72 



FLUORESCENCE SPECTROPHOTOMETRY 



it is evident that it is only the chlorophyll fluorescence and not the 

 fluorescence of phycoerythrin and phycocyanin that is influenced by 

 the Kautsky effect. It thus appears that the products of photosynthesis 

 which somehow or other quench fluorescence act only upon chloro- 

 phyll, either because only chlorophyll is sensitive to such quenchers or 

 because the immediate products of photosynthesis are more closely 

 associated with chlorophyll than with the other pigments. 



A New Leaf Pigment Found by Fluorescence 



A paper by Goodwin, Koski, and Owens (1951) describes a new 

 leaf pigment, traces of which are present in the cells surrounding the 



560 600 640 680 



WAVE LENGTH IN m/j 



720 



Fig. 22. Fluorescence of the methanol extracted epidermis of Vicxa (solid line), 

 compared with uroporphyrin I octamethyl ester in methanol (dotted line). 

 (Goodwin, Young, and Owens, 1952.) 



guard cells of certain species of Vicia. This pigment was discovered 

 with a fluorescence microscope and was reasonably well identified 

 solely by fluorescence spectroscopy. The guard cells making the 

 stomata contain chlorophyll and show a red fluorescence. In the cells 

 around them there are small bodies having a somewhat more orange 

 fluorescence. A little piece of the epidermis peeled off from the rest 

 of the leaf shows chlorophyll fluorescence and also another peak at ap- 

 proximately 615 m/x. Some of this epidermis was treated with methanol 

 to remove the chlorophyll, but the new fluorescing pigment was not 

 extracted by methanol. Figure 22 shows the fluorescence spectrum of 



