrtaceae remains contradictory. Here, we investigate the significance of pollen morphology for Psidium taxonomy with specific focus on its usefulness for determining species groups of taxonomic significance. Pollen traits observed by light and scanning electron microscopy were quantified and examined using cluster and ordination analyses. Average size of pollen grains was visualized by boxplots. Pollen grains of Psidium are isopolar, oblate, peroblate or oblate-spheroidal, 3-syncolporate or 4-syncolporate. The sexine ornamentation is rugulate, granulate or spinulose-granulate and differs between the mesocolpium and apocolpium. Cluster analysis revealed four distinct groups: Psidium cauliflorum (G1) and Psidium oligospermum (G3) as single-species groups; Psidium brownianum, P. oblongatum, P. ovale, P. sartorianum, P. guajava, Psidium sp. 1, Psidium sp. 2 (G2), and Psidium cattleianum, P. longipetiolatum, P. guineense, P. myrtoides (G4). Supported by ordination analysis, three traits better explained these groups: type of exine ornamentation, size of P-EV and pollen shape. The used approach efficiently distinguished related species, as well as explained species groups of taxonomic significance suggesting pollen morphology to be a significant source of information for taxonomic studies in Psidium.