AZione Della Luce Sull'Assorbimento Salino Da Parte Di Tessuti Clorofilliani In Ambiente Privo Di CO2

Abstract

Effect of light on uptake by photosynthetic tissues in the absence of co₂. — The effect of light and of CO₂ on the uptake of ⁸⁶Rb and ^-32P by isolated leaves of Elodea canadensis has been studied. The uptake of both these ions is strongly stimulated by light both in the presence and in the absence of CO₂. In the case of phosphate, light stimulates uptake and inhibits the leakage of the ion from the tissues.

These results which confirm and extend the results of other Authors, support the conclusion that the stimulation by light of active uptake of solutes by green tissues is physiologically relevant. Furthermore, they suggest that the utilization of light energy for active uptake does not depend on CO₂ fixation and assimilation.     

Aspetti Della Biocenosi Coralligena in Due Stazioni Dei Bacini Occidentale Ed Orientale Del Mediterraneo

Abstract

Facies of the coralligenous biocoenose in two stations of the Western and Eastern Mediterranean Basins. — The benthic comunities of circalittoral region have been studied by diving technique in the Western and Eastern Mediterranean Basins. The facies of the coralligenous biocoenose which show a larger difference between the two Basins are: 1) the communities of non calcareous algae in biotopes with constant direction depth streams and 2) the precoralligenous facies. These communities in the Aegean Sea are characterized by Sargassum linifolium, Cystoseira corniculata v. laxior, Caulerpa prolifera, Udotea petiolata, Dasycladus clavaeformis and by sponge Calix nicaeensis; in the Thyrrenean Sea by Laminaria rodriguezii, Cystoseira spinosa, Neurocaulon grandiflorum, Fauchea repens, Halymenia dichotoma, Callymenia reniformis and by the sponge Axinella cannabina. The environmental factors which determine these different facies in the circalittoral region of the two Mediterranean Basins are chiefly the temperature, the light intensity and the sedimentary rhythm.     

Althenia Filiformis Petit: Azione Della Temperatura e Dell'Acqua di Mare Sulla Germinazione

Abstract

Effects of temperature and sea water on germination behaviour of Althenia filiformis Petit seeds. - Germination capacity and energy of Althenia filiformis Petit seeds have been investigated, 90 and 180 days after ripening, to carry out a preliminary study on ecology of this species.

This species, halophite and hydrophyte, is spreaded along the coast shores of middle-west mediterranean sea and atlantic shores of Morocco, Spain, Portugal and France.

Seeds were soaked in the dark, at 10°, 20°, 30°C, in solutions at different salt concentration: sea water; sea water diluted in deionized water at ratios (v/v) 1: 2, 1: 4, 1: 8; sea water plus 26 gr/l NaCl; deionized water, as control.

The experimental results show that germination is reduced and delayed when seeds are soaked in progressively concentrated salt solutions; in sea water plus 26 gr/l NaCl seed germination is inhibited.

Seeds pretreated by soaking at 3°C for 10 days in sea water diluted (1:1) by deionized water did not show, when soaked in salt solution at weak and middle concentration, any delay in germination in comparison with unpretreated seeds. On the contrary, pretreated and unpretreated seeds sown in sea water at 30°C had shown, 180 days after ripening, a significant depression in germination values as compared with seeds sown at 20°C.     

Le Basi Anatomiche Dei Rapporti Nutritivi Tra Pianta Madre,Seme Ed Embrione

Abstract

The anatomical basis of the nutritive relationships between mother plant, seed, and embryo. — The morphology and anatomy of the fruits and seeds of the Angiosperms show a great variety of structures and adaptments, even within the same family, and one must be cautious in drawing generalized conclusions.

If we first examine the ovary we see that the single carpel receives three vascular traces from which the three main bundles originate, a dorsal and two ventral ones, all more or less reduced. Except in the case of laminar placentation the ovule traces are connected to the ventral vascular system, but often the entire vascular system of the ovary is anastomosed and therefore reticular. However especially when the placentae are at the centre or at the basis of the ovary, it is possible to detect a tendency towards a separation between the vascular system of the ovarian wall and that of the placentae.

The ovular bundle runs through the funicle reaching the chalaza, where it can either end or continue towards the micropyle with a single bundle or with a few branches or even forming a complete reticular envelope surrounding the ovule. The ovular vascular bundles are normally found in the outer integument.

The ovule is made of an inner part (nucellus), and an outer one (integuments). The integuments play a very important role in the processes of seed maturation, dormancy, and germination. They are isolated from the interior of the seed by a cuticle which is a common production of the inner integumentary epidermis, and of the nucellus. The cuticle is not present in the chalaza and can be dissolved in the micropylar region: through these two apertures nutrients can penetrate into the seed or haustoria can grow out of it. During the course of maturation these openings become closed by various means, often through the formation of a new cuticle or of a suberised chalazal plate.

The nutrients which pass through the chalaza penetrate into the nucellus where in some cases one can find some structures which facilitate the communications between the chalaza and embryo sac. The endosperm feeds at the expense of the nucellus but often it can establish a direct contact with the chalaza or the integuments or even the placentae. This occurs often thanks to haustoria.

The embryo is normally surrounded at first by a more or less liquid endosperm: in a second stage the endosperm becomes cellular and the embryo grows at its expense through the digestive activity of the cotyledonar epidermis.

From an anatomo-physiological point of view the following points seem of particular interest:

(I) The endosperm and the embryo show a remarkable autonomy in respect of the mother plant: from an anatomical point of view this is shown by the isolation of the endosperm and embryo by means of a cuticular covering or substitutive structures and by the interposition of nutritive tissues between the vascular system of the mother plant and the endosperm.

(II) Given the importance of the inner cuticle its presence and its constitution should be ascertained in the various species having also in mind the properties of selective permeability shown by the testa.

(III) Two nutritive mechanisms exist: translocation of nutrients via the vascular system and the nutritive tissues, and digestion of surrounding cells. In the digestive phenomena it is important to explain the mechanisms by which only the right cells are digested and not the others.

(IV) The embryo very frequently is immersed at first in a more or less liquid endosperm and is later surrounded by a compact tissue; the nutritive mechanisms are probably different in the two cases.

(V) Two endospermic zones are often distinguishable: one having an haustorial or at least a digestive or elaborative function, and being typically non cellular; another zone, typically cellular, forms a tissue which is sooner or later absorbed by the embryo. The cellularization of this zone seems to coincide with the establishment of polarity and with the beginning of maximum growth of the embryo.

(VI) The relationships between the inner seed and the integuments is complex and there is a correlation between the histoanatomical and biochemical changes of these two parts during seed development. The modifications undergone by the integuments are important steps also towards the preparation of the seed to the processes of dispersal, dormancy, and germination.     

Utilizzazione Di Afidi Per Il Prelevamento Della Linfa in « Cuscuta Epithymum »

Abstract

Use of Aphids for sampling the cell sap of Cuscuta epithymum. — A variety of Myzus persicae that feeds specifically on Cuscuta epithymum has been employed in a study of the translocation of nutrilites from the host, Trifolium repens, to the parasite, C. epithymum. If the host was exposed to an atmosphere containing C¹⁴,O₂, the Aphids feeding on the Cuscuta filaments became labelled very rapidly and to considerable extent. The analysis of the distribution of radioactivity in the Cuscuta filaments and the Aphids revealed that extensive degradation of the compounds and randomization of the label occurred in the insects.     

Osservazioni Morfologiche Ed Anatomiche Sull' Apparato Sotterraneo Della Carlina Acaulis L.

Abstract

Orservation on the morphology and the anatomy on the subterranean organ of CARLINA ACAULIS L. — The morphology and the anatomy of the subterranean organ of Carlina acaulis L. have been studied in relation to the structure of the analogous organ in Atractylis gummifera L. (Maugini, 1960). It has been shown that the two organs differ markedly: in Carlina there is an evident flattening and dissociation of the stem and a dual anatomical structure, related both to stem and to root.