292 ALLEN, WHATLEY, ROSENBERG, CAPINDALE, ARNON 



The products of carl)on dioxide reduction by the broken chloro- 

 plast system, shown in Fig. 2, resembled in most respects those 

 obtained from whole chloioplasts. The proportion of insoluble material 

 was smaller, but could be increased by the addition of soluble starch, 

 suggesting a deficiency of primer for starch synthesis. Malic and aspar- 

 tic acids have not been found. Phosphogly eerie acid, which was pres- 

 ent only in traces among the compounds formed by whole chloro- 

 plasts, was found to be a more conspicuous product of the broken 

 chloroplast system. 



Discussion 



Witt : W'liut al)out the size of the broken chloroplast? 



M. B. Allen: That is a little hard to answer. There is a progressive change. One 

 starts off with a chloroplast that is smooth in outline, rather elliptical. The first 

 thing that happens is that the smooth outline is blurred and the chloroplasts begin 

 to look irregular. As they are allowed to stand in water the whole structure more 

 or less falls apart and we get globs and bits. 



Witt : How were the chloroplasts heated? 



M. B. Allen: The chloroplasts were not heated. The chloroplast extract was 

 heated at 100°C. for 90 seconds. 



James Smith : Do j^ou get starch? 



M. B. Allen: We get some starch. For a reason that we don't fully understand, 

 the quantity- of starch formed by the broken chloroplast is far less than that formed 

 by whole chloroplasts. We find that we can increase it a bit by adding a little sol- 

 uble starch, but in no case does it rise beyond 30% or 40% of that obtained with 

 whole chloroplasts. 



Fuller: I would like to make one comment about whether grana contain car- 

 boxylating activity. Dr. Allen pointed out that there is no direct evidence for this 

 in the green leaf. However, work has been done in our laboratory which indicates 

 that, as far as carboxylating enzymes are concerned, the grana (if you want to 

 call them grana) of Rhodospirillum, and of blue-green algae as well, prepared in 

 the same way, do contain at least the carboxylase of photosynthesis. Other ob- 

 servations can be added to this. By bleaching the cells of Euglena with streptomy- 

 cin and growing Euglena in the dark, at least the primary carboxylating enzyme is 

 lost. There are cases in albino plants where the same loss of activity has been ob- 

 served with the carboxylating enzyme and some additional enzymes concerned in 

 photosynthesis. 



Strehler : Dr. Allen, how does the maximum rate of CO2 fixation obtainable with 

 your chloroplasts compare to photosynthesis in the whole cell, e.g., on a chloro- 

 phyll basis? 



M. B. Allen: This is a slightly difficult question to answer for leaves. We have 

 this on our agenda to investigate. 



Amon: This question comes up very often and, as Dr. Allen has indicated, we 

 are going to do the experiment, but not because we believe it is important at this 



