PREFACE Vll 



tion of the intimate structure of the specimens (some striking pictures 

 obtained with this technique are reproduced in Chapter 38). 



Leyon,2 ^nd Vatter/^ have reported interesting new data concerning the 

 ontogenetic development of the chloroplast structure. 



Important new observations were made concerning the photochemical 

 activity of chloroplast preparations. Thomas and Haans"* thought that the 

 loss of much or all of the chloroplast stroma in the preparation of granular 

 chloroplast fragments from leaves may be responsible for their incapacity 

 to utilize carbon dioxide as photochemical oxidant. They accordingly pre- 

 pared macerates from stroma-free, laminar chloroplasts of Spirogyra, and 

 found that these preparations could take up manometrically measurable 

 amounts of carbon dioxide and liberate roughly equivalent amounts of 

 oxygen in light. 



Arnon and co-workers^ expanded, in a series of papers, the interesting 

 findings to which brief reference only could be made on pp. 1537 and 1982. 

 They found that whole chloroplasts, separated from protoplasmic particles 

 (mitochondria), as well as fragments of such protoplasma-free chloroplasts, 

 have very little aerobic metabolism — respiration and correlated ATP- 

 formation from morganic phosphate. On the other hand, they show evi- 

 dence of two photosynthetic processes — the uptake of CO2 (revealed by 

 tracer measurements), with C(14) incorporation in sugar phosphates and 

 carbohydrates (starch) and liberation of oxygen (measured manometrically, 

 after qualitative gas identification by luminous bacteria) ; and of anaerobic 

 formation of high-energy phosphate (''photosynthetic phosphorylation"). 

 The photochemical processes can be directed preponderantly towards 

 photosynthesis, or towards ATP accumulation, by varying external condi- 

 tions or adding appropriate inhibitors. 



In chloroplast fragments (as contrasted to whole chloroplasts) the 

 "photosynthetic" CO2 fixation could be observed only upon the addition 

 of an aqueous extract from chloroplast maceration. The anaerobic forma- 

 tion of ATP in light could be stimulated, in such fragments, by "co-factors," 

 which included Mg++-ions, vitamin-K type compounds {e.g., menandione), 

 riboflavin, and ascorbic acid, until it was much stronger than in intact 

 chloroplasts. The photochemical C02-incorporation was not stimulated (or 

 even mhibited) by these additions, with the exception of ascorbic acid. 

 The apparent necessity of the latter (in amounts much larger than that of 



2 Leyon, H., Exptl. Cell Reserch, 7, 609 (1954). 



3 Vatter, A. E., Thesis, Univ. of Illinois, 1955. 



* Thomas, J. B., and Haans, A. M. J., Biochim. et Biophys. Acta, 18, 287 (1955). 



6 Arnon, D. I., Whatley, F. R., and Allen, M. B., J. Am. Chem. Soc, 76, 6324 

 (1954); Allen, M. B., Arnon, D. I., Capindale, F. R., Whatley, F. R., and Durham, L. J., 

 ibid., 77, 4149 (1955); Arnon, D. I., Science, 122, 3157 (1955); Arnon, D. I., et al, 

 Gatlinburg Conference on Photosynthesis of the NAS, Oct. 1955 (in press). 



