Paolo Gori

Accumulation of polysaccharides in the anther cavity of Allium sativum, clone Piemonte.

Polysaccharides collect naturally in the anther cavity of Allium sativum , clone Piemonte . This occurs during the tetrad stage and involves a conspicuous amount of materials evenly dispersed throughout the entire thecal fluid. The locular polysaccharide content emanates from dictyosomes of the tapetum. The possible meaning of this locular content is discussed.

Ponceau 2R staining on semi‐thin sections of tissues fixed in glutaraldehyde‐osmium tetroxide and embedded in epoxy resins

Proteins were stained (brilliant red) by using 0·5% Ponceau 2R (C.I. 16150) in sulphuric acid (pH 2) at 40°C on sections 1–2 μm thick of tissues fixed in glutaraldehyde‐osmium tetroxide and embedded in epoxy resins. The staining is free from precipitates and does not require the removal of the embedding media.

Development of spherical organelles from the endoplasmic reticulum in the nucellus of some Euphorbia species

SummaryThe development of characteristic cytoplasmic inclusions from endoplasmic-reticulum (ER) cisternae in nucellar cells of some species of Euphorbia has been studied by electron microscopy. The formation of these organelles is preceded by the appearance of rough ER cisternae filled with an electron-dense material and forming complicated networks. Vesicular structures are formed which grow rapidly to give electron-dense, spherical dilations. On the outer surface of their limiting membrane numerous ribosomes and often polysomes are present. This membrane can be seen to remain continuous with the membranes of one or more cisternae of the rough ER up to when the dilations have a maximum diameter of 2.5–3 μ. At this time, continuity between the ER cisternae and the spherical dilations ceases. After this the new cell organelles remain unchanged in size, shape, and electron-density until the cell is disintegrated by the growing embryo-sac. The fate of the contents of these organelles is discussed.

Protein bodies in the nucellus of Euphorbia helioscopia

The nature of electron-dense cytoplasmic organelles in nucellar cells of E. helioscopia has been studied under the electron microscope. Proteolytic tests and selective extractions using different aqueous solutions (NaC1, NaOH, NH 4 OH, HCl, water, and ethanol) defined such nucellar organelles as acid and alkaline-soluble protein bodies. A different sensitivity to alkali was noticed in the protein bodies of different cell layers. Unlike the protein bodies, the contents of the rough endoplasmic reticulum also was found to be soluble in NaCl. The nucellar protein bodies are regarded as a food source for the developing embryo. The hypothesis that certain protein characteristics are modified differently during the storage phase is discussed.

Membrane structures in the integumentary cell walls of the ovule of Nerium oleander.

SummaryUltrastructural changes in the integumentary cell walls of Nerium oleander L. were observed, starting with the beginning of nucellus degeneration. The cell walls in direct contact with the nucellus, followed in a regular progression by those of the next 2–3 cell layers, were seen to increase rapidly in thickness and, in contact with the plasmalemma, to develop a peculiar layer characterized by the presence of numerous membrane-like structures. Morphological and cytochemical findings indicate a membraneous nature of these wall structures; the structures exhibit a marked affinity to potassium permanganate, ruthenium red and phosphotungstic acid, and possess a three-layered configuration. Moreover, the structures were found to be disorganized by phospholipase C. Some of the wall structures appear to be pitted, sac-shaped formations; others to be single sheets. Both types exhibit a direct continuity with the plasmalemma after digestion of the wall material by cellulase. The origin and development of these structures are discussed.

Ponceau 2R staining of proteins and periodic acid bleaching of osmicated subcellular structures on semi-thin sections of tissues processed for electron microscopy: a simplified procedure

An aqueous solution (pH 1·5) of 0·5% Ponceau 2R (C.I. 16150) and 2% periodic acid was used at 318 K to stain proteins (brilliant red) and simultaneously to bleach the osmicated non‐proteinaceous cell structures on 1–2 μm thick sections of tissues fixed in glutaraldehyde‐osmium tetroxide and embedded in epoxy resins. This H5IO6 bleaching‐Ponceau 2R staining procedure only stains the proteins so that black‐and‐white films can be used.

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.

Ferritin in the integumentary cells of Oxalis corniculata

Ferritin was detected in the integumentary cells of the Oxalis corniculata ovule by means of electron microscope X-ray microanalysis. It occurs in immature plastids and in amyloplasts in the form of paracrystalline aggregates which have round profiles or which may be indented by the surrounding starch grains. Integumentary ferritin aggregates are regarded as an iron source for the embryo.

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.