New facts about callose events in the young ovules of some sexual and apomictic species of the Asteraceae family.

Callose (ß-1,3-glucan) is one of the cell wall polymers that plays an important role in many biological processes in plants, including reproductive development. In angiosperms, timely deposition and degradation of callose during sporogenesis accompanies the transition of cells from somatic to generative identity. However, knowledge on the regulation of callose biosynthesis at specific sites of the megasporocyte wall remains limited and the data on its distribution are not conclusive. Establishing the callose deposition pattern in a large number of species can contribute to full understanding of its function in reproductive development. Previous studies focused on callose events in sexual species and only a few concerned apomicts. The main goal of our research was to establish and compare the pattern of callose deposition during early sexual and diplosporous processes in the ovules of some Hieracium, Pilosella and Taraxacum (Asteraceae) species; aniline blue staining technique was used for this purpose. Our findings indicate that callose deposition accompanies both meiotic and diplosporous development of the megaspore mother cell. This suggests that it has similar regulatory functions in intercellular communication regardless of the mode of reproduction. Interestingly, callose deposition followed a different pattern in the studied sexual and diplosporous species compared to most angiosperms as it usually began at the micropylar pole of the megasporocyte. Here, it was only in sexually reproducing H. transylvanicum that callose first appeared at the chalazal pole of the megasporocyte. The present paper additionally discusses the occurrence of aposporous initial cells with callose-rich walls in the ovules of diploid species.

A new sesquiterpenoid and further natural products from Taraxacum portentosum Kirschner & Stepánek, an endangered species.

The chemical studies of roots and aerial parts of Taraxacum portentosum Kirschner & Stepánek, a member of the section Palustria (H. Lindb.) Dahlst. (Asteraceae), led to the isolation of one new eudesmanolide and 13 known compounds, including five sesquiterpenoids: taraxinic acid, 11ß,13-dihydrotaraxinic acid, taraxinic acid ß-glucopyranosyl ester and its 11ß,13-dihydroderivative, ixerin D, one apocarotenoid ‒ loliolide and seven phenolics: scopoletin, 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-1-propanone, methyl p-hydroxyphenylacetate, 5-methoxy-eugenyl-4-O-ß-glucopyranoside, syringin, dihydroconiferin, and dihydrosyringin. Their structures were established by 1H NMR. The new compound was characterized as 3-oxo-4ßH-11,13-eudesmen-12,6-olide-8-O-ß-glucopyranoside based on spectroscopic data (1 D and 2 D NMR) and HRESI mass spectrometry.

Polymorphism of nuclear DNA in selected species of Taraxacum sect. Palustria.

This paper presents the results of research on nuclear DNA polymorphism in six apomictic species of marsh dandelions (Taraxacum sect. Palustria): Taraxacum bavaricum, T. belorussicum, T. brandenburgicum, T. paucilobum, T. subdolum and T. vindobonense. The studies demonstrated the existence of clear genetic differences between species and the existence of nuclear DNA polymorphism within each of the studied species.

Achene micromorphology and its taxonomic significance in some species in Taraxacum sect. Palustria (Asteraceae).

The genus Taraxacum is one of the largest and taxonomically most complicated apomictic genera. Currently, it is considered to consist of over 2800 species placed within 60 sections. Due to the large number of species, and their uniform morphological design and plasticity of leaves, the identification of plants at the species level is challenging even for specialists. This problem significantly hinders the study of their properties and the rational use of these valuable medicinal and nutritional plants. This paper presents the results of research on the morphology and micromorphology of achenes of 28 Taraxacum species of sect. Palustria and for comparison one species per section of: Erythrosperma, Naevosa, Piesis, and Taraxacum. The achenes were measured with a stereoscopic microscope and a biometric program, and micromorphological studies were performed by scanning electron microscopy. It has been shown that traits associated with achene morphology and micromorphology have a high diagnostic value, allowing us to distinguish sections as well as species within the sect. Palustria. Based on the examined achene features, a dichotomous key for determining the studied species was constructed.

Rediscovery of Cyperus flavescens (Cyperaceae) on the northeast periphery of its range in Europe.

In recent years, three large populations of Cyperus flavescens were found in Poland, the richest occurrence of this species in over 30 years. The goal of this research is to determine the habitat factors lead to the mass occurrence of C. flavescens and the present situation of that species and its habitat in Central Europe. Soil conditions of the three populations were studied. To determine the correlation between the occurrence and abundance of species and the chemical parameters of the soil, the DCA and CCA methods were used. The DCA of environmental Ellenberg values was made for all relevés known from Poland. The occurrence of C. flavescens in plant communities in Central Europe was studied. The maximum entropy method was used for potential distribution analysis of C. flavescens. All analyzed traits are important for this species and none has an advantage over another, so the environmental factor affecting the occurrence of C. flavescens is different from the tested. Analysis on Ellenberg values indicate that the longest gradients are temperature, moisture and nutrients. The analysis of vegetation data involving Cyperus flavescens available from Central Europe indicates that this species occurs mainly in the company of Juncus bufonius and Plantago intermedia, whereas other species of the Isoëto-Nanojuncetea class appear rarely. In MaxEnt analysis based on bioclimatic variables, the most important variable is BIO1 (Annual Mean Temperature). The results of our observation indicate that anthropogenic factors such as grazing livestock have a positive effect on the occurrence of the species. It is also very likely that the species is promoted by very warm summers with only short periods of heavy rains. A map of the potential distribution of C. flavescens in Central Europe created according historical and future data show an extension of the range of potential habitats to the north and east.

Environmental Factors Determining the Accumulation of Metals: Cu, Zn, Mn and Fe in Tissues of Taraxacum sp. sect. Taraxacum.

The genus Taraxacum is used in the assessment of soil contamination with heavy metals. There are relatively few studies using sections or species representing this genus. The presented research was conducted in Poland on two habitats, varied in terms of nutrients and metals content. The content of selected metals in leaves and roots of Taraxacum sect. Taraxacum was determined. It was found that in the conditions of increased content of metals in the soil, the analysed species representing sect. Taraxacum accumulate higher amounts of metals in their leaves and roots. Factors of translocation of selected metals from roots to leaves of Taraxacum species, representing the Taraxacum section, are affected by i.a. soil reaction and the content of Corg, Ntot. in the soil. No influence of soil properties on metal biological concentration factor was observed.

Are obligatory apomicts invested in the pollen tube transmitting tissue? Comparison of the micropyle ultrastructure between sexual and apomictic dandelions (Asteraceae, Lactuceae).

With the exception of the sunflower, little information concerning the micropyle ultrastructure of the family Asteraceae is available. The aim of our study was to compare the micropyle structure in amphimictic and apomictic dandelions. Ultrastructural studies using buds and flowers during anthesis have been done on the micropyle of the sexual and apomictic Taraxacum. In all of the species that were examined, the micropylar canal was completely filled with ovule transmitting tissue and the matrix that was produced by these cells. The ovule transmitting tissue was connected to the ovarian transmitting tissue. The micropyle was asymmetrical because the integument epidermis that forms the transmitting tissue was only on the funicular side. There was a cuticle between the obturator cells and epidermal cells on the other side of integument. The micropylar transmitting tissue cells and theirs matrix reached the synergid apex. The cytoplasm of the transmitting tissue cells was especially rich in rough endoplasmic reticulum (ER), dictyosomes, and mitochondria. No major differences were detected between the micropyle structure of the amphimictic and apomictic species; thus, a structural reduction of obturator does not exist. The ovule transmitting tissue is still active in apomictic dandelions despite the presence of the embryo and endosperm. Differences and similarities between the micropyle structure in the Asteraceae that have been studied to date are discussed.

Synergids and filiform apparatus in the sexual and apomictic dandelions from section Palustria (Taraxacum, Asteraceae).

An evolutionary trend to reduce "unnecessary costs" associated with the sexual reproduction of their amphimictic ancestors, which may result in greater reproductive success, has been observed among the obligatory apomicts. However, in the case of the female gametophyte, knowledge about this trend in apomicts is not sufficient because most of the ultrastructural studies of the female gametophyte have dealt with amphimictic angiosperms. In this paper, we tested the hypothesis that, in contrast to amphimictic plants, synergids in apomictic embryo sacs do not form a filiform apparatus. We compared the synergid structure in two dandelions from sect. Palustria: the amphimictic diploid Taraxacum tenuifolium and the apomictic tetraploid, male-sterile Taraxacum brandenburgicum. Synergids in both species possessed a filiform apparatus. In T. brandenburgicum, both synergids persisted for a long time without any degeneration, in spite of the presence of an embryo and endosperm. We propose that the persistent synergids in apomicts may play a role in the transport of nutrients to the embryo.

Structural analysis of 1L-chiro-inositol diester from Taraxacum udum.

1l-1,5-Di-O-p-hydroxyphenylacetyl-chiro-inositol was isolated from the leaves of Taraxacumudum, along with seven other secondary metabolites. Identification of the inositol derivative, based on extensive spectroscopic analyses ((1)H, (13)C and 2D NMR) in two solvents, allowed the correction of previously published data and conformational studies. This is the second report on the presence of inositol esters with p-hydroxyphenylacetic acid in plants.

Sesquiterpenoids and phenolics from roots of Taraxacum udum.

From roots of Taraxacum udum, two new and four known sesquiterpene lactones were isolated, together with five known phenolic compounds. The new compounds were characterized as 11beta, 13-dihydrotaraxinic acid and taraxinic acid 6-O-acetyl-beta-glucopyranosyl ester by spectroscopic methods, especially 1D and 2D NMR, and by comparison with structurally related compounds. The plant material was shown to be a good source of taraxinic acid derivatives.