Acta Botanica 3. (1957)

1957 / 1-2. szám - BÖSZÖRMÉNYI E. - BÖSZÖRMÉNYI ZOLTÁN: N and P nutrition and the physiological age of Lemna minor L.

N AND P NUTRITION AND THE PHYSIOLOGICAL AGE OF LEMNA MINOR L. By Mrs. E. Böszörményi and Z. Böszörményi INSTITUTE OF PLANT PHYSIOLOGY, THE EÖTVÖS LORANO UNIVERSITY, BUDAPEST (Received January 1, 1956) In the last two years one of the authors in dissertation dealt with certain features of the mineral nutrition of Lemna minor, with the rate of its growth and its development. In this paper the details connected with the problem of the physiological age are reported. It was the work of Ashby and his collaborators lasting over two decades (from 1928 on) that aroused interest for the vegetative multiplication of the Lemnaceae. They have ascertained not only that the multiplication of a frond is not unlimited, but that it dies after having produced a certain num­ber of daughter fronds. The length of age of Lemna fronds is determined by species characteristics and environmental factors. The successive daughter fronds, however, are not identical. The most conspicuous difference between them is the progressive diminution in their size, in their area surface. The smaller fronds, which have been produced later, are also more short-lived and produce fewer fronds per plant. Thus during their production the mother frond had undergone development i. e. ageing, its physiological age had altered. The sizes of the daughter fronds produced by the last one which is smaller than average, again increases, hence ageing is followed by a cyclic rejuvenation, according to Krenke’s theory of cyclic development. Out of environmental factors the effect of temperature and light intensity on the vegetative multiplication of Lemna minor has already been examined some time back. The rise in temperature has reduced the length of life, while the effect of lighting was — within certain limits — nearly nil. Nor did the length of day affect the length of life. Ashby and his collaborators came to the conclusion that during the pro­duction of daughter fronds some factor in the mother frond becomes exhausted, thereby causing the death of the frond. They have suggested that this factor is some special metabolic product and have attempted to identify it by adding different substances to the culture solution. They tried in vain to examine the effect of adenine, auxins and antiauxins. These factors did not affect ageing. At the beginning of 1954, when analysing the above researches, we came 1 Acta Botanica III/1—2.

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