POLLEN MORPHOLOGY OF LYCIUM (SOLANACEAE) SPECIES IN IRAN

Lycium (Solanaceae) has more than 100 species in arid and semi-arid parts of the world. In Iran, this medicinal plant is represented by 6 species, on which no palynological study has been conducted. Pollen morphology of 7 taxa are considered for the first time to evaluate the species relationships based on palynological data. Observations were made by use of Scanning electron microscopy on untreated pollen grains. Multivariate statistical analyses were carried out for qualitative and quantitative pollen features in the species studied. Results show that all pollen grains were monad, isopolar, zonotricolporate in prolate and preprolate shape. Exine sculpture was of striate and regulate patterns. Variations in pollen grains are considered to overcome the identification problems in species separation in morphologically similar taxa in this genus in Iran. The importance of pollen features in delimitation in some genera of Solanaceae was previously proven and the present study elucidates that some features as exine sculpture and some quantitative characters are of diagnostic importance in Lycium species native to Iran.

Pollen morphology of Ellisiophyllum and Sibthorpia (Plantaginaceae, tribe Sibthorpieae) and phylogenetics of the tribe

Pollen morphology of six species belonging to genera Ellisiophyllum and Sibthorpia (Plantaginaceae tribe Sibthorpieae) was studied using light and scanning electron microscopy. The data were analyzed in the light of the first phylogenetic analysis including all but one species of the tribe using DNA sequence data from nuclear ribosomal (ITS) and plastid trnL-F region. Pollen grains in representatives of this tribe are 3-colpate, occasionally 3-porate, suboblate to prolate; mainly medium-sized, rarely small. One major pollen type (3-colpate) is recognized in the tribe. Within this pollen type, six subtypes are distinguished based on their exine sculpture, pollen grain size, length of the apertures, and exine thickness. The obtained results confirm that pollen characters are useful for species identification. Palynomorphological data are consistent with the results of the molecular phylogenetic analyses. All studies support a sister relationship of the widespread European Sibthorpia europaea with the widespread South American Sibthorpia repens and a sister relationship of two insular species, the Balearic Sibthorpia africana and the Madeiran Sibthorpia peregrina. Pollen grains in the tribe Sibthorpieae have both reticulate exine sculpture characteristic for representatives of the Russelieae–Cheloneae–Antirrhineae clades of Plantaginaceae, and also nanoechinate sculpture, which is typical for the Veroniceae and Plantagineae clades of that family. Also, in Sibthorpia repens, we observe a possible transition from the colpate type to the porate type typical for taxa of Plantago and Littorella.

Taxonomic significance of palynomorphological characteristics of selected Centranthus (Caprifoliaceae) species

Pollen morphology of herbarium specimens of four Centranthus species (C. ruber, C. longiflorus, C. kellereri and C. calcitrapae) was studied using LM and SEM. The research aim was to provide data on their pollen characteristics and to evaluate the taxonomic value of these data for species-specific identification. Pollen grains are tricolpate, suboblate to prolate (P/E = 0.81–1.42); medium- or large-sized (P = 49.21–90.44 µm; E = 43.89–93.10 µm). Colpi are long or medium-length, wide at equator, tapered to acute or obtuse ends. Exine sculpture is echinatemicroechinate-nanoechinate; echini (1.00–1.39 µm high) and microechini (0.55–0.98 µm) are conical, with straight or convex sides and acute apices, nanoechini are 0.22–0.46 µm high. Most important characters of taxa diagnostic at species level for the taxonomy are: size of pollen and colpi, exine structure, size of echini and microechini, and pattern of tectum in areas between echini. Pollen grains of C. calcitrapae and C. macrosiphon (sect. Calcitrapa) are generally smaller in size than grains of C. ruber, C. longiflorus and C. kellereri (sect. Centranthus). Pollen of C. kellereri was analysed for the first time in the current study.

Comparison of the Micromorphology and Ultrastructure of Pollen Grains of Selected Rubus idaeus L. Cultivars Grown in Commercial Plantation

The genus Rubus is one of the largest taxonomically diverse and complex genera in the family Rosaceae. Morphology of pollen grains (equatorial and polar axes length, shape and size, aperture position, exine sculpture, perforations) is regarded as one of its main diagnostic features for identification of species and varieties. An attempt was made to fill the gap concerning the pollen micromorphology and ultrastructure of R. idaeus L. using light, scanning, and electron transmission microscopy. This study is a comparative analysis of micromorphological and ultrastructural traits of pollen from six raspberry cultivars. The pollen grains were classified as small or medium of shape prolato-spheroids. The parallel striae in the equatorial view in the exine sculpture were sometimes branched dichotomously in ‘Glen Ample’, ‘Polka’, and ‘Polana’, arcuate in ‘Laszka’ and ‘Pokusa’, or irregularly overlapping in ‘Radziejowa’. The width of exine striae of biennial fruiting cultivars was much larger than in repeated fruiting cultivars. In terms of the increasing number of perforations per unit area of the exine surface, the cultivars were ranked as follows: ‘Pokusa’ < ‘Glen Ample’ < ‘Laszka’ < ‘Polka’ < ‘Polana’ < ‘Radziejowa’. The thickest tectum, the highest and thickest columellae with the largest distances between them, and the thicker foot layer were demonstrated in ‘Glen Ample’. The ectoexine constituted on average ca. 78–90% of the exine thickness. The findings may constitute auxiliary traits i.a. for identification of related taxa, interpretation of phylogenetic relationships, and pollination biology.

Pollen morphology of Teucrium L. (Lamiaceae, Ajugoideae) in Libya

Pollen grains of 11 taxa of Teucrium from Libya were examined using lightmicroscopy (LM) and scanning electron microscopy (SEM) in order to provide better insight on the evaluation of palynological attributes for species characterization of Teucrium with special emphasis on the five Libyan endemic. Two main pollen shapes were documented; subprolate and prolate or perprolate in T. fruticans. The exine sculpture inspected at surface, operculum and pole were mostly verrucate, perforate or scabrate. Teucrium fruticans attained the phenomenon of pollen dimorphism with two distinct shapes and specifics sculpture for each form. The results validated thetaxonomic significance of pollen grains for the discrimination among Teucrium species in Libya.Bangladesh J. Plant Taxon. 24(2): 219–226.

Pollen morphology of Kalmia L. (Phyllodoceae, Ericaceae) and its taxonomic significance

Pollen morphology of seven taxa of Kalmia was examined using light and scanning electron microscopy (LM and SEM, respectively), or SEM alone, in search of new characters that might contribute to infrageneric classification of the genus. The Kalmia species are stenopalynous and characterized by 3-colpor(oid)ate, medium, oblate pollen united in tetrahedral tetrads with rugulate exine sculpture. However, a continuous and serial variation in all the quantitative characters and exine sculpture was revealed within the genus. Kalmia buxifolia is characterized by having the smallest pollen tetrads, largest aperture, largest 2f/D ratio and septum thicker than apocolpial exine. On the other hand, K. latifolia produces the largest pollen tetrads with smallest aperture and smallest 2f/D ratio. An evolutionary trend from rugulate to psilate has also been observed in apocolpial exine sculpture of the genus Kalmia. On the basis of acetolysed pollen characteristics, a dichotomous key for Kalmia was prepared. DOI: http://dx.doi.org/10.3329/bjpt.v19i2.13126 Bangladesh J. Plant Taxon. 19(2): 123-133, 2012 (December)

Morphological studies of pollen grains of the Polish endemic species of the genus Rubus (Rosaceae)

The pollen of six taxa of the genus Rubus endemic to Poland (R. capitulatus, R. chaerophylloides, R. ostroviensis, R. posnaniensis, R. seebergensis and R. spribillei)was studied using light and scanning electron microscopy. The study objective was to extend the knowledge of the species pollen morphology and to investigate whether pollen morphology may help to taxonomically distinguish a very rare bramble species. Study material was derived from six natural localities where the species occur in the Wielkopolska region (Poland). Ten quantitative pollen grain features were analysed as well as the following qualitative ones: outline, shape, type of bridge and exine sculpture. Only mature, correctly formed pollen grains (30 per specimen) were measured and 180 pollen grains were examined in total. It was found that R. capitulatus and R. seebergensis had the highest mean values of P, E and Le features. In addition, pollen grains of R. capitulatus were most flattened (mean P/E ratio equals 1.14), while those of R. seebergensis were most elongated (mean P/E ratio equals 1.27). R. spribillei was the only species with striae of similar width as muri, whereas striae in the remaining species were wider. R. chaerophylloides and R. posnaniensis were characterised by specific, similar exine sculpture. Nevertheless, it should be stated that differences between pollen features of the species studied are so small and the variability of these features are so large that it is difficult to clearly identify the species studied. Therefore, pollen grain morphology can serve only as an auxiliary feature for the determination of these species.

Pollen polymorphism in Thymus capitatus (Lamiaceae)

Polymorphism with respect to size and structural characteristics occurs in pollen grains of several species. Pollen grains of Thymus capitatus (L.) Hoffmans & Link. from three different areas of Greece were collected, and their palynological characteristics were measured. Using light and scanning electron microscopy, a quantification of pollen polymorphism of T. capitatus was achieved by measuring the size and the characteristics of exine sculpture. The measurements were repeated during 3 successive years, and statistical analyses with one-way ANOVA and Duncan’s multiple range test were applied. Results revealed differences in the exine pattern between the locations; also, three palynological characteristics (surface, perimeter, and equatorial diameter) differed statistically. The results clearly indicate that pollen grains of T. capitatus are polymorphic between the sampling areas. The polymorphism has been related to environmental parameters and mainly with water availability. Average rainfall seems to be the main factor contributing to the morphological variation of pollen grains by affecting their size and exine sculpture.