496 B. O. Phinney 



Table 1 . Relative activities of the gibberellins, GAi, GA2, 

 GA3, and BF-II for the mutants dwarf 1, 2, 3, and 5 of Z.ea mays. 



* From one bioassay run at one dosage level, the relative 

 activities of the gibberellins for the mutant, anther ear-\, were 

 very similar to those for the mutant, df,. 



t Each value is the average from four quantitative bioassays, 

 each assay run at three dosage levels. 



to sets of ten seedlings at one dosage level for the mutant an^. Gib- 

 berellin Aj, GAo, and GA3 show an order of activity of GA3 > GA^ > 

 GA2 for all five mutants. Preliminary experiments suggest that GA4 

 is intermediate in activity between GA3 and GA^. In contrast to the 

 similar order of activities of these gibberellins for the GAg-responding 

 mutants, bean factor II is 5 per cent as active as GA3 for the mutant 

 di (Figure 6); it is as active or more active than GA3 for the mutants 

 ^2, d^, d^, and an-^. At dosage levels of 0.1 /xg/plant, BF-II produces 

 no growth response for the mutant d-^, and a normal type growth re- 

 sponse for the other four GA3-responding mutants. 



Relative Activities of the Gibberellins for Normal Zea mays 



The relative activities of the gibberellins GA^, GAo, GA3, and 

 BF-II have been determined using normal Zea mays seedlings for bio- 

 assay. The seedlings were treated and measured in the same manner 

 as described for the quantitative use of the dwarf bioassay. GA3 and 

 BF-II were applied at three dosage levels, GAj and GAo at only one 

 dosage level. The activities of GA3 and BF-II were found to be very 

 similar to each other (Figure 6). Comparison of dosage-response 

 curves suggests that the order of one hundred times as much GA3 is 

 necessary for an initial growth response for normal seedlings as com- 

 pared to the GAg-responding dwarf seedlings. Gibbcrellin A^ and 

 GAo were also found to produce a smaller growth response for normal 

 seedlings than for the dwarf mutants. The order of activity for normal 

 seedlings of Zea mays appears to be GA3 = BF-II > GA^ > GA2. 



Gibberellin-Like Su])stances From Zea mays 



Gibberellin-like substances have previously been reported from 

 immature normal kernels of Zea mays using the mutant d^ for bio- 



