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.     

Ricerche Sulla Vegetazione dei Dintorni di Firenze

Summary

It is related on some phytocenoses of the southerly Florence hills, lying on the boundary of the two basal biochores of peninsular vegetation. Although the proximity and the chorographical analogy at the south-westerly ones and at Ceceri Mount, which are included yet in the » Quercetum Ilicis « ambit, these hills are whereas sensible displaced in the » Quercetum pubescentis «. They have microtherme elements of higher planes, but they have in yet the marks of littoral biochore, for instance Smilax aspera, abundantly penetrating in hedges and in a pine-grove but non in coppices of Quercus Cerris.     

Ricerche Sulla Vegetazione dei Dintorni di Firenze

Riassunto

L'A. espone in questo lavoro i risultati di ricerche sistematiche e fitogeografiche sulla vegetazione di Monte Ferrato (presso Prato in Toscana), piccolo gruppo di colline costituite da rocce ofiolitiche (serpentino, eufotide ecc.), Dopo averne elencata la florula, dove riporta anche le diagnosi di alcune forme nuove, l'A. prende in esame la vegetazione dei principali tipi di stazione, che vi ha potuto riconoscere, in base a criteri fisionomici e statistici. Considera poi le caratteristiche morfologiche delle specie pi[ugrave] significative del serpentino, che raggruppa in cinque tipi di speciali morfosi. Sulla base dell'analisi della distribuzione geografica di alcune notevoli entità che si presentano a M. Ferrato in stazione disgiunta rispetto al loro areale, dello studio geografico e sistematico degli endemismi, e in genere poi di tutte le specie pi[ugrave] significative di questa Flora, l'A. ne discute il valore fitogeografico e climatico, rilevando e discutendo la convivenza di specie di diverso valore fitogeografico, in rapporta alle particolari condizioni microstazionali.     

Caratteristiche della fosfo-gluco-isomerasi di una pianta superiore

Abstract

PHOSPHOGLUCOISOMERASE FROM PEA COTYLEDONS. — 6-P-glucose iso-merase has been purified from pea cotyledons. A 70-fold purification has been obtained by means of acetone fractionation and two absorption-elution steps on calcium phosphate gel. The partially purified enzyme is free of interfering activities.

KM values of 2.5×10^?4 and 10^?4 been measured for glucose-6-P and fructose-6-P respectively. reaction, measured at pH 7.8 and 30° C., is 3.7 (Gl-6-PIFr-6-P).

The enzyme is not inhibited by p-chloro-mercurybenzoate up to 10^?3 M. Besides the substances already known to inhibit competitively the isomerase from animal tissues, the pea enzyme has been found to be competitively inhibited by ribose-5-P and by triosespho-sphates, the K₁, being respectively 7×10^?4 and 2.5×10^?4.

The properties of the pea enzyme are compared to those of animal tissues isomerase. The possible physiological significance of these properties is discussed.     

Determinazioine di frammenti di legno provenienti da una casa romana di Scedena (Tripoli)

Summary

The Author describes two samples of subfossil woods, digged out from a roman house at Scedena, near Tripoli, and identifies them as Tamarix cfr. africana Poiret.     

Influenza a distanza dei metalli sopra lo sviluppo di organismi vegetali inferiori

Summary

The Author relates about two new spontaneous stations of «Salvia Sclarea» in Sardinia, one of them is probably a shelter-station of another one pre-existing in a lower zone being about 200 meters from it. He refers about the actual area of the species; he describes the two stations and their relative plant-communities pointing out the indexes of plentifulness of the consociated species and comparing the biological spectra of them.

Wishing to research the reason why the species is so restive to spread spontaneously, while it is easily fitted for cultivation, the Author carries on a compared chemical-pedological study of the two stations with three other spontaneous stations near Sassari. He concludes that the «Salvia Sclarea» in sub-alkaline ground does not present particular exigences of chemical constitution, while it would meet difficulties to spread spontaneously in not very soft ground.

As the mentioned difficulties depend from particular conditions of aeration, temperature and humidity of the ground, the Author reserves to himself to make a further research in his next study.     

Osservazioni Preliminari Sulla Struttura Submicroscopica dei Granuli di Amido dell'endosperma Maturo di Triticum Durum Desf

Abstract

Preliminary observations on the submicroscopic structure of the endospermic starch granules in TRITICUM DURUM desf. (The electronic transparency of the starch granules). — The starch granules of Triticum durum Desf. kernels have been examined by electron microscopy.

The high degree of transparency of the granules appears to depend upon the regular disposition of the structural units, while their opacity probably is in relation with their orderless arrangement. The opacity of amorphous portions of the layers, of the median fissure and of the black bands seems to be in relation with the amorphous condition of such formations.

The black bands and the bubbles which have been considered respectively as protein layers and as the result of enzymes action, are only artifacts. The bubbles are interpreted as pyrodestrines.     

Evoluzione Biochimica Delle Sostanze Nutritive di Riserva dei Semi di Triticum Ramosum Albo. Riassunto

Abstract

Biochemical evolution of the reserve nutrients in TRITICUM RAMOSUM albo seeds. — The author refers on his further experiments of cultivation of Triticum ramosum typicum and Triticum ramosum hyblaeum, and of chemical analisis of reserve nutrients of the seeds.     

Aspetti Enzimatici Della Maturazione e Germinazione dei Semi di Ricino

Abstract

Enzyme levels during ripening and germination of castor bean seeds. — During the development of the endosperm of castor bean seeds two distinct phases can be recognized: pre-maturation and germination. The former is characterized, metabolically, by the rapid conversion of carbohydrates into lipids, and storage proteins. The latter is characterized by the reconversion of these storage materials into sugars. Both these processes are dependent upon the activity of the glycolytic pathway; for this reason the behaviour of some enzymes of this pathway and, in general, of the carbohydrate metabolism have been studied during the two phases. The changes (during the evolution of the seeds) of the following enzymes have been studied:

Gl-6-P-dehydrogenase, 6-P-gluconate dehydrogenase, P-glucomutase, Hexokinase Hexoseisomerase, Aldolase, alcaline and acid Phosphatase, Pyrophosphatase and ATP-ase.

All these activities have been measured in the 20.000 × g supernatant fraction of cell homogenates.

The results show that all the enzymes activities measured increase rapidly during the period of accumulation of storage materials. In the following period all of these activities decrease until the stage of ripeness of the seed. During the first few days of germination the activities increase again rapidly. A particular behaviour is the one of Fr-1-6-P-phosphatase (the enzyme cleaving the phosphate bond in C ¹ position). This enzyme reaches during germination a level much higher than the maximal observed during the ripening process. This might be an important fact correlated with the inversion of the glycolytic reactions during germination.     

Inattivazione dei Mitocondri Negli Endospermi di Ricino Durante la Maturazione

Abstract

inactivation of mitochondria in the castor bean seed endosperm during ripening. — The present research deals with the behaviour of mitochondria from the endosperm of castor bean seeds, during the last phases of seed maturation. The activities of citochrome oxidase, of malate dehydrogenase, of the succinate-citochrome c reductase system, and the phosphorylating activity, were chosen as tests of the state of mitochondria.

The results obtained show an increase of the first two activities up to the moment when some ovular tissues are still present, and, successively, a more or less rapid inactivation of the three enzymes investigated, which fall to extremely low values in the dry seed. Also the phosphorylating capacity, high during the first phases, drops quickly as the seed approches to dormancy.

A certain amount of citochrome oxidase is revealed in the supernatant from 20000xg centrifugation made to prepare the mitochondrial fraction; its activity gradually increases as the seed advances to ripeness. A further fractionation of the activity not sedimenting at 20000xg reveals that approximately one half of it sediments when centrifugated for 1 hour at 50000xg, while the other half remains in the supernatant. The particles sedimenting between 20000 and 50000xg show very little, if any, phosphorylating capacity (with succinate).

It is suggested that the gradual inactivation of mitochondrial efficiency during the ripening phase is due to a degradation of mithochondrial structures.