Maria Grilli Caiola

LYSIS OF MICROCYSTIS AERUGINOSA (KÜTZ.) BY BDELLOVIBRIO‐LIKE BACTERIA1

Cells of Microcystis aeruginosa (Kützing), collected from water‐blooms of Lake Varese, were lysed by Bdellovibrio‐like bacteria. The cells were lysed only after penetration. The cyanobacteria and lysing bacteria were characterized by a fibrous glycocalyx. Once the host cell was penetrated, the bacteria remained localized mainly between the host cell wall and cytoplasmic membrane, which appeared partially thickened. Cell lysis began by breakdown of cell structures. The cell wall appeared broken at many sites, and in completely lysed cells, was partially interrupted. The lysis of Microcystis by bacteria could be one of the causes of the death of algal blooms.

A light and electron microscopic study of the blue-green algae living either in the coralloid roots of « Macrozamia communis » or isolated in culture

Abstract The present work is a study of the blue-green algae living in the coralloid roots of Macrozamia communis and isolated from Macrozamia communis in culture. The light and electron microscopic study pointed out the distribution of these microorganisms in the cortical area of coralloids and did not reveal any cells invaded by bacteria. On the basis of their aspect the blue-green algae living either in the coralloid roots or in culture were classified as belonging to the genus Nosloc, with some features of Nosloc commune. Inside the coralloids the cells of the blue-green algae were surrounded by abundant mucilage and contain granulations. In culture the blue-green algae were on the contrary very poor in mucilage and rich in polyphosphate granules. Numerous phycobilosomes were ranged along the outside of the thylakoid membranes in alternate arrangement to the granules of the neighbouring lamellae.

Cell Morphology of the Blue-Green Algae Under Culture Conditions from Cycas Revoluta Isolated. I: Light Microscope Observations

SUMMARYColonies of blue-green algae isolated from root nodules of Cycas revoluta were grown on artificial media in order to study the effects of light (room conditions or continuous light) on culture morphogenesis.All the observations were carried out under the light microscope on fresh or stained material. Three main types of cells were observed: vegetative cells, heterocysts and akinetes. Colonies kept under room light grew more slowly, were darker green, had a larger number of vegetative cells in the youngest cultures and a larger number of akinetes in the older ones. The colony filaments presented a linear pattern. In the vegetative cells several granule types were recognizable, which, on the basis of the histochemical reactions used, could be identified respectively as polyphosphate, cyanophycin and lipidie granules. In the heterocysts and in the akinetes they were abundant.The colonies grown under continuous light conditions grew faster and their pigmentation was at first green, then yellow. In the ...

Ultrastructural study of Saffron pollen

Abstract Pollen of Saffron (Crocus sativus L.), a sterile autotriploid plant was studied using scanning and transmission electron microscopy. The pollen of mature anthers had grains not containing pores or furrows, a discontinuous thin exine and a very thick intine crossed by tubules containing granular electron-dense material. Electron transparent material and lipid bodies were abundant in the cytoplasm which also contained a large number of vesicles. A high percentage of pollen grains showed anomalies.

Cell Morphology of the Blue-Green Algae Under Culture Conditions from Cycas Revoluta Isolated. II: An Electron Microscope Study

SUMMARYColonies of the blue-green alga isolated from root nodules Cycas revoluta were grown under different light conditions. The cell features as observed in the electron microscope, are here reported.The vegetative cells, the heterocysts and the akinetes were observed. The photosynthetic apparatus of the vegetative cells of the cultures grown under room light conditions appeared of the reticular type, with structured, polyhedral, poliglucoside and polyphosphate granules, lipid globules and some particular « gamma » granules; the last ones were roundish, very electron opaque and prevalently localized in the centroplasm. These granules were evident after KMnO4 fixation.The vegetative cells of the colonies grown under continuous light showed an early generalized process of vacuolisation and keritomie and contained polyglucoside and structured granules, lipid globules and cavities delimited by a fine dark membrane. Several of these bodies contained a granular substance (vacuolar granules), and were interpre...

Seed structure in Crocus sativus L. ×, C. cartwrightianus Herb., C. thomasii Ten., and C. hadriaticus Herb. at SEM

Crocus sativus L. (Iridaceae) is a sterile triploid geophyte widely cultivated for the production of the spice saffron and only reproduced by means of corms. Extensive research has identified Crocus cartwrightianus Herb. as being a probable progenitor of C. sativus. However, other diploid Crocus species of the same C. sativus group, such as C. thomasii Ten. and C. hadriaticus Herb., have been considered as possible progenitors of saffron. Of the characteristics for distinguishing critical genera, species and intraspecific taxa of angiosperms, the most widely adopted have been seed organisation and patterns of spermoderma microstructure detected at SEM. The aim of this study is to use SEM to analyse the seeds of C. sativus ×, a cross obtained by C. sativus with pollen of C. cartwrightianus Herb. and the seeds of allopollinated C. cartwrightianus, C. thomasii Ten., and C. hadriaticus Herb. Results indicate that the seed surface microstructure of C. sativus × is very similar to that of C. cartwrightianus while being different from those of C. thomasii and C. hadriaticus.

Hermodactylus tuberosus L. (Iridaceae) pollen organisation before and after anther dehiscence

ABSTRACT The morphology, cytology and viability of Hermodactylus tuberosus L. (Iridaceae) pollen were examined from the first mitosis until maturation and after anther opening. During maturation, the pollen coat becomes modified, and the vegetative cell cytoplasm accumulates several types of reserve substances. In the vegetative cell cytoplasm, starch is quickly utilised whereas lipid inclusions of different dimensions, shape and composition occur during pollen maturation. Pollen from opened anthers have a thin pollen coat; the cytoplasm has mostly lipid reserves, and many small vesicles and vacuoles. It is similar in size or larger than pollen located inside the anther, and its viability does not decrease until one day after anther dehiscence. Large osmiophilic bodies, different from those of the vegetative cell cytoplasm, are present in the generative cell cytoplasm starting from the first stage of pollen development. The poorly developed pollen coat in pollen from opened anthers suggests that it plays a minor role in attracting insects for pollination. The size and structural and ultrastructural features of mature pollen indicate that it does not undergo dehydration and possesses sufficient vigour for immediate germination.

Palynological study of Cupressus sempervirens L. var. pyramidalis and var. horizontalis

ABSTRACT Cupressus sempervirens L. var. pyramidalis and C. sempervirens var. horizontalis were examined for their pollen morphometry and ultrastructure to verify whether, in addition to phenotype, pollen could also show characteristics useful to discriminate the two infraspecific taxa. C. sempervirens var. pyramidalis compared to C. sempervirens var. horizontalis has mainly larger, subcircular pollen with a higher percentage of apolar and germinating grains, and a wall with thicker intine; the cytoplasm has a greater number of callose-containing vesicles. C. sempervirens var. horizontalis has pollen distributed in five classes of shape. In addition it is smaller and shows a higher percentage of ruptured grains, and a lower percentage of germination in vitro. The cytoplasm contains vesicles rich in callose and also a higher amount of osmophilic bodies. Pollen grains in both varietas contain only one cell at dispersal. The reported differences in pollen morphometry, structure and biology, together with the phenotypic characteristics of the tree, support the validity of two infraspecific taxa.

The Effects of Various Light Intensities on Nostoc Punctiforme (Kützing)

SUMMARYWe studied by light and electron microscopy the influence of different intensities and periods of illumination on the life cycle and morphogenesis of Nostoc punctiforme (Kutz.) grown in nitrogen-free medium. By using light intensities between 500 and 2800 lux it was observed that the developmental cycle of N. punctiforme consists of a complete heterocystous phase and o a truncated sporogenous phase. The first phase is characterized by aseriate, spherical, or elongated colonies formed by a filament of vegetative cells and heterocysts. The filament is always enveloped in a watery or firm sheath which forms a surface pellicle. The sporogenous phase stops with the formation of coccoid cells formed along the filament of aseriate colonies. The coccoid cell may be released or remain in the mother colonies where they germinate originating directly new aseriate colonies. The nature and functions of such particular cells, which are considered immature spores are discussed.The various light intensities influe...

Effects of Various Nitrogen Sources on Nostoc Punctiforme (Kützing)

SUMMARYThe modifications which accompany the growth of Nostoc punctiforme in culture media containing various forms of mineral nitrogen were described by light and electron microscopy. The presence of 0.012M NaN03 and 0.04M NH4Cl inhibit heterocyst formation, while lower doses reduce their frequency. Parallel to the disappearance of heterocysts is the disappearance of the aseriate stage, so that the whole culture is made by long filaments formed by vegetative cells and, in particular conditions, by cells similar necridia and discs. When grown in presence of nitrogen compounds, the vegetative cells contain numerous and large cyanophycin granules. The higher large amounts of nitrates induce the formation of particular vegetative cells deprived of cyanophycin and enveloped in abundant mucilage. Some of these particular cells are similar to analogous found in the gonidial zone of coralloid roots of Cycads. The absence of true spores in the different culture media is discussed.