PROTEINS AND LIPOIDS IN CHLOROPLASTS 



373 



chloroplasts (in all growth periods). According to Galston, this is 

 equally true of green and of chlorotic leaves. According to Granick's 

 analysis, 80% of the chloroplast nitrogen is contained in proteins, 7% 

 in compounds soluble in trichloroacetic acid (amino acids), 10% in 

 chlorophyll (a very high value!) and 3% in alcohol-ether soluble com- 

 pounds (nucleophosphatides?). Comar (1942) found 11% of total 

 chloroplast nitrogen in "lipoids" (including the pigments), of which less 

 than one-third was a part of chlorophyll. 



Granick's figures indicate that between 24 and 32% of all spinach 

 leaf proteins are contained in the chloroplasts; Hanson (1941) found a 

 similar figure (36%) for Phalaris tuherosa. Table 14.11 gives the more 

 detailed results of Menke (1938). Chibnall (1939) estimated that 

 cytoplasm and chloroplasts contribute equal amounts to the total protein 

 content of spinach leaves. 



The proportions of proteins and "lipoids" in different parts of the 

 leaf are shown in table 14. Ill, which includes the results of Chibnall, 

 Menke, Bot, Hanson, and Comar. 



Table 14. HI shows an approximate agreement between the data of 

 Chibnall, Menke, Bot and Comar on spinach leaves, and those of Bot 

 on Latyrus and Neish on TrifoUum; the chloroplasts of all these species 

 contain 35-55% proteins and 18-32% "lipoids." The large chloroplasts 

 of the sensitive fern, on the other hand, which carry 8.4% starch, differ 

 considerably in composition — they contain only 7% of ether-soluble 

 materials. 



The study of the specific nature of the chloroplast proteins has hardly 

 begun. An analysis of the amino acids residues, given by Chibnall 

 (1939), is reproduced in table 14.IV. 



Table 14.IV 

 Analysis of Spinach Leaves fob Amino Acids (after Chibnall) 



