CHLOROPHYLL AND CHLOROPHYLL DEVELOPMENT 1101 



INFLUENCE OF FACTORS OTHER THAN RADIATION ON CHLOROPHYLL 



FORMATION 



While it is hardly within the province of this paper to discuss the 

 effects of various factors other than radiation upon the formation of 

 chlorophyll, it is obviously worth while to include a brief statement 

 of some of the other known factors, supplementary to illumination, 

 influencing chlorophyll development. The extent of the available 

 observations makes it necessary to select only representative instances. 



The production of chlorophyll is affected by temperature, and Wiesner 

 (84), using barley seedlings, gives data which support the conclusion 

 that temperatures somewhat above ordinary room temperature are 

 the most favorable, while with very low or very high temperatures 

 there is no greening. 



Gris (23) noted in 1844 that plants deprived of iron do not normally 

 produce chlorophyll. Emerson (15) cultivated Chlorella in pure cultures 

 using Warburg's medium with glucose. By varying the amounts of 

 iron used in the culture medium the chlorophyll content differed widely. 

 Oddo and PoUacci (50) grew plants of Zea Mays, Solanum nigrum, 

 Datura Stramonium, Euphorbia sp., and Aster sinensis in a standard 

 nutrient solution lacking iron but containing the magnesium salt of 

 pyrrole-a-carboxylic acid, and found chlorophyll formation. Deuber (9) 

 was unable to confirm this work with corn, cowpea, soy bean, and 

 Spirodela. Sideris (68) reported that titanium trichloride could be 

 substituted for iron in the formation of chlorophyll in the growth of 

 pineapples. The chemical form in which the iron is presented to the 

 plant seems to make little difference so long as the pH is kept such 

 that there is a soluble iron compound available at all times. Marsh 

 and Shive (41) studied this problem with soy beans and found that 

 ferric glycerophosphate, soluble ferric phosphate, ferric tartrate, and 

 ferrous tartrate vary in their availability depending on the pH of the 

 media. Hopkins and Wann (28a), using Chlorella, also showed clearly 

 that the availability of the iron for the plant is closely related to the 

 hydrogen ion concentration of the media at the various stages of growth. 

 According to Densch and Hunnius (8), copper may replace the iron at 

 least partially in the chlorophyll synthesis. 



That the absence of necessary mineral salts in the soil results in the 

 diminution of the chlorophyll and carotene contents of the leaves was 

 stated by Ville (80). Maiwald (40) found that the amount of potassium 

 salts used as fertilizer greatly influenced the intensity of the greening 

 in the leaves of the potato. If large amounts of potash were applied, 

 the leaves turned yellow. In 1929 Schertz (64) confirmed these results 

 of Maiwald. Another essential element affecting chlorophyll develop- 

 ment is manganese. McHargue (42) observed that wheat seedlings 

 grown in manganese-free Pfeffer's nutrient salt solution grow normally 



