La Distribuzione e La Funzionalita Dell'Acqua Nella Cellula Vegetale

Riassunto

L'A. studia le modalità della perdita di acqua delle. cellule vegetali in via di essiccamento. In questa ricerca di fisiologia cellulare, condotta per via sperimentale e per esame citologic, I'A. dimostra come la perdita di acqua si verifichi nella cellula in stadi distinti corrispondenti alla distini corrispondenti alla disidratazione dei singoli organiti della cellula e alle diverse forme nelle quali l'acqua si trova presente nella cellula stessa. Una parte principalissima ha, in questa disidratazione, il muco-proteide, il nuovo costituente fondamentale del protoplama recentemente scoperto e illustrato dall'A. Egli dimonstra come le differenti fasi di smescolamento pi[ugrave] o meno avanzato, in cui si può presentare il mucro-proteide, regolino non solo la perdita d'acqua nell'essiccamento sperimentale, ma regolino altresi tutta l'economia dell'acqua e della soluzioni della pianta vivente, specialmente in quelle sottoposte a regime di xerofilia.     

Saggi Sul Comportamento Della Cellula Vegetale di Fronte al Reattivo di Schiff

Riassunto

Sono state fatte diverse prove per la reazione di Schiff, di Feulgen e di Bauer su tessuti vegetali. Diversi tipi di membrane, fra cui quelle lignificate, sono risultati Schiff positivi. I nuclei sono risultati Feulgen positivi, con l'eccezione dei nuclei del gametofito maturo di Crinum sp., i quali sono tutti Feulgen negativi, meno quelli antipodali. L'amido e tutte le membrane sono risultati Bauer positivi.     

Studio di Sostanze Anticrescita di Origine Vegetale

Abstract

Antigrowth substances of plant origin. 1) A method for quantitative evaluation of antigrowth activity. The antigrowth activity of various kinds of plant extracts has been quantitatively evaluated, by determining the reduction of lenghtening of the lateral radicles of wheat grains induced by them. Grains are allowed to develop on water moistened filter paper until the lateral radicles have reached a lenght of about 5 mm.; then grains, carefully selected for approximately equal redicles lenght, are uniformly distributed in Petri dishes lined with filter paper, and moistened with 10 ml of distilled water, for the controls, or of the extracts under examination. All the operations are performed as much as possible under steril conditions. After 36 hrs incubation at 28° C, in the dark, the lenght of the lateral radicles is measured and the percent inhibition determined. This, when plotted against the log of the extract concentration, gives a straight line. The method is very sensitive and its reproducibility makes it possible to follow quantitatively the purification of antigrowth principles.     

Ricerche Sui Fenomeni di Contrazione di Mitocondri Isolati di Internodio di Pisello

Abstract

Study on the contraction phenomena of isolated mitochondria of pea internodes. — The action of the phosphorylative inhibitors atractylate and oligomycin on ATP-induced contraction of isolated pea mitochondria has been studied. Oligomycin has proved to be an efficient inhibitor of mitochondrial contraction; no effect is seen on the contrary upon addition of atractylate. Both atractylate and oligomycin inhibit completely oxygen consumption of mitochondria with succinate as substrate. On the base of these results it is postulated that the two inhibitors act upon different sites of the phosphorylative reaction sequence.     

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 other particulated cell structures, as revealed by electron microscopy.

In the mitochondrial preparation all of the three enzymatic activities investigated were found to increase rapidly during the first days of germination. The increase during the first 24 hours was almost as large when measured as specific activity (activity per mg protein in the mitochondrial fraction) than when measured on an absolute (i.e. per seed) basis; moreover, it was not significantly inhibited by puromycin or by actinomycin. The increase of the three activities during the following period of germination (second-third day) was accompanied by an increase of the protein nitrogen (per seed) in the mitochondrial fraction, and was consistently depressed by the protein synthesis inhibitors.

In the mitochondrial preparation all of the three enzymatic activities investigated were found to increase rapidly during the first days of germination. The increase during the first 24 hours was almost as large when measured as specific activity (activity per mg protein in the mitochondrial fraction) than when measured on an absolute (i.e. per seed) basis; moreover, it was not significantly inhibited by puromycin or by actinomycin. The increase of the three activities during the following period of germination (second-third day) was accompanied by an increase of the protein nitrogen (per seed) in the mitochondrial fraction, and was consistently depressed by the protein synthesis inhibitors.

These results, integrated with those of other investigations on the same material are in agreement with the hypothesis that the activation of metabolism in the endosperm during germination depends in a very early phase mainly on the transition of enzyme systems from an inactive to an active state; while in a second phase synthesis « ex novo » of enzymes and cell structures predominates.     

Ricerche Sul Rigonfiamento di Piccola Ampiezza in Mitocondri Isolati di Pisello

Abstract

Low amplitude swelling in isolated pea mitochondria. — The authors have studied the volume changes of isolated pea internode mitochondria occurring in a medium which allows the oxidative activity to proceed. With succinate as substrate respiratory control ratios as high as 9 have been obtained. They can be taken as an index of a tight coupling of mitochondria. The adding of succinate induces on the other hand a slight but continuous swelling which is strongly enhanced by ADP or ATP. Inhibitors of the respiratory chain like antimycin A and of the phosphorylation reactions like atractylate or oligomycin block completely the ADP or ATP-induced swelling. 2,4-dinitrophenol at 5×10^?6 M concentration exerts a strong inhibitory action on succinate oxidation and on swelling. Both actions of 2,4-DNP can be reversed by ATP. It can be concluded from these findings that the substances which slow down or abolish the oxidative and phosphorylative reactions inhibit also mitochondrial swelling. This type of volume changes appears therefore to be strictly energy-dependent.     

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.     

Rapporti Fra Endosperma ed Embrione Nella Germinazione di Pinus Pinea L.

Abstract

Endosperm embryo interrelationships during germination of PINUS PINEA L. (2nd Note). — Experiments have been performed with unripe fresh seeds paralleled with unripe stored seeds (50 days of storage).

The effect of storage is very similar to the effect of further permanence on the tree.

It is confirmed the importance of the endosperm in the germination process already put in evidence in the 1rst note.

The relationships existing between endosperm and embryo during the germination of the seed become more and more strict as the seed ripens, so that in a ripe seed the embryo develops in a normal seedling only in connection of its own endosperm.

In an unripe seed the embryo is uncompletely controlled by its endosperm.

Some remarks have been made about the degree of maturity of the different parts of the embryo.     

Primi Processi di Germinazione in Pinus Pinea L. var. Fragilis Du Hamel

Abstract

Early stages of germination in PINUS PINEA L. var. FRAGILIS Du Hamel. — The main stages of the hydration process preceeding germination and accompaning root elongation have been observed in Pinus pinea L. seeds, by means of vital colours (Congo red, neutral red, acid fuchsine).

The results are as follows:

a) water penetrates easily through the outer shell of the seed reaching its deepest layer which is less permeable to water. Two or three days were required in our experience for water could overcome this barrier.

b) The inner shell (known as « soft shell ») is almost water-proof and seems to draw water towards the micropilar pole of the seed, so that the first region of the seed which sucks up water is the micropile.

c) Through the micropile water enters the seed and imbibes the column, the pericolumn and the endosperm cells.

The endosperm swells with water until the seed shell blows up, because of the inside pressure. At this time water freely penetrates the seed everywhere.

In natural conditions we may infer that the first tissues which take contact with the soil water are the column and pericolumn. As a certain amount of time is required for penetration of water as far as the column (two or three days in experience conditions) germination starts only after a given amount of water is available in the soil for a certain period of time.

When seed hydration is performed the embryo root starts elongating and gets out of the seed.

The behaviour of the column, the pericolumn and the root cap during the early stages of germination are dexcribed.