466 



SMITH, KUPKE, LOEFFLEK, BENITEZ, AHKNE, GIESE 



at about 0°C. The a})Sorption spectrum of the supernatant was then 

 measured. A portion of the extract, after being illuminated, was again 

 examined spectrophotometrically. Examples of the absorption spec- 

 tra of the extracts obtained before and after they had been illumi- 

 nated are shown in Figs. 1 and 2. The chief result of these experiments 

 is that the protochlorophyll holochrome, even though separated from 

 the leaf or cotyledon, is transformed to chlorophyll-a holochrome by 



600 



700 800 



WAVELENGTH 



900 



Fig. 2. Tlie transformation of protochlorophyll holochrome to chloropiiyll-o 

 holochrome in a glycerine extract of etiolated squash cotyledons (Hubbard squash). 

 The glj'cerine e.xtract was passed through a French-Milner homogenizer (4). 



light. These curves also show that the protochlorophyll and chloro- 

 phyll holochromes from various sources possess different spectral 

 properties. For instance, in glycerine extracts from different dark- 

 grown plant materials, the absorption maxima of the protochlorophyll 

 holochrome and of the chlorophyll-a holochrome derived therefrom 

 he at different wavelengths: In barley leaves the respective maxima 

 lie at 5«650 and 080 ni/x; in bean leaves at 640 and 675 mn; in 

 squash cotyledons at 645 and 680 niju. These results indicate that the 

 holochromes from various sources are not identical. They probably 

 differ in respect to the nature of the carrier or of the union lietween 

 pigment and carrier rather than in the structure of the pigmented 

 component. 



