376 CHLOROPLASTS AND CHROMOPLASTS CHAP. 14 



although only with the help of detergents such as sodium oleate, glycine, or urea. To 

 explain the necessity for detergents, Frey-Wyssling suggested that the chloroplast 

 lipides have no free hydroxyl groups. He assumed that their molecules are arranged 

 in mutually esterifying pairs (as shown in Fig. 46). 



The occurrence in the chloroplasts of acetone-exiractaUe phosphorus may also be 

 considered as an indication of the presence of phosphoUpides. The concentration of 

 phosphorus in the dry matter of clover chloroplasts is, according to table 14.VI, 

 about 0.7%. 



3. The Chloroplast Ash 



Earlier analyses of the mineral components of green plant tissues, 

 e. g., the analyses of Colin and Grandsire (1925), dealt with whole green 

 leaves. Neish (1939) made the first attempt to analyze the ash of 

 chloroplasts separately from that of the cytoplasm. His results are 

 given in table 14. VI, together with those of Menke (1940^). 



According to Neish, the alkaline ions (and chlorine ions) are concen- 

 trated in the cytoplasm and the cell sap; but Menke denied the absence 

 of potassium in the chloroplasts, and attributed Neish's results to losses 

 incurred in the washing of the chloroplastic matter. He pointed to the 

 immediate effect of potassium supply on the photosynthesis of potassium- 

 starved algae (Chapter 13, page 336) as an evidence for the penetration 

 of potassium into the chloroplasts. According to Neish, the alkaline 

 earth metals, including magnesium, are also more abundant outside than 

 inside the chloroplasts. (This result has a bearing on the problem of 

 the location of the alkaline earth carbonates, discussed in chapter 8.) 

 According to Javillier and Goudchaulx (1940), the proportion of leaf mag- 

 nesium concentrated in the chloroplasts can vary between 0.9% (Pinus 

 7naritima) and 26% {Triticum vulgare). Even in chloroplasts, most of 

 the magnesium is extractable by trichloroacetic acid and is thus not a 

 part of chlorophyll. 



Phosphorus is slightly more abundant in the chloroplasts than in 

 other parts of the leaf. A considerable part of phosphorus is extractable 

 by acetone, and may be a component of phosphoUpides. According to 

 Granick, 40% of the lipide-bound phosphorus of the leaves is found in 

 the chloroplasts. 



Important is the accumulation of the heavy metals, iron and copper, 

 in the chloroplasts, shown by table 14. VI. The presence of iron was 

 first demonstrated by Moore (1914), who stained chloroplasts with 

 hematoxylin (after having extracted chlorophyll by means of alcohol). 

 The hematoxylin reaction is characteristic of simple iron salts, and is not 

 given by complex organic compounds, e. g., hemin derivatives. Noack 

 (1930) found that 6% of leaf iron is soluble in water and can he identified 

 l)y means of potassium thiocyanate. Griessmeyer (1930) and Wieler 

 (1938) observed that the proportion of water-soluble iron in leaves can 



