CHLOROPHYLL A\D THE CHLOROPLASTS 2>72> 



TABLE 47 



Chlorophyll in 10 Grams of Various Leaves Before and After Photosynthesis. 

 5 Per Cent CO2 and About 75,000 Lux. (From Willstatter and Stoll.) 



Duration of Chlorophyll, mg. 



Plant Temp. Experiment Before After 



Prunus Laurocerasus 30° 6 hours 12.2 12.4 



30° 22 '' 9.4 9.5 



Hydrangea opulodes 30° 6 " 9.2 9.1 



Pelargonium zonale 40° 6 " 12.5 12.8 



synthesis. Englemann «^ as well as Kohl ^^ thought that carotin played a 

 role, along with chlorophyll, in photosynthesis, hut there has been little 

 evidence to support this view. Willstatter and Stoll consider that the yel- 

 low pigments play no role in photosynthesis. They base this opinion 

 upon the fact that the rate of photosynthesis is altered by very little when 

 a screen of a solution containing the yellow pigments is interposed be- 

 tween the leaf and the source of light. This evidence may be of sig- 

 nificance in connection with the optical properties of the yellow pigments, 

 but can hardly be brought to apply to a possible chemical function of 

 carotin and xanthophyll in the photosynthetic process. In Table 48 are 

 given the results of Willstatter and StoU's analyses of cherry laurel 

 leaves before and after a period of photosynthetic activity, showing the 

 unaltered chlorophyll-content and the change in the yellow pigments. The 

 experiments were carried out with 5 per cent carbon dioxide, about 68,000 

 Lux and at 31-32°. 



TABLE 48 



Effect of Photosynthesis on the Chlorophyll Components and on the 

 Carotinoids. (Willstatter and Stoll.) 



Content in mg. of 10 grams 

 Fresh Leaves 



Duration of Chloro- Chloro- Xantho- q5 q£ Q^-^^ 



Illumination phyll a phyll b Carotni phyll b x c -h x 



Unilluminated 7.2 2.2 0.87 1.65 i.i 0.56 2.3 



22 hours 7.1 2.4 0.63 2.29 3.1 0.39 2.0 



It is still to be determined whether a change in the carotinoid-content 

 during photosynthesis, as reported by Willstatter and Stoll, is of signifi- 

 cance in the photosynthetic reaction. Under the conditions of the experi- 

 ment, there was a high rate of photosynthesis, so that conditions may 

 have been favorable for the oxidation of the carotin. Willstatter and 

 Stoll also showed that during active respiration in the dark (30-37° for 



a c 



48 hours) there was no change in the Q r and O - ratios. 



Wlodek '° has examined various leaves spectroscopically and found 



•« Englemann, Bot. Zcity.. 45, 393, 409, 425, 441, 457 (1887). 



■^Kohl, Ber. bot. Ges., 24, Z22 (39) (1906). 



"Wlodek Bull Acad. Polonaise Sci. et Let. Ser. B. Sci. Nat., 1920, 20; 1921, 143. 



