Inventaire des algues et phanérogames marines benthiques de la Tunisie

Abstract

Check list of the benthic marine flora of Tunisia. — 393 species, varieties, formae and stadii of algae and seagrasses are listed: 6 Bangiophyceae, 239 Florideophyceae, 1 Xanthophyceae, 82 Phaeophyceae, 20 Chlorophyceae, 45 Bryopsidophyceae and 5 seagrasses.     

Ricerche Sull'ultrastruttura dei Tubi Cribrosi di Piccioli di Foglie di Edera

Abstract

The ultrastructure of sieve tubes in leaf petioles of HEDERA HELIX. — The structural organization of the sieve elements in Hedera leaf petiole at the beginning of the second year of life has been studied. At this stage of life the sieve tubes are completely developed, but still in full activity.

Their plasmatic structures, though altered, show that they are still alive. The cytoplasm forms a parietal layer; mitochondria, endoplasmic reticulum and plastids are present although very peculiar in aspect. The cytoplasm is bounded externally by a plasmalemma; on the contrary no tonoplast is detectable.

The data reported in this paper are favourable to the idea of an active partecipation of the sieve tubes in the translocation of organic solutes, in agreement with the findings concerning the oat coleoptile.     

The coastal fringe: Habitats threatened through global warming

Summary

Vegetation of the coastal fringe of Scotland (sea cliffs, dunes and salt marshes out to the depth limit of benthic algae and seagrasses) was subject to repeated cycles of glaciation, with low values of temperature, sea level and atmospheric CO₂, alternating with interglacials with higher temperature, sea level and atmospheric CO₂. The glaciations occasioned migrations of hundreds of kilometres south, and tens of metres downshore, to appropriate temperatures and zones on the shore. Losses of species from Scotland's coastal fringe flora as a result of these assaults are poorly documented, and direct evidence from fossils is lacking for seaweeds; more certainly, the present native coastal fringe flora must have managed to survive the last glacial-interglacial cycle although presumably not in Scotland. This does not necessarily mean that the coastal fringe species can withstand the current anthropogenic greenhouse effect (global warming) in which CO₂ partial pressure started to increase in about 1800, with subsequent increases in temperature and sea level, since the upper limits of the excursions of these three environmental factors during the last glacial- interglacial cycle may soon be exceeded. Furthermore, the rate of increase of these factors may be greater than that found in the glacial-interglacial transitions. Coastal fringe vegetation may also be threatened by more local anthropogenic actions, e.g. physical modification of the habitat by coastal defences against sea level increase, inputs of chemical pollutants, and direct harvesting of native plants or introduction of exotics. It is clear that, when the perturbation is removed, the vegetation can be substantially restored at least under present environmental conditions. Scottish botanists, while not able unaided to influence the global threats, can and should take action to minimize local anthropogenic threats, and monitor, and respond flexibly to, the response of the vegetation to the global and local changes.     

Analisi informazionale degli schemi di dinamica della vegetazione. Un esempio sul popolamento vegetale delle dune del litorale di Venezia

Abstract

A method to quantify the dynamic schemes of vegetation based on information functions.—The dynamic schemes of vegetation as proposed by Braun-Blanquet have been never quantified with the aim to give indirect measures of the probability of transition between the types. This work presents a method that quantifies the arrows between the types by means of a redundancy measure. This is calculated by comparing the phytosociological types two by two. Redundancy, as proposed here, measures the similarity between the tables not only based on species composition but also on the basis of species cooccurrence. The method relies on the assumption that in a succession the higher is the redundancy between the types, that are presumably in sequence, the higher is the probability and then the velocity of transition from one type to another one. An example is given with data from coastal dune grasslands of the Venice Lagoon.     

Fenomeni di Inattivazione e di Riattivazione Enzimatica in Endospermi di semi di Ricino

Abstract

Inactivation and riactivation of enzymes in endosperms of castor bean seeds. — On the basis of previous results, the possibility has been investigated of the reversible interconversion of active and inactive form of enzymes in castor bean seeds, during their development.

The results described here indicate that:

1. the activity of some glycolytic enzymes increases greatly (81% and 400% increase of, respectively, Gl-6-P-dehydrogenase and aldolase) upon incubation of dry seeds for few hours at 4 °C.

2. The decrease of enzyme activity upon dehydration of seeds and the increase during the subsequent imbibition can be shown reproducibly.

3. This same observation is made for oxygen uptake.

These results are interpreted to indicate the reversible inactivation of enzymes caused by dehydration of seeds.     

Fissazione di CO2 da Parte di Entomocecidi di Cuscuta Australis

Abstract

Fixation of carbon dioxide by galls of CUSCUTA AUSTRALIS. — The mechanism of the carbon dioxide fixation by Cuscuta is a controversial biochemical topic. Light induced reactions are involved in MacLeod's opinion while others as Ciferri and Poma believe that mainly a dark-fixation occurs.

In this study use is made of the galls, caused by the insect Smicronyx on Cuscuta australis, that appear more green coloured than the normal tissues.

Equal weights of excised galls were kept both in light and in darkness in contact with C¹⁴O₂for different incubation times, and the magnitude of the fixation was compared under these two conditions by measuring radioactivity of both soluble and acid hydrolysed fractions.

After short exposures to the tracer the fixation in light greatly exceeds that in dark (25–19/1) while with more prolonged exposures the ratio sharply decreases (to about 5/1): these figures can be interpreted with the assumption that a strong light-induced fixation superimposes itself to a low but definite dark-fixation activity.

The ratio does not change if radioactivity is measured in the hydrolysed fractions.

These results are of course referred to as being largerly preliminar and requiring further and more extensive studies.     

Demographic and genetic connectivity: the role and consequences of reproduction,dispersal and recruitment in seagrasses

Accurate estimation of connectivity among populations is fundamental for determining the drivers of population resilience, genetic diversity, adaptation and speciation. However the separation and quantification of contemporary versus historical connectivity remains a major challenge. This review focuses on marine angiosperms, seagrasses, that are fundamental to the health and productivity of temperate and tropical coastal marine environments globally. Our objective is to understand better the role of sexual reproduction and recruitment in influencing demographic and genetic connectivity among seagrass populations through an integrated multidisciplinary assessment of our present ecological, genetic, and demographic understanding, with hydrodynamic modelling of transport. We investigate (i) the demographic consequences of sexual reproduction, dispersal and recruitment in seagrasses, (ii) contemporary transport of seagrass pollen, fruits and seed, and vegetative fragments with a focus on hydrodynamic and particle transport models, and (iii) contemporary genetic connectivity among seagrass meadows as inferred through the application of genetic markers. New approaches are reviewed, followed by a summary outlining future directions for research: integrating seascape genetic approaches; incorporating hydrodynamic modelling for dispersal of pollen, seeds and vegetative fragments; integrating studies across broader geographic ranges; and incorporating non‐equilibrium modelling. These approaches will lead to a more integrated understanding of the role of contemporary dispersal and recruitment in the persistence and evolution of seagrasses.     

Vegetazione e ambiente delle Marche e relativi problemi di salvaguardia

Abstract

Vegetation and environment in the Marche and related problems of protection. – The « Marche » region is situated in central Italy and corresponds with the natural region east of the Appennine ridge and spreading as far as the coast which is washed by the Adriatic Sea.

As to the climate, we may distinguish a coastal strip with Mesomediterranean climate with dry season, corresponding to the distribution area of Quercus ilex; a hilly strip with Submediterranean climate, corresponding to the distribution area of Quercus pubescens; a mountain strip with temperate axeric climate with sub-dry period, corresponding to the distribution area of Fagus silvatica and finally a high mountain strip with cold axeric climate, corresponding to altitude pastures. The Marche vegetation is shown in the vegetation map of Fabriano sheet (scale 1:50,000) plotted according Ozenda's vegetational series.

The following vegetation series have been plotted: submediterranean series of Quercus ilex; series of thermophilic oak wood with priority of Quercus pubescens or Quercus cerris; series of Ostrya carpinifolia; series of Quercus petraea and series of Fagus silvatica.

As far as the problems to safegard environment are concerned, a plan is given providing for the institution of 4 complete nature reserves, 34 nature reserves, and 9 regional nature parks among which those of Monte Conero, of Monti Sibillini and Monti della Laga.     

Benthic marine flora in the Tuscan Archipelago. A first contribution: Isles of Capraia,Elba, Formiche di Grosseto,Giglio, Scoglio d'Africa,Montecristo and Giannutri

Abstract

Benthic marine flora of Tuscan Archipelago has been studied. Several samples were collected along five islands and some rocks. This paper is a compendium of new and already published data, in which 267 species, varieties, forms and stadia of algae and seagrasses are listed: 5 Bangiophyceae, 182 Florideophyceae, 45 Phaeophyceae, 6 Chlorophyceae, 28 Bryopsidophyceae, 1 Angiospermae.     

Tecniche di Coltura di Semi di Grano Sottoposti ad Operazioni di Trapianto Embrionale

Abstract

Cultural techniques for wheat seeds submitted to embryo transplantation. — The author, on the basis of his experience coming from the work carried out on the embryo transplantation for several years, takes in consideration some aspects, at technical level, regarding the best way to cultivate wheat seeds submitted to embryo transplantation operations.

In particular, the author refers on the possibility to sow the transplants just made (while the traditional method foresees the drying of transplants for 48–96 hours under laboratory conditions) and he illustrates the results of the transplant culture in jiffypots, which allow to improve survival of materials intended for the growth in field.     

Processi di Neoformazione di Mitocondri Nella Cellula Vegetale

Abstract

Processes of formation of new mitochondria in plant cells. — While studying with the electron microscope the quiescent centre in the onion (Allium cepa) root tips, the writer was able to observe the endoplasmic reticulum arranged into peculiar concentric ring systems, which are here described. In some of the ring structures, between a ring and the contigous one, mitochondria-like bodies are formed, which are then detached by a kind of budding process. A short review of the current literature on formation of the mitochondria is also reported.     

Effetto Dell'attinomicina Sulla Crescita di Alcune Specie di Alghe

Abstract

Action of Actinomycin on the growth of Algae. — Actinomycin C inhibits the growth of two strains of Euglena gracilis, of Chlorella vulgaris, of Prototheca zopfii and of Scenedesmus sp. The growth inhibitory effect is evident on both autotrophically and heterotrophically grown cultures. DNA extracted from C. vulgaris appears to form a complex with Actinomycin C similar to that observed in the case of other organisms.     

Effetto di Popolazione tra Espianti di Helianthus Tuberosus

Abstract

Population effect among explants of jerusalem artichoke. — We found that among explants of Jerusalem artichoke cultured « in vitro » are not present positive population effects, as reported by others A.A.     

Assunzione di Fosforo32 da Parte di Cuscuta Epithymum Parassita di Trifolium Repens

Abstract

Uptake of Phosporus-P³² by CUSCUTA EPITHYMUM parasitic of TRIFOLIUM REPENS. — Filaments of C. epithymum, parasitic on T. repens, partially immersed in a solution containing KH₂P³²O₄, uptake from the host solely, or mainly, radioactive ortophosphate. Radioactive hexose phosphates and radioactive nucleotides present in the extracts prepared from C. epithymum, appear to be the result of the metabolization by the dodder of the orthophosphate uptaken from the host.     

Ricerche Comparate Sulla Morfologia e Sulla Fisiologia di Larix e di Picea

Abstract

Comparative researches on morphology and physiology of PICEA and LARIX. The chlorophyll content of seeds and seedlings during germinations in darkness. — Very different are the chlorophyll contents of the seeds and the seedlings of Picea excelsa and Larix decidua grown in darkness.

In Picea chlorophyll is abundantly synthetized in cotyledons in the passage from seed to seedling stages. In Larix however this synthesis is very poor. These differences are more evident after the outgrowth of cotyledons from the primary endosperm and its exhaustion.

If seedlings of both species are exposed to 3.000 lux of light intensity for 24 hours, after development in darkness, one can observe much stronger chlorophyll synthesis in Larix cotyledons than icea.

These figures quanti atively express the different light-dipendence of chlorophyll synthesis in these two plants and offer a more adherent interpretation of the different ecological behaviours that are caracteristic of these two plants.     

Ricerche Sulla Cultura Sommersa di Cellule Singole di Piante Superiori

Abstract

Research on submerged culture of single cells of higher plants. — The author describes a method which allows to obtain submerged cultures of single cells of Phaseolus vulgaris and Nicotiana tabacum. The medium composition in macroelements in the culture on agar appears to effect to a great extent the ability of tissues to dissociate into single cells in the subsequent liquid culture. In this respect Heller's solution results to be more suitable than Gautheret's and Hildebrandt and Ri-ker's.

Cells are grown at 24 [ddot]C in 300 ml flasks containing 60 ml of broth on a rotary shaker at 220 rpm.

To prevent contaminations some antibacterial agents were added to cultures of Phaseolus vulgaris. Among these Penicillin and Neomycin were not tossic at 20 and 5 ppm concentrations respectively.

The presence of septa, which are observed also in largely vacuolate cells, seems to confirm the ability of single cells to divide.

The optimum 2,4-D concentration for growth decreases from 6 × 10^-8 to 6 × 10^-8 during successive liquid cultures, each of them being inoculated with on amount of the previous one. This fact, showing the adaptation of liquid cultures to decreasing concentrations of the growth hormone, is in agreement with previous observations in solid cultures by several authors.     

Residui di Leccete pure e miste sulla Murgia di Putignano

Summary

Purpose of this paper is to point out the residues of Quercus Ilex woods in the hilly region of Murgia di Putignano (Puglia) which lies inside the distribution area of Q. trojana, now the main wood-forming tree-species of this territory.

Fourteen different small Q. Ilex stands are mentioned, as marked on alleged map. One of them (n° 1 on the map) has been more carefully studied through a whole year, and all plants growing in it have been collected.     

Microtuboli in Cellule Parenchimatiche ed Epidermiche di Coleottile di Avena

Abstract

Microtubules in parenchyma and epidermis cells of avena coleoptile. — The fine structure of differentiating parenchyma and epidermis cells of the oat coleoptile, fixed in glutaraldehyde-osmium tetroxide, or glutaraldehyde-potassium permanganate, was investigated. Tubular structures have been observed aligned in the peripheral cytoplasm, between the cell wall and the plasma membrane, embedded in the cell wall and inside the tonoplast in the vacuoles.

The nature and function of these structures are yet unknown. Microtubular structures, localized beneath and above the plasma membrane, have been associated to the wall development; the function of the microtubules observed in vacuoles results, anyhow, of far problematic interpretation.     

Resoconto di Una Erborizzazione Nell'Isola di Giannutri (Arcipelago Toscano)

Abstract

A botanical trip at Giannutri (Tuscan Islands). — The Author refers on an excursion of 10 years ago, listing all the plants known up to day for Giannutri. A brief geobotanic picture of the place is given and some protective measures are claimed.