Accrescimento Delle Plantule Di « Pinus Nigra » Arn. Di Diversa Provenienza (Nota preliminare)

Abstract

Growth of PINUS NIGRA Am. seedlings of different provenance. (Preliminary communication). — Pinus nigra seedlings from different provenance showed, during the first weeks of life, a different growth in height, irrespective of the photoperiod employed. Long night conditions were, on the whole, more favourable then short night conditions to their height growth.

The test failed to show the existence of a significant interaction between photo-period and provenance.     

Attività Fotosintetica di Alghe Marine Nella Grotta Delle Viole (Isola S. Domino - Tremiti)

Abstract

Photosynthetic rates of some algae in the marine cave « Grotta delle Viole » (Is. S. Domino - Tremiti). — The « Grotta delle Viole » is one of the several marine caves located along the calcareous rocky southern littoral of the Island S. Domino (Tremiti) in the Adriatic Sea. Morphologically this cave is a tunnel, which connects the open littoral sea with a little bay. Availing of these environmental factors, we have chosen three stations to measure the photosyn-thetic yield, under completely natural conditions, of algae particularly important for some marine communities, described in an other paper (see, Pignatti S. et al. 1967). In station 1 (fig. 1) we have a biotope with strongly reduced light and in the neighbouring stations 2 and 3, two biotopes exposed to sun-light. We have studied three species living in dark places (« Peyssonelia » cfr. « harveyana », « Palmophyllum crassum » and « Pseudolithophyllum expansum » two of well lighted habitas (« Padina pavonia » and « Dictyota dichotoma » and one of intermediate place (« Codium difforme ») Some information on the optical conditions of the seawater have been obtained with a photoelectric cell, filters were used to measure the red and blue light penetration (Tab. 1, 2). This part of the Adriatic Sea is characterized by high penetration of blue light. In the cave this light is highly predominant. The photosynthetic rates were measured in natural conditions by determining the output in time O₂ using the Winkler method (Tab. 3) and the CO₂ changes by measuring pH-changes in short time intervals with an original method using a submarine incubation cell, of our design, equipped with the electrodes of a pH-meter and a spot-light galvanometer as measure instrument. The data obtained with the latter method have been statistically analized, their significance discussed and reported in Tab. 4. On the basis of the results, the species, which are confined in places with reduced light intensity, show a low but measurable photosynthetic surplus only in their natural habitats, transferred in high-light intensity they show a deficit. This fact can suggest the hypotheses: deactivation of the chlorophyll in green and blue light or competitive inhibition due to the presence of accessory pigments. The species of sunny habitats transferred in low-light intensity show an assimilatory deficit, that in this case, with great probability, is due to the progressive reduction of the photosynthetic process. These considerations explaine also the observed distributions of the species and of the algal communities (fig. 1), since each of them is connected with a light optimum. It seems important moreover to note that here, for the first time, data are given also on photosynthetic activity of Lithothamnia.     

Ricerche Sull'Azione Inibente di Alcune Antiauxine Sull'Attività di Deidedrogenasi Delle Frazioni Solubile E Mitocondriale di Estratti di Tessuti di Piante Superiori

Summary

Inhibiting effect of antiauxins on some dehydrogenare enzyme systems in the soluble and in the particulate fractions of extracts from plant tissues.

The effect of several antiauxins (trans-cinnamic acid, diphenylacetic acid, 2–4 dichloroanisole, b-phenylpropionic acid, maleic hydrazide) on dehydrogenasic systems in enzymic preparations from higher plant tissues (cauliflower, pea, artichocke) has been investigated. Dehydrogenase activity has been determined, in the soluble (glucose-6-phosphate) as well as in the particulate (malic TPN linked, malic DPN linked, succinic dehydrogenases) fraction of the protoplasma, by the tetrazolium (used «in vacuum») and the Thunberg methods. Mitochondrial preparations have been obtained through repeated precipitations at 20.000 × g., in the cold, in 0,5 M sucrose.

All of the antiauxins tested, at concentrations ranging between 60 and 400 p. p. m., clearly inhibited dehydrogenase activity, both in the soluble as in the mitochondrial systems. Inhibition appeared non competitive, and indipendent from coenzyme concentration; it was more evident at lower pH values, and it increased with pretreatment of the enzyme with the antiauxins, in the absence of substrate.

These results are interpreted as an evidence for the capacity of antiauxins to act directly on fundamental metabolic systems, even in absence of auxin.

The lack of specificity and the characteristics of the inhibiting action of antiauxins on dehydrogenase systems suggest that they could act through the inactivation of some chemical group of general diffusion and importance among the enzymes of the class here investigated; very probably, of -SH groups.