Comparative micromorphology and anatomy of flowers and floral secretory structures in two Viburnum species

Abstract

In entomogamous plants, the presence and function of floral secretory structures, whose main role is to attract pollinators, is strictly associated with the pollination ecology and hence the reproductive success of the plant. The aims of the present paper were to analyse the micromorphology and anatomy of flower nectaries and stigmas in Viburnum opulus and V. lantana and to determine the function and microstructure of inflorescence trichomes in both taxa using light and scanning electron microscopy as well as histochemical assays. It was found that stigmas were formed by papillae, which contained lipids, polysaccharides, tannins, and pigments. Stigmatic secretion proceeded via cuticular pores. Floral nectaries formed a thick layer around the styles, and nectar was secreted through numerous nectarostomata. There were no traces of vascular bundles penetrating the nectary tissue. In turn, numerous tannin deposits were observed in the cells of the glandular parenchyma. Pedicels, hypanthia, and bracts had mainly peltate and capitate glandular trichomes as well as stellate non-glandular trichomes (in V. lantana). The trichomes were shown to contain lipids, mucilage, and tannins. Many similarities in the flower and nectaries microstructure and considerable heterogeneity were observed in the examined Viburnum species. Knowledge of the microstructural characteristics of flowers, nectaries, and trichomes may be important for the phylogenesis and taxonomy of the genus Viburnum and the family Adoxaceae. Additionally, floral and nectaries features are helpful in assessment of the relatedness between taxa and provide better understanding of the floral biology and pollination ecology.

Developmental Features of Reproductive Organs in Viburnum tinus L.

“…There is a cuticle layer stained by Auramine O which is an indicator of lipoidal substance (Figure 3.4c). Similarly, V. opulus and V. lantana have wet type stigma and stigmatic exudate are rich in organic matter content (Konarska, 2017). Although there are no nuclear disorders before the pollination in papillae cells (Figure 3.4d, e), nuclear fragmentations can be seen after pollination (Figure 3.4f).…”

“…However, disorders and nuclear fragmentations of nuclei are more obvious after the pollination (Figure 3.3o). Stigma is three-lobed and contains papillae as in V. opulus and V. lanatana (Konarska, 2017). Bar: 50 µm (b,f,g,j,k,l,m,n,o) and 100 µm (a, c, d, e, h, i).…”

“…Viburnum tinus L. belongs to the Adoxaceae family comprises more than 200 species of shrubs or small trees. It is mainly used as a medicinal plant and, is preferred in landscape architecture (Konarska, 2017). Viburnum tinus is characterized by a corymb-like inflorescence containing 15-50 flowers.…”

Taxonomic traits in the microstructure of flowers of parasitic Orobanche picridis with particular emphasis on secretory structures

“…This type of nectar secretion has been detected in many plant species from various botanical families (e.g. Papp et al 2013;Antoń et al 2017;Konarska 2017;Jachuła et al 2018).…”

“…Special attention was devoted to the location and structure of floral nectaries and glandular trichomes, i.e. traits that are regarded to be helpful in studies of the taxonomy (relatedness between taxa) and evolution of plants (Behnke 1984;Galetto and Bernardello 2004;Schilmiller et al 2008;Hassan and El-Awadi 2009;Antoń and Kamińska 2015;Konarska 2015Konarska , 2017, and have great importance for the broad-sense ecology of the species, especially the floral biology and interactions between the plant and the pollinator (Anderson 1995;López and Galetto 2002;Silva et al 2016). The ultrastructural studies of O. picridis nectaries present for the first time the function (mode of nectar production and transport) of these glands in the group of parasitic plants.…”