400 Mineral Nutrition of Plants 



i). Thus, there appears to be a mobilization of magnesium and phos- 

 phorus into leaves of greening barley seedlings and an increase in ether- 

 soluble organic materials. Smith concludes that, in view of the relatively 

 low concentration of protochlorophyll attained under equilibrium con- 

 ditions in the dark, chlorophyll synthesis must be a rather complex 

 series of reactions involving protochlorophyll synthesis with chlorophyll 



Chlorophyll x/0 { 



Et sol. Material x!0 i 



G Ash, xlO' 



Ma - Chi a 10 7 

 P-Et sol. rIO 7 



30 to SO 60 



IRRADIATION TIME -HOURS. 



Figure i. Effect of light on chlorophyll and other associated constituents 

 of dark-grown barley leaves on intact plants. — }. H. C. Smith (47). 



Composition given for chlorophyll, total ether-soluble material, chloro- 

 phyll magnesium, ether-soluble phosphorus, and total ash. 



synthesis and the mobilization of magnesium and phosphorus into the 

 synthesizing system. The significance of the accompanying increase of 

 ether-extractable phosphorus is not clear, but phosphorylations may be 

 involved. This increase is in harmony with Stoklasa's (5/) original 

 discovery that seedlings germinating in the light contain more ether- 

 soluble and alcohol-soluble phosphorus than dark-grown plants. 



These results on the magnesium and phosphorus mobilization and 

 conversion into ether-soluble compounds during chlorophyll synthesis 



