Some data on the growth physiology of Chlorella studied by the technique of synchronous culture

1. Using the technique of synchronous culture, biochemical events occurring in the life cycle of Chlorella were investigated with reference to the change in contents of major elements (N, P, K, Mg, and S), crude protein, lipides, carbohydrates, and ash, and also with special reference to the effect ... Ausführliche Beschreibung

1. Person: Hase, E.
Weitere Personen: Morimura, Y.; Tamiya, H.
Quelle: in Archives of Biochemistry and Biophysics Vol. 69 (1957), p. 149-165
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Sprache: English
Veröffentlicht: 1957
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Anmerkung: Copyright: Copyright (c) 2005 Elsevier (USA)
Zusammenfassung: 1. Using the technique of synchronous culture, biochemical events occurring in the life cycle of Chlorella were investigated with reference to the change in contents of major elements (N, P, K, Mg, and S), crude protein, lipides, carbohydrates, and ash, and also with special reference to the effect of deprival of each major element from the medium.2. The life cycle of algal cells was divided in seven successive stages as follows: (a) ''nascent dark cells'' (D"n) which are the young cells newly produced from mother cells; (b) ''active dark cells'' (D"a), the most chlorophyll-rich and photosynthetically active cells which are derived from nascent dark cells when illuminated; (c) cells of transient stage between ''dark'' and ''light'' cells (D ~ L); (d) immature light cells (L"1) which are large in size but not yet ripe enough to perform cell division when incubated in the dark; (e) half-mature light cells (L"2) which can only partially divide when kept in the dark; (f) mature light cells (L"3) which can completely divide when incubated in the dark; and (g) fully ripened light cells (L"4) which are at the stage immediately prior to the process of cell division.3. The major nutrient elements were assimilated by algal cells in more or less different manners during the course of normal life cycle. In terms of percentage of dry weight, nitrogen content was the least variable, showing only a slight decrease at the stage of D ~ L; the phosphorus content decreased at stages D"a and D ~ L, and increased at stages L"1 and L"2; the sulfur content decreased considerably as the cells changed from D- to L-stage, and increased markedly as L"3 transformed into L"4.4. The percentage of crude protein remained almost constant throughout the life cycle, while lipide and carbohydrate contents varied more or less irregularly.5. The effect of the deficiency of each major element was investigated using normally grown D"a-cells as the starting material of synchronous culture. It was revealed that the growth of D"a-cells was sooner or later retarded in the absence of major elements. The retardation of growth occurred most strongly in the N-free and P-free media, less markedly in the K-free and S-free media, and most insignificantly in the Mg-free medium. Except in the case of S-deficiency, the cells grown in the absence of each major element could perform cell division, giving rise, however, to more or less unhealthy daughter cells. The average number of daughter cells produced from one mother cell was: 2.4 in N-free medium, 3.5 in P-free medium, 5.1 in K-free medium, and 6.4 in Mg-free medium, compared with 6.0-6.5 in the case of normal culture. The daughter cells formed in N-free and Mg-free media were profoundly etiolated, while those produced in P-free and K-free media looked normal in color. They were either unable to grow further (as in the case of N-deficiency) or could only slightly grow, and were all incapable of performing further cell division.6. A peculiar phenomenon was observed when the synchronous culture was run in S-free medium. In this case the starting D"a-cells grew apparently normally until the earlier stage of light cells, but unlike the cells grown in the absence of other major elements, they were entirely incapable of performing cell division. This fact, together with the observation that the assimilation of sulfur occurred mainly at the stage of light cells, indicates that sulfur plays some essential role in the process of cell division. The capacity of cell division, which had been lost in the absence of sulfur, could be restored by subsequent supply of sulfate and nitrate and by illuminating the cells with the provision of CO"2-enriched air.
ISSN: 0003-9861

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