3 CHLOROPLASTS 25I 



else. By this method Heierle (1935) finds for Amersfoort tobacco at the 

 end of July, for instance, per square metre of leaf surface: chlorophyll a 

 147.5 n^g' chlorophyll ^53.8 mg, carotene 37.2 mg and xanthophyll 17.8 

 mg. This represents the famiUar molecular ratio of 3 : i for the green pig- 

 ments and roughly one molecule of carotenoids to every two chlorophyll 

 molecules (about 1/3 molecule of carotene and 2/3 molecule of xanthophyll). 

 By means of chromatographic adsorption Seybold (1941) made comparative 

 measurements and found that the molar ratios just given do not invariably 

 exist between the pigments. Chlorophyll h, for instance, may be present in far 

 smaller quantities, or may not occur at ail, this applying notably to certain 

 algae (Seybold, Egle and Hulsbruch, 1941). Instead, those groups of algae 

 may contain other varieties of the green pigment, such as chlorophyll c or 

 chlorophyll (/(Aronoff, 1950). 



c. Suhmicroscopic Structure of the Chloroplasts 



State of chlorophyll in the chloroplast. Granular chlorophyll and mole- 

 cular chlorophyll solutions (in acetone, alcohol, etc.; Fig. 128a) show 

 red fluorescence when exposed to light rays ; the fluorescence is pro- 





AL (OhJs 



c 



Fig. 128. Chlorophvll molecule, a) Molecular dispersion; b) colloid particle; <r) adsorbed 



on a monomolccular lecithin layer. 



portional to the intensity but independent of the wavelength of the 

 incident light (Wassink, Vermeulen, Reman and Katz, 1938). On 

 the other hand, colloidal chlorophyll solutions do not fluoresce; they 

 can be obtained by the dilution of molecular solutions with water. The 

 chlorophyll molecules then assemble, on account of their partial 



