CHLOROPHYLL FORMATION 



407 



affected by genetic factors. The protochlorophyll content of several 

 chlorophyll-deficient mutants of corn was found to vary considerably in 

 relation to the protochlorophyll content of their normal sibs, as reference 



Table 7-3. Comparison of Various Dark-grown Corn Mutants with 

 Their Dark-grown Normal Sibs Relative to Protochlorophyll Content 



(Koski, 1949.) 



120 



to Table 7-3 shows. One result in this table which is very striking is 

 the large protochlorophyll content of white seedling-3 — an albino mutant 

 of corn — which is greater than that of 

 its normal sib. All the other chloro- 

 phyll-deficient mutants studied con- 

 tained less protochlorophyll than their 

 normal sibs. 



Photochemical Transformation of Pro- 

 tochlorophyll to Chlorophyll a. Liro 

 (1908) pointed out that greening and 

 chlorophyll formation are clearly dif- 

 ferentiated. Although greening is the 

 result of chlorophyll formation, chloro- 

 phyll formation may take place with- 

 out the plant becoming green. This 

 section will be limited largely to a dis- 

 cussion of the formation of chlorophyll 

 by the transformation of protochloro- 

 phyll in the living leaf. 



When etiolated seedlings are illumi- 

 nated, they first form only chlorophyll a 

 (Seybold and Egle, 1938; Goodwin 



and Owens, 1947;Smith, 1949b ;Blaauw-Jansen et al, 1950;Seybold, 1948- 

 1949). (This is evidence against the existence of protochlorophyll b in 

 etiolated leaves.) Illumination at 0°C produces only a limited amount of 

 chlorophyll. This hmit is reached in a very short time. Continued illu- 



ID 20 30 40 



TIME ILLUMINATED, hr 



Fig. 7-8. Changes brought about in 

 the content of total ether-soluble 

 magnesium and chlorophyll mag- 

 nesium by illumination of dark- 

 grown barley leaves at 0°C. (Smith, 

 1949a.) 



