Growth Factors in Tomato Fruit 



693 



2 4 8 16 



CONCENTRATION (% ,V/V ) 



Fig. 4. Effect of various concentrations of tomato juice (TJ) and coconut milk (CM) 

 on tfie growtli of cultures of Helianthus tuberosus tuber tissues, 'Blanc commun' 

 in the presence of lAA (1 mg/1). (Curve TJ from 24, curve CM, new data.) 



Necessity of an Auxin 



As a matter of fact, there seems to be a synergistic effect between 

 auxins and TJ (Figure 3). This effect became very striking when 

 various fractions were bioassayed (Figures 5 and 6). 



Comparison With Coconut Milk 



Tomato juice often produced a larger increase in fresh weight of 

 various cultures than did a comparable concentration of coconut 

 milk, as is shown in Table 1 and in Figure 4. With coconut milk, 

 however, the cultures were generally more compact and healthier 

 than with TJ. 



Presence of an Inhibitory Principle 



Often, however, the tomato juice became highly inhibitory, 

 whereas coconut milk did not. In cultures of Morel's normal strain 

 of Parthenocissus tricuspidata, for example, the toxic effects of TJ 

 became evident as soon as the TJ concentration was increased above 

 5 per cent (v/v), whereas coconut milk promoted growth over that of 

 the controls even at a 50 per cent concentration (3). Thus, it soon 

 appeared that, in addition to growth-promoting factors, TJ also con- 

 tained substances inhibitory to growth in tissue cultures and to a 

 much greater degree than coconut milk. 



