Bartosz J. Płachno

Unusual embryo structure in viviparous Utricularia nelumbifolia, with remarks on embryo evolution in genus Utricularia

In most species of the Genlisea–Utricularia sister lineage, the organs arising directly after germination comprise a single leaf-like structure, followed by a bladder-trap/stolon, with the lack of an embryonic primary root considered a synapomorphic character. Previous anatomical work suggests that the most common recent ancestor of Utricularia possessed an embryo comprising storage tissue and a meristematic apical region minus lateral organs. Studies of embryogenesis across the Utricularia lineage suggest that multiple primary organs have only evolved in the viviparous Utricularia nelumbifolia, Utricularia reniformis, and Utricularia humboldtii within the derived Iperua/Orchidioides clade. All three of these species are specialized for growth as “aquatic epiphytes” in the tanks of bromeliads, with recent phylogenetic evidence suggesting the possibility that multiple primary organs may have evolved twice independently within this clade. The primary organs of viviparous Utricularia also possess epidermal surface glands, and our study suggests that these may function as root hairs for uptake of solutes from the external environment—a possible adaptation for the “aquatic–epiphytic” habitat.

Functional anatomy of the ovule in Genlisea with remarks on ovule evolution in Lentibulariaceae

The Lentibulariaceae are highly evolved and specialized carnivorous angiosperms displaying not only unusual morphology and embryology but also specific changes in the genome and chromosomes as large as bacterial chromosomes. Comparative study of the morphology and detailed anatomy of the ovule in the genera Genlisea, Utricularia, and Pinguicula should shed new light on the phylogeny of this family. The clade Genlisea + Utricularia is sister to the genus Pinguicula, which is considered the most primitive taxon within Lentibulariaceae. Thus we should expect the ovules of Genlisea to be more similar to those of the more closely related genus Utricularia than to Pinguicula. Surprisingly, the ovules of Genlisea retain characters (free funiculus, ES remaining in the ovule) in common with Pinguicula, presumably inherited from a common ancestor. Genlisea ovules have only one main character in common with subgenus Polypompholyx (Utricularia): a well-developed funiculus. There are differences between the ovules of the subgenera Genlisea and Tayloria. In subgenus Genlisea the micropyle tends to be closer to the funiculus and the ovule forms an unusual jacket-like nutritive tissue of integumental origin. The most specialized ovules in Lentibulariaceae evolved in the genus Utricularia. The special chalazal nutritive tissue in Genlisea and Utricularia is simply a hypostase.

Anatomy of ovary and ovule in dandelions (Taraxacum, Asteraceae)

The genus Taraxacum Wigg. (Asteraceae) forms a polyploid complex within which there are strong links between the ploidy level and the mode of reproduction. Diploids are obligate sexual, whereas polyploids are usually apomictic. The paper reports on a comparative study of the ovary and especially the ovule anatomy in the diploid dandelion T. linearisquameum and the triploid T. gentile. Observations with light and electron microscopy revealed no essential differences in the anatomy of both the ovary and ovule in the examined species. Dandelion ovules are anatropous, unitegmic and tenuinucellate. In both sexual and apomictic species, a zonal differentiation of the integument is characteristic of the ovule. In the integumentary layers situated next to the endothelium, the cell walls are extremely thick and PAS positive. Data obtained from TEM indicate that these special walls have an open spongy structure and their cytoplasm shows evidence of gradual degeneration. Increased deposition of wall material in the integumentary cells surrounding the endothelium takes place especially around the chalazal pole of the embryo sac as well as around the central cell. In contrast, the integumentary cells surrounding the micropylar region have thin walls and exhibit a high metabolic activity. The role of the thick-walled integumentary layers in the dandelion ovule is discussed. We also consider whether this may be a feature of taxonomic importance.

Cytoarchitecture of Utricularia nutritive tissue

Beginning with light microscopy studies in the late 19th century, the placental “nutritive tissue” in carnivorous plants of Utricularia spp. has been well described by several authors. Based on observations of direct contact between the embryo sac and the “nutritive tissue” and the lack of vascularization of the ovule, it has been suggested that this nutritive tissue plays a key role in the nutrition of the female gametophyte. To date, however, the structure of this tissue has received only scant attention. To fill this knowledge gap, we have characterized its anatomy and histochemistry in more detail and addressed the speculations of a number of earlier researchers. Nutritive tissue during the period of flower opening in three Utricularia species, each belonging to different sections and subgenera (Polypompholyx, Bivalvaria and Utricularia), was examined by light and, in particular, electron microscopy. In all of the investigated species, nutritive tissue cells differ from placental parenchyma cells in having no huge vacuole, no large amyloplasts with starch grains, and no protein inclusions in the nucleus. The funicular nutritive tissue in U. dichotoma consists of active cells with a secretory character, while U. sandersonii has a small placental nutritive tissue consisting of colenchymatous cells accumulating lipids. The most complex nutritive tissue occurs in aquatic U. intermedia, which occupies a derived position in the genus phylogeny. In this latter species, the cells of this tissue resemble meristematic cells in having a relatively large nucleus, thin cell walls, and reduced vacuoles, but the well-developed endoplasmic reticulum (ER) in some cells is similar to that in secretory cells. The cytoplasm is rich in microtubules, some of which are in close contact with the ER cisternae. We found very thick cell walls between nutritive tissue cells and parenchyma cells, but plasmodesmata between these types of cells are rare. Similarities in both the position and structure of nutritive tissue in Polypompholyx and section Pleiochasia support their classification together in one subgenus, based on results from a molecular study. The position and structure of the nutritive tissue in Utricularia spp. are related to the position of various species in the genus phylogeny.

Mineral nutrient uptake from prey and glandular phosphatase activity as a dual test of carnivory in semi-desert plants with glandular leaves suspected of carnivory

BACKGROUND AND AIMS Ibicella lutea and Proboscidea parviflora are two American semi-desert species of glandular sticky plants that are suspected of carnivory as they can catch small insects. The same characteristics might also hold for two semi-desert plants with glandular sticky leaves from Israel, namely Cleome droserifolia and Hyoscyamus desertorum. The presence of proteases on foliar hairs, either secreted by the plant or commensals, detected using a simple test, has long been considered proof of carnivory. However, this test does not prove whether nutrients are really absorbed from insects by the plant. To determine the extent to which these four species are potentially carnivorous, hair secretion of phosphatases and uptake of N, P, K and Mg from fruit flies as model prey were studied in these species and in Roridula gorgonias and Drosophyllum lusitanicum for comparison. All species examined possess morphological and anatomical adaptations (hairs or emergences secreting sticky substances) to catch and kill small insects. METHODS The presence of phosphatases on foliar hairs was tested using the enzyme-labelled fluorescence method. Dead fruit flies were applied to glandular sticky leaves of experimental plants and, after 10-15 d, mineral nutrient content in their spent carcasses was compared with initial values in intact flies after mineralization. KEY RESULTS Phosphatase activity was totally absent on Hyoscyamus foliar hairs, a certain level of activity was usually found in Ibicella, Proboscidea and Cleome, and a strong response was found in Drosophyllum. Roridula exhibited only epidermal activity. However, only Roridula and Drosophyllum took up nutrients (N, P, K and Mg) from applied fruit flies. CONCLUSIONS Digestion of prey and absorption of their nutrients are the major features of carnivory in plants. Accordingly, Roridula and Drosophyllum appeared to be fully carnivorous; by contrast, all other species examined are non-carnivorous as they did not meet the above criteria.

Feeding behaviour of carnivorous Genlisea plants in the laboratory

Abstract Genlisea is a terrestrial carnivorous plant which occurs mainly in nutrient-poor soil. It has been known that individuals of ciliates Paramecium caudatum are trapped and digested by this plant. Our observations show that Genlisea can trap not only Protozoa but also bigger animals, that their prey depend on the kind of available organisms and that prey were trapped passively. In the laboratory, Genlisea traps contained a variety of organisms: bacteria, algae, protozoans, nematodes, rotifers, annelids, tardigrades, crustaceans and mites.

Cuticular discontinuities in glandular hairs of Genlisea St.-Hil. in relation to their functions

Abstract The terminal cells of glandular hairs are shown to be the only permeable sites on the trap surface. A cuticle of these cells of internal hairs forms pores. These discontinuities can be demonstrated directly by SEM and indirectly by using a vital stain. Cuticular discontinuities of internal trap hairs are involved in the discharge of hydrolytic enzymes and the absorption of the products of the digestion (internal trap nutrients absorption). For external trap hairs was suggested that they are hydropoten and play a role in both water and ions transport (external trap nutrients and water absorption). In some Genlisea species, sessile hairs on the underground parts may play a role in water transpiration. In other species like Genlisea filiformis and G. aurea, these hairs produce mucilage which is a habitat of the community of microorganisms.

New data about the suspensor of succulent angiosperms: Ultrastructure and cytochemical study of the embryo-suspensor of Sempervivum arachnoideum L. and Jovibarba sobolifera (Sims) Opiz.

The development of the suspensor in two species — Sempervivum arachnoideum and Jovibarba sobolifera — was investigated using cytochemical methods, light and electron microscopy. Cytological processes of differentiation in the embryo-suspensor were compared with the development of embryo-proper. The mature differentiated suspensor consists of a large basal cell and three to four chalazal cells. The basal cell produces haustorial branched invading ovular tissues. The walls of the haustorium and the micropylar part of the basal cell form the wall ingrowths typical for a transfer cells. The ingrowths also partially cover the lateral wall and the chalazal wall separating the basal cell from the other embryo cells. The dense cytoplasm filling the basal cell is rich in: numerous polysomes lying free or covering rough endoplasmic reticulum (RER), active dictyosomes, microtubules, bundles of microfilaments, microbodies, mitochondria, plastids and lipid droplets. Cytochemical tests (including proteins, insoluble polysaccharides and lipids are distributed in the suspensor during different stages of embryo development) showed the presence of high amounts of macromolecules in the suspensor cells, particularly during the globular and heart-shaped phases of embryo development. The protein bodies and lipid droplets are the main storage products in the cells of the embryo-proper. The results of Auramine 0 indicate that a cuticular material is present only on the surface walls of the embryo-proper, but is absent from the suspensor cell wall. The ultrastructural features and cytochemical tests indicate that in the two species — S. arachnoideum and J. sobolifera — the embryo-suspensor is mainly involved in the absorption and transport of metabolites from the ovular tissues to the developing embryo-proper.

Are there symplastic connections between the endosperm and embryo in some angiosperms? : a lesson from the Crassulaceae family

It is believed that there is symplastic isolation between the embryo (new sporophyte) and the endosperm (maternal-parental origin tissue, which nourishes the embryo) in angiosperms. However, in embryological literature there are rare examples in which plasmodesmata between the embryo suspensor and endosperm cells have been recorded (three species from Fabaceae). This study was undertaken in order to test the hypothesis that plasmodesmata between the embryo suspensor and the endosperm are not so rare but also occur in other angiosperm families; in order to check this, we used the Crassulaceae family because embryogenesis in Crassulaceae has been studied extensively at an ultrastructure level recently and also we tread members of this family as model for suspensor physiology and function studies. These plasmodesmata even occurred between the basal cell of the two-celled proembryo and endosperm cells. The plasmodesmata were simple at this stage of development. During the development of the embryo proper and the suspensor, the structure of plasmodesmata changes. They were branched and connected with electron-dense material. Our results suggest that in Crassulaceae with plasmodesmata between the endosperm and suspensor, symplastic connectivity at this cell–cell boundary is still reduced or blocked at a very early stage of embryo development (before the globular stage). The occurrence of plasmodesmata between the embryo suspensor and endosperm cells suggests possible symplastic transport between these different organs, at least at a very early stage of embryo development. However, whether this transport actually occurs needs to be proven experimentally. A broader analysis of plants from various families would show whether the occurrence of plasmodesmata between the embryo suspensor and the endosperm are typical embryological characteristics and if this is useful in discussions about angiosperm systematic and evolution.

Comparative morphology of the male genitalia of Aphididae (Insecta, Hemiptera): part 1

The present study provides new data related to the morphology of the male genitalia of Aphididae. The structure of the male genitalia of 39 species from 23 genera of Aphididae was studied using light and scanning electron microscopy. In the species studied, the genitalia of males consist of a phallus composed of the sclerotized basal part with its articulation and a membranous apical part—an aedeagus as well as parameres. This state probably represents the hypothetical plesiomorphic condition of the external male genitalia of aphids. According to the results of the present study, the male genitalia vary among subfamilies (the most varied in Lachninae). Both the phallus and parameres show great variability in their form and the number of setae and may provide characters of taxonomic and diagnostic importance. The shape, size, and modification of parameres are considered in conjunction with the phylogenetic relationships among the studied taxa. Compared with Lachninae, Greenideinae, Aiceoninae, the external genitalia of Aphidinae are less specialized, having many features in common with those of drepanosiphine aphids and differing little from the hypothetical condition. In dwarfish males of Anoeciinae, Thelaxinae, Hormaphidinae, and Eriosomatinae, the miniaturization of the body size affects on the modification of genitalia, mostly parameres. However, the homology of non-modified and modified structures of parameres is not clear.