VOL. 12 (1953) BIOCHIMICA ET BIOPHYSICA ACTA 23 



CORRELATION BETWEEN PHOTOSYNTHESIS AND 

 LIGHT-INDEPENDENT METABOLISM IN THE GROWTH OF 



CHLORELLA* /^^^^Al 



H. TAMIYA, T. IWAMURA, K. SHIBATA, E. HASE and T. NIHElf / iv05i>rfl \ C 

 The Tokueawa Institute for Biological Research, Tokyo ( Japan) XtZ- \ L.I Oi\ As\ Y lit 



^ ^ MASS. y^Q>, 



The growth of green plants in general may be regarded as being composeo'^st. tw 

 main processes, the light-dependent process, photosynthesis, and the light-independent 

 processes which involve an immense variety of biochemical and biophysical events by 

 which the primary photosynthetic products are converted into cell materials. Despite 

 the vast amount of work devoted to the analysis of specific reactions involved in the 

 growth of plants, few attempts have been made to correlate quantitatively photo- 

 synthesis and the dark process as a whole. Obviously, this is due to the enormous com- 

 plexity of the relationship between them, which is especially complicated in the higher 

 plants which have highly differentiated structures and grow under conditions difficult 

 to control experimentally. 



The matter appears in a somewhat different light when we deal with the simplest 

 form of green plant, such asChlorella, which has been recognized as excellent experimental 

 material for the study of photosynthesis ever since it was first used by Warburg in his 

 pioneer work in the field. Working with the culture of Chlorella ellipsoidea, we^ have 

 recently observed that the cells assume, in the course of their growth, two distinct forms 

 possessing widely different characters. The form, which we named "dark cells", is much 

 smaller in size, richer in chlorophyll, and more photosynthetically active than the other 

 form called "light cells". The dark cells with their well-organized photosynthetic 

 apparatus are strongly disposed toward photosynthesis, and, if provided with light and 

 adequate nutrient substances, grow into the light cells which in turn, under adequate 

 conditions, divide into a number of dark cells. This latter process occurs entirely inde- 

 pendently of light, thus embodying the essential feature of the light-independent phase 

 of growth mentioned above. The over-all growth process of the algae is accomplished by 

 the repetition of the mutual change between these two kinds of cells, and it may be 

 expressed most simply by the following formulae : 



T dark -r>, 

 L >nD 



* This work was supported by grants from the Ministry of Education, the Ministry of Inter- 

 national Trade and Industry, and the Mainichi Shimbun, Inc. A part of the theory described in this 

 paper was worked out by the senior author during his stay in Stanford, California, as a guest in- 

 vestigator of Carnegie Institution of Washington. The writers' warm thanks are due to the members 

 of the Institution for their interest and advice in the preparation of this paper. 



References p. 40. 



