696 



LIGHT ABSORPTION BY PIGMENTS IN VIVO 



CHAP. 22 



Fig. 22.31 A. Summer landscape photographed in infrared Hght (after Mecke and 



Baldwin 1937). 



graphs (fig. 22.31 A). Figure 22.32 shows the reflection spectra of three 

 leaves of the same species, but of different ages, as given by Shull (1929). 



Table 22.11 



Reflection Transmission and Absorption of Light by Leaves 

 OF Fraxinus excelsior (after Pokrovski 1925) 



Wave length, m,. 480 500 550 600 620 650 



Reflected, % 2.5 4.1 11.5 7.7 6.7 5.4 



Transmitted, % 6.4 8.6 17.5 12.4 11.1 9.8 



Absorbed, % .91.1 87.3 71.0 79.2 82.2 84.8 



The figures of Pokrovski (1925), given in Table 22.11, illustrate the 

 fate of light of different wave lengths falling on a leaf of Fraxinus excelsior. 



Figure 22.33 shows the reflection spectra of autumnal leaves of different colors 

 (averages for 20-80 different species), as given by Loomis, Carr and Randall (1941). 

 Spohn (1934) observed that the position of the absorption maximum of chlorophyll is 

 shifted in autumnal leaves, from 670 to about 660 niju, probably indicating the liberation 

 of chlorophyll from the pigment-protein-lipide complex present in photosynthetically 

 active cells. 



