Micromorphology and anatomy of the flower of Zephyranthes candida (Amaryllidaceae)

The use of morphological features of flowers in the taxonomy of plants is becoming increasingly important. The structure of the Zephyranthes candida (Lindl.) Herb. flowers on permanent cross-sectional and longitudinal sections was studied using a light microscope. The genus Zephyranthes belongs to the subtribe Hippeastrinae Walp. tribe Hippeastreae Sweet., family Amaryllidaceae s.l. Microscopic studies of the flower are considered as a tool to identify hitherto unknown structural adaptations of plants to specialized pollination methods and to elucidate the first stages of fruit morphogenesis, as many features of the fruit appear at the flower stage. The morphometric parameters, morphology, anatomy, and vascular anatomy of the ovary were described by using the flower’s transverse sections. Ten flowers of Z. candida were sectioned using standard methods of Paraplast embedding and serial sectioning at 20 μm thickness. Sections were stained with Safranin and Astra Blau and mounted in Eukitt. It was found that in the studied species the tepals have multi-bundle traces of 10–12 leading bundles. We consider the gynoecium of the studied species to be eusincarpous. The vascular system of the inferior ovary consists of three dorsal and three septal bundles, paired ventral bundles of carpels, which form ovule traces. For the first time, the presence of the following gynoecium zones was detected: a synascidiate structural zone with a height of about 360 μm and a fertile symplicate structural zone with a height of about 1560 μm and a hemisymplicate zone of 480 μm. Septal nectaries appear in the hemisymplicate zone and open with nectary split at the base of the style, the total height of the septal nectary is 760 μm. The ovary roof is 280 μm. Bifurcated dorsal and septal bundles of carpels have been identified, which can be considered as adaptations of the early stages of fruit morphogenesis to opening. Anatomical features of the ovary of Z. candida are numerous vascular bundles in the pericarpium, non-lignified endocarp at the flower stage, we consider as adaptations to the formation of juicy fruit. New data on the anatomical structure of the flower are a significant addition to the information on antecological and post-anthetic features of the studied species. Also, these data can be used in the construction of parsimony branches of the family Amaryllidaceae.

The flower morphology in three Convallariaceae species with various attractive traits

<p>The general morphology and micromorphology of the flower in <em>Polygonatum multiflorum</em>, <em>Maianthemum bifolium</em>, and <em>Convallaria majalis</em> were studied using light microscopy methods. Among the studied species, <em>P. multiflorum</em> and <em>C. majalis</em> have syntepalous and trimerous flowers, and in <em>M. bifolium</em> flowers are the most reduced: they are dimerous, pentacyclic, and with free tepals. Only in <em>P. multiflorum</em> stamens are considerably adnate to the floral tube. The gynoecium of <em>P. multiflorum</em> consists of synascidiate, hemisymplicate, and asymplicate zones. In the gynoecium of <em>M. bifolium</em> and<em> C. majalis</em>, synascidiate, symplicate, and asymplicate vertical zones were revealed. In <em>P. multiflorum</em> and <em>M. bifolium</em>, the style is composed of postgenitally connated carpels, while in <em>C. majalis</em> the style is formed by congenitally fused carpels (symplicate gynoecium zone). A common pattern of the venation of the floral parts was revealed in all the species.</p><p>The external flower morphology and the gynoecium inner structure are different in all three species, providing adaptations for the pollination mode. Attractive elements observed in the flower of <em>P. multiflorum</em> are the long septal nectary in the ovary and epidermal trichomes on the inner perigonium surface and on the filaments. In <em>M. bifolium</em>, a rudimentary external septal nectary was observed for the first time. No nectaries or other morphologically distinct secretory structures were found in the <em>C. majalis</em> flower, allowing considering the <em>C. majalis</em> flowers as pollen flowers.</p>

The gynoecium structure in Dracaena fragrans (L.) Ker Gawl., Sansevieria parva N.E. Brown and S. trifasciata Prain (Asparagaceae) with special emphasis on the structure of the septal nectary

In the gynoecium of <em>Dracaena fragrans</em>, <em>Sansevieria</em> <em>parva </em>and <em>S. trifasciata</em>, the vertical zonality of the ovary, the structural zonality of the gynoecium following Leinfellner, and the zonality of the septal nectary were studied. The ovary structure is characterised by a high parenchymatous ovary base and ovary roof as well as a long septal nectary that can be extended in both of them and opens with secretory nectary splits. The gynoecium of these species has a short synascidiate zone, a fertile hemisynascidiate zone with a median ovule attached, a hemisymlicate zone (only in <em>D. fragrans</em>) and an asymplicate zone (with postgenitally fused carpels) that comprises the ovary roof, common style and stigma. In the septal nectary, we detected three vertical zones: the basal zone of the distinct nectary in the ovary base or/and the synascidiate zone, the zone of the common nectary (in the hemisynascidiate and hemisymlicate zones) and the zone of the external nectary (the nectary splits in the asymplicate zone). The gynoecium structure in the studied species shows differences in the length of the gynoecium and septal nectary zones and also in the interrelationships of all these three types of vertical zonality.

Nectary structure and nectar presentation in the Mediterranean geophyte, Urginea maritima (Hyacinthaceae)

The morphology, anatomy, and ultrastructure of the floral nectary of Urginea maritima (L.) Baker were investigated at three stages of nectary development. The plant possesses a typical gynopleural (septal) nectary with secondary presentation. The nectary consists of one layer of epithelium secretory cells and one to four layers of subsidiary cells subtended by two to six layers of parenchyma (subnectary) cells. The nectary releases the nectar at a point two-thirds towards the summit of the ovary by means of carpellary sutures. Nectar secretion appears to depend largely on the hydrolysis of starch grains stored in amyloplasts at the intermediate stage. The hydrolysis process most likely commences in the epithelium layer followed by the subsidiary tissue and then the parenchyma cells of the ovary wall. A symplastic transfer of the secreted nectar occurs by plasmodesmata connecting the subsidiary cells to the parenchyma and the epithelial secretory cells. However, microchannels in the cell wall of the epithelial cells may facilitate the apoplastic transfer of the nectar into the nectary cavity. The old stage of nectary development is characterized by a crystallized form of nectar, collapse of the parenchyma cells, complete starch hydrolysis, and disappearance of the amyloplasts and endoplasmic reticulum.

The secretory glands of Asphodelus aestivus flower

Various secretory glands are observed on Asphodelus aestivus flower, a common geophyte of Mediterranean type ecosystem. The floral nectary has the form of individual slits between the gynecium carpels (septal nectary). The septal slits extend downwards to the ascidiate zone of the carpels. The nectar is secreted by the epidermal cells of the slits, which differentiate into epithelial cells. The latter contain numerous organelles, among which endoplasmic reticulum elements and golgi bodies predominate. Nectar secretion results in an expansion of the space between the septa. The nectar becomes discharged through small holes on the ovary wall. Six closely packed stamens surround the ovary and bear numerous papillae at their basis. These papillae are actually osmophores, i.e. secretory structures responsible for the manufacture, secretion and dispersion of terpenic scent. A mucilage gland (obturator) exists between the lateral ovule and the ovary septa, giving a positive reaction with Schiff’s reagent. This gland secretes a mucoproteinaceous product to nourish the pollen tube and to facilitate its penetration into the ovary.