Variation in seed morphology in the genus Erica L. (Ericaceae)
Seed morphology was studied in 136 species of Erica, including 123 from South Africa (Cape Floristic Region), 5 from tropical Africa, and 8 from Europe. Seed anatomy was studied in 13 selected species by light and scanning electron microscopy. Seed morphology of each species was described and documented by SEM micrographs. Ten major diagnostic features were selected, concerning seed shape, primary sculpture, and fine relief. On the basis of these features, the species were divided into 14 groups. Within them, 40 morphologically homogeneous subgroups were distinguished, which could possibly be used in future revisions of the genus. A key to species identification has been developed on the basis of seed characteristics. A very close similarity was observed between seeds of some Erica species from distant parts of the distribution range of this genus.
Hypericum elegans is a rare perennial distributed primarily in Central and Eastern Europe. Seed morphology and anatomy in H. elegans was studied on the basis of a seed sample from its only locality in Poland. Scanning electron microscopy revealed that the seed coat of mature seeds is composed basically of 3 cell layers: epidermal, subepidermal and sclerenchymatic. They are documented graphically here.
Eight Hypericum species are native to Poland: H. elegans Stephan ex Willd., H. hirsutum L., H. humifusum L., H. maculatum Crantz, H. montanum L., H. perforatum L., H. pulchrum L., and H. tetrapterum Fr. Only seeds of H. elegans were investigated in detail in Poland before, so here we present results of qualitative and quantitative analyses of seed morphology of the other 7 species, based on characters like seed length, width, and shape, seed coat sculpture, shape of epidermal cells of the testa, and number of epidermal cells along the seed axis. The results show that seeds of the studied species are small, 0.56-1.15 mm long and 0.26-0.49 mm wide. In SEM images, seed coat sculpture is reticulate in 5 species, papillate in H. hirsutum, and cup-shaped in H. pulchrum. The differences are caused by the varied final development of the testa epidermis, which constitutes the outer layer of the seed coat. The mean number of epidermal cells along the seed axis ranges from 22 to 33. Results of cluster analysis, based on the agglomeration method and including also published data on seeds of H. elegans, show that the variation in the investigated characters of seeds is reflected in the taxonomic division of the genus into sections.
The article concerns the issue of using imagery reconnaissance sensors for the identification of geological-engineering conditions in river channels, in the aspect of evaluating the forcing of a water obstacle. It discusses the issues associated with using air platforms (manned and unmanned) in remote sensing surveying of selected fragments of the Vistula and Bug river channels and the correct interpretation of the obtained results, through their verification using bathymetric tests conducted directly in the river channels.
The rpo genes are characterized by rapidly-evolving sequences. They encode subunits of plastid-encoded (PEP) polymerase (rpoA, rpoB, rpoC1 and rpoC2). This polymerase is one of the most important enzymes in the chloroplasts. The primary aim of the research was to study the rate of molecular evolution in the rpo genes and to estimate these genes as phylogenetic markers based on the example of the genus Erica (Ericaceae). The tested rpo genes demonstrated similarities on multiple levels, for example: phylogenetic informativeness, variation level, intragenic mutation rates and the effect of intragenic mutations on the properties of encoded peptides. This study did not confirm that the analyzed rpo genes are reliable markers and may be helpful in understanding phylogenetic relationships between species that belong to the same genus. The rpoC2 gene was found to be a most useful phylogenetic marker in the Erica genus, while rpoC1 was found to be the least promising gene.
Hypericum majus (A. Gray) Britton is an alien species for Europe. It originates from North America and, in recent years, has been spreading in Europe. Presently, this species is found in Germany, France, Italy, Bosnia and Herzegovina, and Belarus. In Poland, it was noted for the first time in 2017 in western part of the country. Thus far, no detailed morphology and anatomy of H. majus seeds based on light and electron microscopy studies has been presented. Considering the fact that seeds provide important taxonomical information and the discussed species has not been investigated in this respect, in this research, an attempt was made to broaden the present knowledge.
Investigations were conducted based on samples originating from three localities in Central Europe (Poland). The obtained results showed that H. majus seeds are very small – about 0.5 mm in length. In the SEM image, their surface is reticulate, typical of majority of species in this genus. Anatomical analysis showed that seed coat of matured seeds is very delicate, composed of two cell layers with strongly lignified walls.