Growth Factors in Tomato Fruit 



697 



total weight of juice equal to the initial weight of the tomatoes. The 

 pH of this juice was generally around 4.0. 



Separation of the Stimulating and Inhibiting Principles 



A difficulty arose from the fact that both the growth-promoting 

 principle and the strong inhibitor were generally extracted together. 

 Among the various methods tried to separate them, two techniques 

 gave satisfactory results, namely partitioning between water and ethyl 

 acetate and adsorption on activated charcoal. 



Extraction with ethyl acetate. When the crude juice or an aqueous 

 solution containing the active principles was shaken with ethyl ace- 

 tate, the growth-promoting principle moved, at least in part, to the 

 ethyl acetate layer, the inhibitor remaining in the water layer (25). 

 Experiments showed that more of the growth-promoting factor moved 

 to the ethyl acetate layer at acid pH values (2.0) than at slightly alka- 



_i 

 o 

 q: 

 I- 

 z 

 o 

 o 



200 



X 

 LlI 



X 

 CO 



50 



MhS 



McE 



EA 



Fig. 7. Effects on Helianthus tuberosus cultures obtained from stepwise extraction 

 of lyophilized tomato fruits with the following solvents: P: petroleum ether (b.p. 

 30 to 60° C), B: benzene, EA: ethyl acetate, Mc: cold methanol, Mh: hot methanol, 

 W: hot water. The Mc extract has been partitioned between ether (McE) and 

 water (McW) under acid conditions. The Mh extract, upon concentration and 

 standing in the cold, has separated into a white precipitate (Mhp) and the su- 

 pernatant (MhS). All fractions were tested on Helianthus tuberosus, strain P-17, 

 at concentrations equivalent to 20 per cent (v/v) of the original juice. Each value is 

 the average of 12 replicate cultures. Differences less than 15 per cent are not statis- 

 tically significant. 



