C. STACY FRENCH 61 



Fluorescence Spectra of Pigments in Live Plants 



Chlorophyll a 



The fluorescence spectrum of chlorophyll a in ether is compared in 

 Fig. 10 with that of chlorophyll a in a very thin layer of plant mate- 

 rial, sea lettuce (Ulva). The fluorescence spectra, like the absorption 

 spectra, of chlorophyll pigments are shifted toward shorter wave- 

 lengths when taken out of the plant by organic solvents. The extent of 

 this shift is, however, different in plants which have been grown in 

 the light and in etiolated albinos that have very recently had their 

 chlorophyll formed from protochlorophyll by exposure to light. Table 

 I shows that the freshly formed chlorophyll a has its peak between 



TABLE I 

 Wavelengths of the Chlorophyll a Fluorescence Peak 



" Zscheile and Harris, 1943. 



* Todd, Virgin, and El Wakeel, unpublished. 



that of chlorophyll in solvents and of chlorophyll in light-grown plants. 

 Perhaps this freshly formed chlorophyll is not yet completely built 

 into its normal state in nature as a protein complex. 



Now we will see what happens to the fluorescence spectrum of 

 chlorophyll in living material when it is present in higher concentra- 

 tions. Figure 11 compares the fluorescence spectrum of a normally green 

 grape leaf with that of a white grape leaf that is apparently com- 

 pletely devoid of chlorophyll, as far as one can see by eye or by the 



