Fig. 21. 



A young germling plant with a well-established rhizoid. 

 xs, cross section. 



has already started the process normally called 

 germination; it has begiin to grow out to form 

 the primary rhizoid. 



The next micrograph is a somewhat later 

 stage (Fig. 21). It is a young germling after 

 about 30-40 min in culture, which has the 

 rhizoid well started. It is probably longer than 

 it appears in the micrograph since a tangential 

 section makes it taper down, but it could be the 

 actual size. At this stage the germling looks 

 like a perfectly normal cell and, in fact, develop- 

 ment from this point involves mainly increase 

 in size with branching and multiplicity of the 

 rhizoids, in the absence of cell division. 



DEERING: How big is this germling? 



LOVETT: The spore body is about 7x9 

 microns, and this is roughly the same, about 8 

 microns in diameter before it starts to grow. 



DEERING: What are the long, slender lines 

 in the cytoplasm? 



LOVETT: That is the endoplasmic reticu- 

 lum. It is fairly prominent here but not at some 

 other stages. 



KAHN: Is that the nucleolus? 



LOVETT: Yes, they have a large nucleolus 

 that is always present. You remember seeing the 

 spore? It was small and compact in the spore. 



I'll have more to say about it in a moment. 



DEERING: In published results, Cantino 

 mentioned that this plant seemed to separate 

 into two cells. 



LOVETT: That is not at this stage; it 

 occurs later, during the time when spores are 

 formed at the end of the growth phase. 



DEERING: How much later is it? At what 

 point can you really say that you've got division 

 into two cells? 



LOVETT: There is none at the stage I'm 

 talking about. That occurs only at the end of the 

 growth phase. 



CANTINO: I didn't speak of cell division, 

 only nuclear division. 



DEERING: I'm talking about the two cells, 

 the basal one and the one full of nuclei. 



LOVETT: That is just before spore are 

 released and is in the other experiments we 

 were doing. I didn't discuss it because it is 

 obscure and hard to see and we haven't really 

 done anything with it. 



We can easily get reasonably well- syn- 

 chronized cultures of the germinating spores, 

 at cell densities of about 10^ cells per liter, all 

 doing very nearly the same thing at the same 

 time. The synchrony is not, however, quite as 

 good as we have obtained from zoospore dif- 

 ferentiation. 



The next two figures illustrate the pattern 

 of synthesis during early stages of germination. 

 The cells appear to lose some dry weight during 

 the first hour of germination (Fig. 22). They are 

 so fragile, however, that we are sure some ma- 

 terial was lost while trying to collect the cells 

 and measure their dry weight. Thus, part of the 

 drop may be artificial. After the first hour, the 

 dry weight increases linearly for a matter of 6 

 or 7 hr at least. Figure 22 also shows DNA syn- 

 thesis during the same stage, and you will notice 

 that it increases nicely in a step function from 

 one level to twice as much in a 2 hr period. Nu- 

 clear division, which still puzzles us, occurs 

 during about the first hour of the 2 hr period of 

 DNA synthesis. We are not sure what this 

 means, but it may indicate that our culture is not 

 as synchronized as it appears. This, however, 

 remains to be seen. It does go through this first 

 nuclear division in a reasonably synchronous 

 fashion. 



Figure 23 roughly illustrates the increase 

 in total RNA and total protein during germina- 

 tion and early growth. Net RNA increase is not 

 apparent for about 20 min, and new protein in- 

 crease is not detectable until about 40 min. 



Figure 24 is a summary diagram which we 



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