1,721,003 research outputs found
Effects of copper on spore germination, growth and ultrastructure of Polypodium cambricum L. gametophytes
No full textThe effects of different concentrations (10-5, 5 x 10-5 and 10-4 M) of copper bromide on spore germination, growth and ultrastructure were investigated in Polypodium cambricum L. gametophytes. The inhibitory effect of Cu was observed in spores cultured on medium supplemented with 10-4 M CuBr2: germination occurred about 40 days after sowing and was only 25%. Concentrations of 5 x 10-5 and 10-4 M CuBr2 induced changes in gametophyte development, possibly by re-orientation of growth. Gametophytes treated with 10-5 and 5x 10-5 M CuBr2 took up and accumulated a large amount of copper and ultrastructural observations showed that cytoplasmic damage was limited to twisted swollen thylakoids. The ultrastructure of gametophytes treated with 10-4 M CuBr2 showed absence of a vacuolar compartment. The present observations suggest that P. cambricum gametophytes could be a suitable material for studying physiological and molecular alterations induced by excess copper
Ultrastructure of mature spermatozoids in the fern Asplenium onopteris L.
No full textAsplenium onopteris L. spermatozoids are 8–8.5 mm long in the form of spirals with 4.5 turns. They have about 50 flagella. The nucleus occupies the last three posterior turns. Chromatin is partly honeycomb-shaped and partly highly condensed. An electron transparent space crossed by dense fibers delimits the condensed chromatin. Here, the nuclear membranes are closely apposed without any space between them and the plasmalemma often invaginates among elements of the microtubular ribbon, connecting with the outer nuclear membrane. An electron opaque body apparently links and anchors all anterior spermatozoid components. The cytoplasm contains plastids with starch grains,
(lipid) bodies and different membrane systems, which are presumably plasmalemma derivatives involved in a process of cytoplasmic reduction
Biologia della riproduzione di Asplenium trichomanes ssp. trichomanes. 1. Anteridi e spermatociti.
No full textBiologia della riproduzione di Asplenium trichomanes ssp. trichomanes. 2. Caratteristiche ultrastrutturali dello spermatozoide
No full textULTRASTRUTTURA DELLE CELLULE DEL GAMETOFITO DI POLYSTICHUM SETIFERUM (FORSSK) T. EX WOYNAR'
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NUCLEAR PARACRYSTALS IN THE FERN POLYSTICHUM SETIFERUM GAMETOPHYTE
No full textSingle nuclear paracrystals were observed in gametophyte cells of the fern Polystichum setiferum. They consist of proteins poor in basic aminoacids and have sharp-profiled, polyhedral shapes, with inner diameters up to 4.5 mu 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
Ultrastructure, viability, and in vitro germination of the tricellular Sambucus nigra L. pollen
No full textMature pollen grains of Sambucus nigra L. are tricolporate, isopolar, 12.5 mm wide, 25 mm 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 20C 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
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