Growth Factors in Tomato Fruit 



695 



Table 1 . A comparison between the effects of tomato juice and coconut miliv upon 

 the increase in fresh weight of various tissue cultures. 



CHEMICAL WORK 



Bioassays 



To measure the biological activity of the different fractions which 

 have been isolated, the following two assays were used: 



The Jerusalem artichoke test. The difficulty of securing large 

 quantities of crown-gall tissue which would be homogeneous prompted 

 us to use the xylem parenchyma of tubers of the P-17 strain of Je- 

 rusalem artichoke {Helianthiis tuberosus) with which we had worked 

 previously (27, 28). According to the procedure outlined (27), cylin- 

 ders of tissue, generally 15 mg. in fresh weight, were removed asep- 

 tically from the tubers and planted on sterile media. The increase in 

 fresh weight of the cultures was determined 21 days later. 



The basal medium contained the following substances: the min- 

 eral salts of the N^ solution (27) or those of an N2 solution which had 

 the same composition as the Nj one, except that the sodium diphos- 

 phate had been replaced by an equivalent amount of commercial 

 sodium hexametaphosphate (Calgon); sucrose (50 g/1); lAA (5 X ^^'^ 

 M); and Difco Bacto agar (10 g/1). The pH was always adjusted to 

 5.5 with HCl or NaOH before autoclaving. The media were auto- 

 claved for 15 to 20 min. at 15 lbs. pressure. 



The auxin was added to the medium routinely because (a) Je- 

 rusalem artichoke tuber tissues need an auxin in order to proliferate, 

 (b) the aim was to pick up substances other than auxins, and (c) 

 the factors present in TJ seemed to have a synergistic effect with 

 auxins. 



