CHLOROPHYLL AXD THE CHLOROPLASTS 349 



phyll are shifted toward the red end as compared to those of a true 

 solution of chlorophyll. This becomes evident in the following table of 

 Willstatter and Stoll for the absorption spectrum of 0.044 gram chloro- 

 phyll a in 1000 cc. of water containing 1 per cent of acetone (0.001 mole 

 in 20 liters) when compared to the table giving the absorption spectrum 

 of a true solution of chlorophyll a. 



-Thickness of Layer in mm. 



10 20 40 



Band I 692—664 



•' II — 



" III — 



" IV — 



" V — ^ 



'' Y^ ■:.•••• ] 466... 455— \ 



End absorption J J 



It is interesting that the absorption spectrum of green leaves also shows 

 the shifting of the bands toward the red end of the spectrum as com- 

 pared with those of a solution of chlorophyll in ether or acetone. In order 

 to obtain the absorption spectra of leaves it is necessary to remove 

 the gases from the intercellular spaces. This can be accomplished by 

 displacing the air with water by drawing out the gas under a vacuum. 

 The leaves in this condition are more transparent and the light-absorp- 

 tion of a number of superimposed leaves can be determined. The dififer- 

 ence in the position of the absorption bands between leaves and chloro- 

 phyll solutions can thus be determined. 



The condition of chlarophyll in the living plant. The location of the 

 absorption bands of chlorophyll in true and colloidal solution and in the 

 leaf has been used as evidence to establish the condition of the chloro- 

 phyll in the leaf. For many years this has been a question of much dis- 

 pute,^^ it being variously claimed that the chlorophyll was present in the 

 chloroplast in the solid condition, that the chlorophyll was in the color- 

 less stroma, that it was adsorbed on the surface of the stroma, that it 

 was dissolved in an oil and that it was combined with lipoidal substances 

 of the chloroplast. Lubimenko ^^ was of the opinion that the chlorophyll 

 is chemically combined with the protein in the chloroplast. It is now 

 realized that some of these assumptions are improbable. Iwanowski ^^ 

 compared the absorption spectrum of leaves with that of colloidal solu- 

 tions and found that the two are similar but not identical. The absorp- 

 tion spectrum of a colloidal solution lies between that of the leaf and 

 that of a true solution of chlorophyll. He states that he was able to 

 reproduce the si^ectrum of a leaf by adding an electrolyte to a colloidal 

 solution of chlorophyll, ^^'ith increasing size of the chlorophyll particles 



"Arnaud, Compt. rend., 100, 751 (1885). Tswett, Tvd. Obsc. jest Kasait., 35, 

 86 (1901) (Russian). Palladin, Ber. hot. Ges.. 28, 120 (1910) ; Biochem. Zeit.. 26, 

 357 (1910). Lommel, Pogq. Ann., 143, 656 (1871). 



"Lubimenko, Compt. rend., 173, 365 (1921). 



"Iwanowski, Ber. bot. Ges., 25, 416 (1907) ; Biochem. Zeit., 48, 328 (1913). 



