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Asplenium trichomanes ssp. trichomanes gametophyte. A light and electron microscope study
No full textIn 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. © 1995 Taylor & Francis Group, LLC
A scanning and transmission electron microscope study of gametangia in the green seaweed 'Halimeda tuna
No full textThe 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. © 1994 Taylor & Francis Group, LLC
Protein Characterization of Protein Bodies from Cotyledons of Mucuna pruriens (L.) DC
No full textSeeds of Mucuna pruriens (L.) DC. (Fabaceae) were analyzed for protein composition of protein bodies isolated from cotyledons. Protein bodies were successfully separated by Lympholyte and those of dry seeds, observed by scanning electron microscope, were elliptical or spherical in shape with a diameter of 5-12 μm. Protein content in dry seed protein bodies was 10.6 mg/g dry weight. Globulin was the largest protein fraction isolated (62.5 %), followed by albumin (18.3 %), glutelin (15.8 %) and prolamin (3.4 %). The prolamin fraction and high glutelin content are uncommon in legumes. SDS-PAGE of albumins, globulins, prolamins and glutelins provided different band numbers and molecular weights under reducing and non reducing conditions and suggested that the albumin fraction is rich in disulphide bonds. © 2013 Springer Science+Business Media New York
Influence of seed coat color on germination rate and seedling development of Trifolium repens. Is physiological dormancy possible?
Full text linkTrifolium repens L. (var. Regal Ladino) is among the most used species of Italian legumes as fodder
for pastures, for direct consumption, or as mowing for stocks and then pastures. The seed
integument of Trifolium repens L. has different colors ranging from light yellow to dark brown. In
this work, the physiology of germination of light-colored, light intermediate, dark and dark
intermediate seeds was studied to highlight any difference in the percentage of seed germination
and seedling development. The results showed a lower germination rate and a noticeable reduction
of the root length in dark seeds compared to light seeds. In this context, tests to exclude a
physiological dormancy of dark seeds were performed. Light microscope and scanning electron
microscope observation were conducted to detect substantial differences in the structure and
thickness of the integument and in the quality of reserves. Biochemical investigations have
evidenced that total polyphenols content is similar in all the seeds categories, while higher amount
of total flavonoids was detected in dark seeds. Total Polyphenols and flavonoids content decreased
during germination in all seed groups
An unusual cytoplasmic component Euphorbia peplus L. endosperm
No full textThe coenocytic endosperm of Euphorbia peplus contains a complex system of flat, tightly-stacked membrane saccules which have a sinuous profile and a smooth or smooth-rough surface. They are joined by membrane-to-membrane links. The usual ergastoplasmic cisternae are an integral component of this system which can essentially be regarded as a sui generis from of endoplasmic reticulum. © 1995 Annals of Botany Company
Antheridial dehiscence in ferns
No full textWe investigated the mechanism of antheridial dehiscence in ferns for the first time using fluorescence microscopy as well as scanning and transmission electron microscopy. The mechanism leading to antheridial dehiscence in Polystichum setiferum, Asplenium trichomanes and A. onopteris was found to depend on the different cellulose contents of the inner and outer walls of the ring cells detected with calcofluor white stain and the Thie ́ry test. The extremely low cellulose content of the ring cell walls facing spermatozoids made them less mechanically resilient than external wall cells. When the ring cells absorbed water they expanded only into the antheridial cavity, pushing the gametes against the cap cell, which detached from the ring cell below and enabled spermatozoid release. The newly released spermatozoids were spherical bodies covered in cellulose fibrils. The significance of cellulose fibrils could be to isolate the gametes from each other, to reinforce the electron transparent material and to protect the gamete from pressure created by the ring cells during release
Presence, distribution and form of calcium oxalate crystals in relation to age of Actinidia deliciosa leaves and petioles.
No full textUltrastructural features of spermatocytes and spermatozoids in the fern Phillitis scolopendrium L. Newm subsp. scolopendrium
No full textPhyllitis scolopendrium Newm. subsp. scolopendrium 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
Ultrastructural features of spermatocytes and spermatozoids in the fern Phyllitis scolopendrium (L.) Newm. subsp. scolopendrium.
No full textSpermatogenesis in Phyllitis sclopendrium L. Newm. subsp. scolopendrium: the origin of the multilayered structure.
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