348 PHOTOSYNTHESIS 



in the yellow (578 |X|i), 9 times the absorption in the red (660 \i\i) and 

 23 times in the blue (436 fxfx). The yellow pigments, which were included 

 in the solutions examined, it was found, do not absorb any red, yellow 

 or green light; in the blue-green region of the spectrum the yellow pig- 

 ments are responsible for about 46 per cent and in the blue for about 30 

 per cent of the absorption of the mixture of leaf pigments. 



In Table 43 are given some results of Tswett ^^ who made spectro- 

 photometric measurements of the two chlorophyll components in alcohol 

 solution. An Englemann microspectrophotometer with a grating and a 

 Nernst lamp, as a source of light, were used. 



TABLE 43 



Per Cent Transmission of Light of Different Wave Length by Chlorophyll 

 a AND b in Alcoholic Solution. (From Tswett.) 



Chlorophyll b- 



Chlorophyll a I H 



_-A_ 



I J/J„ -k J/Jo -K J/J„ 



680-690 53.5 _ _ _ _ 



675-680 15.0 _ _ _ _ 



670-675 4.8 — — — — 



660-670 1.9 660-670 7L5 665-675 74.5 



657-660 7.9 650-660 54.2 655-665 6L0 



650-655 18.0 640-650 45.8 645-655 48.0 



640-650 32.1 630-640 65.8 635-645 53.0 



620-640 51.2 — — — — 



500-510 74.2 _ _ _ — 



490-500 72.4 — — 490-500 71.8 



480-490 66.5 — — 485-490 54.0 



470-480 63.0 — — 480-485 41.7 



460-470 53.8 475-480 34.5 475-480 40.2 



555-460 42.2 470-475 27.3 470-475 26.3 



450-455 ?>?>.?> 460-470 15.7 460-470 18.8 



445-450 20.0 450-460 20.1 450-460 21.7 



440-445 10.6 440-450 \ ^^ 440-450 40.2 



430-440 0.9 430-440 / ^'^'^ 430-440 40.3 



420-430 2.4 — — 420-430 62.0 



As can be seen in Table 43, Tswett found maximum absorption in 

 the blue end of the spectrum. Ursprung summarizes the results of vari- 

 ous observers of the location of the maximum absorption of chlorophyll 

 solutions thus : Reinke, 676-663 \i\i ; van Gulik, 673-666 \i\i ; Englemann, 

 665-660 \i\i, and Donath, 638 \i\i. Ursprung reports maximum absorption 

 with a narrow slit at 661 yi\i, and with a wide slit at 637 [X[i. Iwanowski " 

 reports maximum absorption of chlorophyll a at 665 \i\i; this is also the 

 location of the maximum absorption of mixtures of the two chlorophyll 

 components. He also finds a second maximum absorption in the blue at 

 440 [iji. 



The bands of the absorption spectrum of a colloidal solution of chloro- 



" Tswett, Ber. bot. Ges., 25, 388 (1907). Ursprung, ihid., 36, 74 (1918). Engle- 

 mann, Zeit. zviss. Mikro., 5, 289 (1888). 



"Iwanowski, Ber. bot. Ges., 32, 433 (1914). 



