Simonetta Muccifora

Effects of copper on germination and reserve mobilization in Vicia sativa L. seeds

The effects of different copper concentrations on percentage germination, increase in fresh weight and radicle growth of Vicia sativa L. seeds were studied. Physiological studies showed that the germination rate was not affected up to a concentration of 5 × 10⁻³ M, but already at 10⁻³ M the copper stopped root elongation. Structural and ultrastructural observations of embryo and cotyledon reserve mobilization showed that inhibition of radicle growth at 10⁻³ M Cu concentration cannot be ascribed to nutrient shortage but probably to an effect of copper on radicle cell division and elongation. In seeds treated with 5 × 10⁻³ M CuBr₂, the copper completely inhibited cotyledon protein mobilization, so that embryo protein mobilization supported normal growth of the radicle up to 30 h after imbibition. The particular protein content of adjacent cotyledon cells is also discussed.

An ultrastructural study of the mature spermatozoid of the fern Asplenium trichomanes L. subsp. trichomanes

Abstract Asplenium trichomanes L. subsp. trichomanes spermatozoids are spirals of about five turns. Keels link the elements of the microtubular ribbon with the plates of the lamellar layer (LL) which are uninterrupted, parallel and curved with an inner angle of about 150°. Electron-opaque filaments connect the microtubules of the multilayered structure (MLS) and the osmiophilic crest, the LL and the MLS-associated mitochondrion and the latter and the plasmalemma. The nucleus occupies the 2.5–3 posterior turns and has an inner honeycomb-shaped chromatin mass and an outer highly condensed chromatin mass with randomly scattered electron-transparent areas. The basal bodies of the ca. 50 flagella are bounded by a reticulum of granular material which forms a plug inside their proximal region; the proximal region of the flagellum has a 9 + 0 pattern. The axoneme has a 9 + 2 pattern.

Ultrastructural features of spermatocytes and spermatozoids in the fern Phyllitis scolopendrium (L.) Newm. subsp. scolopendrium

Abstract Phyllitis scolopendrium Newm. subsp. scolo-pendrium spermatozoids are cells 10 µm long in the form of spirals with about four turns. Their chromatin is partly honeycomb-shaped and partly highly condensed. The nuclear envelope over the latter has a regular, thin intermembrane space crossed by fibers that are probably involved in connecting the chromatin with elements of the microtubular ribbon. The cytoplasm is traversed by long cistern-shaped folds of the plasma membrane, believed to be involved in a late process of cell simplification through segregation and detachment of parts of the cytoplasm. The spermatozoids are embedded in 1–1.5 µm thick amorphous electron-transparent material containing cellulose fibrils. These fibrils are considered a network connected to the original spermatocyte wall and elements of elastic support for the amorphous material. The different polysaccharide composition of the inner and outer parts of the walls causes changes in the size and shape of the ring cells, so that the spermatozoids are pushed against and past the cap cell. The gametes are released through limited laceration of the cap cell. The laceration is due to the generally weak substructure of the cell wall. A light microscope sequence of spermatozoid release and scanning electron microscope features of newly released spermatozoids are shown.

Analysis of extracellular vesicles produced in the biofilm by the dimorphic yeast Pichia fermentans

The yeast Pichia fermentans DISAABA 726 strain (P. fermentans) is a dimorphic yeast that under different environmental conditions may switch from a yeast‐like to pseudohyphal morphology. We hypothesize that exosomes‐like vesicles (EV) could mediate this rapid modification. EV are membrane‐derived vesicles carrying lipids, proteins, mRNAs and microRNAs and have been recognized as important mediators of intercellular communication. Although it has been assumed for a long time that fungi release EV, knowledge of their functions is still limited. In this work we analyze P. fermentans EV production during growth in two different media containing urea (YCU) or methionine (YCM) where yeast‐like or pseudohyphal morphology are produced. We developed a procedure to extract EV from the neighboring biofilm which is faster and more efficient as compared to the widely used ultracentrifugation method. Differences in morphology and RNA content of EV suggest that they might have an active role during dimorphic transition as response to the growth conditions. Our findings are coherent with a general state of hypoxic stress of the pseudohyphal cells.

Response to copper bromide exposure in Vicia sativa L. seeds: analysis of genotoxicity, nucleolar activity and mineral profile.

Copper bromide (CuBr2) effects on seed germination and plantlet development of Vicia sativa L. are evaluated through mitotic index, chromosome aberrations, nucleolar activity and mineral profile. CuBr2 induces a significant presence of micronuclei, sticky and c-metaphases, anaphase bridges and chromosome breaks. Increased number of nucleoli and scattering of AgNOR proteins from the nucleolus in the nuclear surface at CuBr2 1mM and in the cytoplasm at CuBr2 5mM, goes along with the decrease of root growth. In V. sativa embryo the content of many macro and micronutrients increases up to copper 1mM in agreement with reserve mobilization while at CuBr2 5mM some elements are present in lower amount. We hypothesize that inhibitory effects observed at 5mM are due either to a nutrient shortage or to a direct influence of copper on root cell division, evidenced by low mitotic index, high occurrence of chromosome aberrations and loss of material from the nucleolus.

Asplenium trichomanes ssp. trichomanes gametophyte. A light and electron microscope study

SUMMARYIn controlled culture conditions Asplenium trichomanes L. ssp. trichomanes spores germinate 8–10 days after sowing. The first protonemal cell and the primary rhizoid arise from two unequal divisions of the original spore cell. First an unbranched 5–6-celled germ forms which later becomes a spatula-, racket- and finally heart-shaped, bisexual prothallus with archegonia consisting of four rows of four cells and antheridia consisting of opercular, ring and basal cells. An additional notch with associated archegonia and antheridia develops in several-month-old gametophytes. The ultrastructure of the mature gametophyte is characterized by pleomorphic mitochondria, plastids which may be chloroamyloplasts, vacuoles containing osmiophilic materials and poorly developed endoplasmic reticulum of smooth type. The walls are crossed by many plasmodesmata. (Membrane) structures are visible inside the wall materials nearest the plasmalemma.

Ultrastructure, Viability, and In Vitro Germination of the Tricellular Sambucus nigra L. Pollen

Mature pollen grains of Sambucus nigra L. are tricolporate, isopolar, 12.5 μm wide, 25 μm long, and tricellular. They have a tectate exine, a bilayered nexine, and a thin intine. The vegetative cell has abundant rough endoplasmic reticulum, many well‐structured mitochondria, numerous apparently inactive dictyosomes, immature dividing, and starch‐filled plastids and lipid bodies. The sperm cells have few and poorly structured organelles. They are linked by cytoplasmic bridges, indicating a persistent physiological unit, and are surrounded by fibrillar polysaccharide material. Freshly released pollen is 95% viable. Three‐ and 4‐year‐old pollen grains stored at −20°C are 78.2% and 43% viable, respectively. In vitro germination requirements and pollen tube growth are more similar to those of bicellular pollen than to those of tricellular pollen.

Nuclear Paracrystals in the Fern Polystichum setiferum Gametophyte

Single nuclear paracrystals were observed in gametophyte cells of the fern Polysti- chum setiferum. They consist of proteins poor in basic aminoacids and have sharp-profiled, poly- hedral shapes, with inner diameters up to 4.5 p.m. The substructure is a fine, very close-meshed reticulum resolvable at magnifications of 40,000X or more. The hypothesis that these paracrystals are storage bodies of unused nuclear proteins is discussed.

An integrated approach to highlight biological responses of Pisum sativum root to nano-TiO2 exposure in a biosolid-amended agricultural soil

This study focused on crop plant response to a simultaneous exposure to biosolid and TiO2 at micro- and nano-scale, being biosolid one of the major sink of TiO2 nanoparticles released into the soil environment. We settled an experimental design as much as possible realistic, at microcosm scale, using the crop Pisum sativum. This experimental design supported the hypotheses that the presence of biosolid in the farming soil might influence plant growth and metabolism and that, after TiO2 spiking, the different dimension and crystal forms of TiO2 might be otherwise bioavailable and differently interacting with the plant system. To test these hypotheses, we have considered different aspects of the response elicited by TiO2 and biosolid at cellular and organism level, focusing on the root system, with an integrative approach. In our experimental conditions, the presence of biosolid disturbed plant growth of P. sativum, causing cellular damages at root level, probably through mechanisms not only oxidative stress-dependent but also involving altered signalling processes. These disturbances could depend on non-humified compounds and/or on the presence of toxic elements and of nanoparticles in the biosolid-amended soil. The addition of TiO2 particles in the sludge-amended soil, further altered plant growth and induced oxidative and ultrastructural damages. Although non typical dose-effect response was detected, the most responsiveness treatments were found for the anatase crystal form, alone or mixed with rutile. Based on ultrastructural observations, we could hypothesise that the toxicity level of TiO2 nanoparticles may depend on the cell ability to isolate nanoparticles in subcellular compartments, avoiding their interaction with organelles and/or metabolic processes. The results of the present work suggest reflections on the promising practice of soil amendments and on the use of nanomaterials and their safety for food plants and living organisms.

An electron microscope study of gametangia in the green seaweed Halimeda tuna

Abstract The gametangia of the green seaweed Halimeda tuna are spherical bodies of diameter up to 250–300 μm. They are clustered in groups of 8–10 on hundreds of threads sprouting from all pale white segments of the fertile individuals. In addition to gametes, starch-containing chloroplasts, naked starch grains and two types of spherical bodies different in size and ultrastructure are the main corpuscular components. A layer of amorphous material of irregular thickness underlies the walls which are finely and evenly rough, structureless, electron translucent and 1–1.5 μm thick. Gametangia with superficial wall warts were found also.