CHLOROPHYLL AND CHLOROPHYLL DEVELOPMENT 1095 



Jiust how light may function in chlorophyll formation is a problem of 

 great complexity. Preisser (56) investigated the formation of chlorophyll 

 in etiolated plants and believed the leaf green to be formed by the oxida- 

 tion of a colorless compound. He describes his results as follows: 

 "Green leaves were ground in a porcelain mortar. The green fluid 

 obtained by this process was treated with a little lead hydroxide after 

 the filtration. This completely precipitated the green matter. The 

 lead compound was decomposed with hydrogen sulfide. The filtered 

 liquid was colorless. I put it with a little oxygen gas under a mercury 

 receiver. After several days a part of the gas was absorbed, the liquid 

 had become green and flakes of still darker green had deposited. The 

 absorption took place especially under the influence of sunlight." Sachs 

 (61) discusses this question of chlorophyll formation under 11 headings, 

 the most pertinent ones to our discussion being: 



"Leaf green is formed from a substance which is still colorless and which requires 

 only a very small change in order to become green." 



"The formation of this chromogen or leucophyll takes place in most cases simul- 

 taneously with the decomposition of the plasma in the grains, frequently, also, 

 earlier." 



"The leucophyll passes over into chlorophyll bj"^ the action of oxygen in the 

 nascent state or generally by means of very active oxj'gen, probably because a part 

 of the hydrogen is thereby taken away from the leucophyll." 



"In nearly all cases this oxidation takes place if, under the influence of sunlight, 

 oxygen from other compounds becomes free within the cells." 



"The oxidation of the leucophyll to chlorophyll can also take place without the 

 direct influence of light when very active oxygen diffuses to unlighted parts (chloro- 

 phyll in the wood) or when certain substances in the cells (fats and ethereal oils) have 

 the property of ozonizing the oxygen (chlorophyll in the embryo of the pine)." 



Monteverde (44) has studied the origin of chlorophyll in the etiolated 

 plant when exposed to light. He found in etiolated leaves a substance 

 which, under the influence of light, is replaced by chlorophyll; and he 

 called this "protochlorophyll." This substance varies in its absorption 

 spectrum and other properties from Timiriazeff's (77) protophyllin 

 obtained by artificial reduction of the green coloring matter. Monte- 

 verde used wheat, maize, and sunflower, extracting protochlorophyll 

 and yellow pigments with 95 per cent alcohol. This extract when 

 studied spectroscopically gave absorption bands as indicated below. 



Band I, absorption of the extreme red rays to X6800 A; band II, 

 X6400 to 6200 A; band III, X5890 to 5700 A; end absorption X5350 A. 

 Monteverde considered band II the characteristic protochlorophyll 

 band. Upon exposure of the etiolated leaves of wheat to diffuse light 

 for 5 sec. with subsequent alcoholic extraction in the dark, band I of 

 chlorophyll appeared, but weak in intensity. After exposure for 15 sec, 

 the relative inten.sities of the bands were II a, I, III. After an exposure 

 of 1 min., to diffuse light, band I was of greater intensity than II a. 



