Giovanna Marziani

The arrest of development of abortive reproductive organs in the unisexual flower of Vitis vinifera ssp. silvestris

During the first stages of development, flowers of most dioecious species are hermaphroditic, with their transition to unisexual flowers being the result of the developmental arrest of one set of reproductive organs. In this work, we describe the development of male and female flowers of the dioecious wild grape species Vitis vinifera ssp. silvestris through scanning electron microscopy analysis and cytological observations, focusing our attention on the transition from bisexual to unisexual development. We divide floral development of the wild grape into eight stages. Differences between male and female flowers appear first at stage 6, when the style and stigma start to differentiate in female but not in male flowers. Cytological analysis of the slowly growing abortive pistil of male flowers shows that megagametophyte formation is, surprisingly, not inhibited. Instead of pistil abortion in the male flower, sexual determination is accomplished through programmed death of external nucellus cells and some layers of integumentary cells. Sterility of male structures in female flowers follows a different pattern, with microspore abnormalities evident from the time of their release from the tetrad. Sterile microspores and pollen grains in female flowers display an abnormal round shape, lacking colpi and possessing uniformly thickened cell walls that impede germination.

A genetic map of Asparagus officinalis based on integrated RFLP, RAPD and AFLP molecular markers

Abstract An integrated genetic map of the dioecious species Asparagus officinalis L. has been constructed on the basis of RFLP, RAPD, AFLP and isoenzyme markers. The segregation analysis of the polymorphic markers was carried out on the progeny of five different crosses between male and female doubled-haploid clones generated by anther culture. A total of 274 markers have been organized to ten linkage groups spanning 721.4 cM. Since the haploid chromosome number of asparagus is ten, the established linkage groups probably represent the different chromosomes; however, the only group associated with a specific chromosome is the one which includes sex, whose determinant genes have been located on chromosome 5. A total of 33 molecular markers (13 RFLPs, 18 AFLPs, 2 RAPDs and 1 isoenzyme) have been located on this chromosome. The closest marker to the sex determinant is the AFLP SV marker at 3.2 cM.

The MADS box gene AOM1 is expressed in reproductive meristems and flowers of the dioecious species Asparagus officinalis.

Abstract MADS box genes are implicated in different steps of plant development. Some of them are expressed in vegetative organs. Most of them, however, are expressed in flower tissues and are involved in different phases of flower development. Here we describe the isolation and characterization of an Asparagus officinalis MADS box gene, AOM1. The deduced AOM1 protein shows the highest degree of similarity with FBP2 of Petunia hybrida and AGL9 (SEP3), AGL2 (SEP1) and AGL4 (SEP2) of Arabidopsis thaliana. In situ hybridization analyses, however, show that the expression profile of AOM1 is different from that of these genes: AOM1 is expressed not only in flower organs but also in inflorescence and flower meristems. These data indicate a possible function of AOM1 during flower development as well as in earlier stages of the flowering process. Asparagus officinalis is a dioecious species which bears male and female flowers on different individuals. AOM1, which is expressed very early during the process of flowering and has a similar expression profile in male and female flowers, does not seems to be involved in asparagus sex differentiation.

Linkage Arrangement of RFLP loci in progenies from crosses between doubled haploid Asparagus officinalis L. clones.

A preliminary genetic map of the dioecious species Asparagus officinalis L. (2n = 20) has been constructed on the basis of restriction fragment length polymorphism (RFLP) and isozyme marker data. With DNA samples digested with either EcoRI or HindIII 61 out of 148 probes (41%) identified RFLPs in six families of doubled haploid lines obtained through anther culture. A higher level of polymorphism (65%) was observed when a single family was screened for RFLPs using six distinct restriction enzymes. Segregation analysis of the BC progenies (40–80 individuals) resulted in a 418-cM extended map comprising 43 markers: 39 RFLPs, three isozymes and one morphological (sex). These markers are clustered in 12 linkage groups and four of them exhibited significant deviations from the expected 1∶1 ratio. One isozyme and three RFLP markers were assigned to the sex chromosome.

AOM3 and AOM4: two MADS box genes expressed in reproductive structures of Asparagus officinalis

The MADS box genes participate in different steps of vegetative and reproductive plant development, including the most important phases of the reproductive process. Here we describe the isolation and characterisation of two Asparagus officinalis MADS box genes, AOM3 and AOM4. The deduced AOM3 protein shows the highest degree of similarity with ZAG3 and ZAG5 of maize, OsMADS6 of rice and AGL6 of Arabidopsis thaliana. The deduced AOM4 protein shows the highest degree of similarity with AOM1 of asparagus, the SEP proteins of Arabidopsis and the rice proteins OsMADS8, OsMADS45 and OsMADS7. The high level of identity between AOM1 and AOM4 made impossible the preparation of probes specific for one single gene, so the hybridisation signal previously described for AOM1 is probably due to the expression of both genes. The expression profile of AOM3 and AOM1/AOM4 during flower development is identical, and similar to that of the SEP genes. Asparagus genes, however, are expressed not only in flower organs, but also in the different meristem present on the apical region of the shoot during the flowering season: the apical meristem and the three lateral meristems emerging from the leaf axillary region that will give rise to flowers and lateral inflorescences during flowering season, and to phylloclades and branches during the subsequent vegetative phase. The expression of AOM3 and AOM1/AOM4 in these meristems appears to be correlated with the reproductive function of the apex as the hybridisation signal disappears when the apex switches to vegetative function.

Sull'evoluzione Dei Mitocondri Nell'endosperma di Semi di Ricino in Germinazione

Abstract On the behavior of mitochondria in the castor bean seed endosperm during the early phases of germination. — In the endosperm of the castor bean seed the oxidative activity and the protein nitrogen contents of the mitochondrial fraction markedly increase during the first period of germination (Beevers and coworkers). The activation of the mitochondrial system is paralleled by a similar increase of the activity of several soluble enzymes; the latter process is severely depressed by protein synthesis inhibitors (Cornaggia, Aberghina). The present research is aimed to understand at what extent phenomena of activation and/or, respectively, of « ex novo » synthesis are responsible of the increase of mitochondrial activity. The following aspects of the mitochondrial behavior during the early period of germination were investigated: a) Changes in the activity of cytochrome oxydase, malate dehydrogenase and of the succinate-citochrome reductase system. b) Changes in the morphology of mitochondria and othe...

A new method for cutting thin sections from prehistoric charcoal specimen

Abstract A method is described for obtaining thin sections from prehistoric charcoals, correctly oriented according to the three section planes. Charcoal pieces are embedded in epoxy resin following the method used in electron microscopy, with some modifications that are necessary because of the large size of the samples. Semi-thin sections are then obtained by means of an ultramicrotome: these can be observed under a light microscope without further processing. This method allows for obtaining comparatively large sections that can be used for wood identification.

Molecular (RAPD) analysis of some taxa of the Ophrys bertolonii aggregate(Orchidaceae)

The RAPD methodology was utilized for analyzing the genetic material of four all opatric populations of the Ophrys bertoloniiformis type, as well as of two populations of O. bertolonii s.str., together with O. fuciflora as out group. Significant gene diversity was observed for all six taxa under examination, thus suggesting their separation at specific (or sub specific) level. Comparison with other methods (biostatistical analysis and pollination biology) is also reported.

THE EFFECTS OF HUMAN IMPACT ON THE ARBOREAL VEGETATION NEAR ANCIENT IRON SMELTING SITES IN VAL GABBIA, NORTHERN ITALY

Changes in arboreal vegetation near ancient iron smelting sites in Val Gabbia, a lateral valley of Val Camonica, Brescia, northern Italy, were studied using charcoal analysis at three archaeological sites. The charcoal samples analysed derive from charcoal stores and furnaces used for iron ore smelting during different periods spanning the interval A.D. 500 to 1700. As a reliable description of the woodland cover in the valley during this period does not exist, charcoal analysis is a useful approach for studying the effect of human impact on a forest exploited for the iron industry. Our results indicate that the conifer forest, consisting ofAbies alha, Picea abies and/orLarix decidua, which was present in the early stages was replaced after 600 years by a mixed forest and, 300 years later, by a degraded forest dominated byOstrya carpinifolia, a typical pioneer species. The youngest period is characterised by the reconstitution of a mixed forest with coniferous and deciduous trees.

Ricerche Sulla Morfogenesi Dei Plastidi Clorofilliani

Abstract Studies on chloroplast morphogenesis. The effect of sucrose feeding and light intensity on the plastids of etiolated plants. — The changes in the fine structure of the plastids of etiolated Bean plants, dipped into water or in various sucrose concentrations, for 24, or more, hours, and exposed to conditions of darkness and weak light, were studied at the electron microscope, and protochlorophyll, chlorophyll a and chlorophyll b contents were determined. When the etiolated plants are dipped into water or sucrose solutions, in the dark, rows of tubules and lamellae, often stacked and resembling small grana, are formed in the plastids. These structural changes of plastids of the plants exposed to conditions of darkness, where no protochlorophyll was converted to chlorophyll a, are quite similar to those described by several Authors for plants exposed to light conditions and thought to coincide with the protochlorophyll-chlorophyll transformation. Thus, the preservation of the « Kristallgitterstruktu...