Il consumo di ossigeno in tessuti vegetali trattati con estratti lichenici

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Abstract
The rate of the 02 uptake in plants' tissues treated with lichens' extracts. Researches were made to determine the rate of the oxygen consumption and the Co2: 02 ratio in tissues treated with lichens' extracts. Germinating seeds, grown up roots and root tips of Allium cepa have been used as researche material. The lichens, whose action has been tested, are the following: Usnea barbata, Evernia vulpina, Evernia furfuracea, Evernia prunastri, Peltigera carina, Cladonia pyxidata. Phosphate solutions, buffered at pH 6,8 proved useful as extractive solutions. Measurements made with the Warburg-Barcroft microrespirometer showed a strong decrease of the oxygen absorbed and a remarkable alteration of the respiratory quotient; a particularly poisonous effect appears to be caused by Usnea barbata, as it is also evidenced by microscopical observations. Ev. vulpina, Ev. furfuracea and Ev. prunastri were also found to have a rather strong inhibitory action on tissues. As to Peltigera no antibiotic activity could be brought to evidence: the same with Cladonia pyxidata whose inhibiting power appears very dubious. The decrease of the amount of the oxygen absorbed and the alteration of the Co2:02 ratio were found to be in direct proportion to the lichens' extracts concentration and the time of treatment: the meristematic tissues were found to be the most affected, with a decrease of the 02 uptake below the 30% of the normal average values. The tissues reactivity to antibiotic agents reaches its highest degree according with the maximum of metabolic activity and drops at its lowest in relaxed metabolism pe riods. The A. thinks to be entitled to point out, besides the undeniable presence of antibiotic compounds in the lichens whose extracts caused such remarkable alterations in the gaseous exchanges, the importance of respiration measures as semeiotic indices of plants' metabolic conditions, Exapt to detect even the slightest damage caused by antibiotic agents.

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