Dwarfing Genes in Zea mays and Relation to Gibberellins 497 



2.4 



S 

 S 



tn 



I 

 I- 

 < 2.2 



UJ 



X 



(/) 



< 



UJ 



T3 



c 

 CM 



2.0 



o 



z 



UJ 



o 

 o 



o 

 Normal 



^ 





y^ 



^ 



1.6 I ^ L 



0.01 0.1 I 10 



DOSAGE, /xG 



Fig. 6. Quantitative bioassays for gibberellic acid and bean factor II using nor- 

 mal and dwarf I seedlings. Each point represents the average of ten measurements 

 of the sums of the first and second leaf sheaths. 



assay (13). Experiments reported here with the mutant dg for bio- 

 assay show the presence of gibberellin-like substances from seedling 

 shoots of normal Zea mays, their absence, or presence in reduced 

 amounts, from the mutants d^, do, dg, d^, and an-,^. 



Both normal and mutant seedlings were grown in the greenhouse 

 for periods ranging from 2 to 6 weeks. Five hundred gram samples 

 of the shoots were harvested and stored at — 20° C. Acetone-water 

 extracts were obtained from duplicate samples of each type of ma- 

 terial and purified according to methods developed by West (16, 17). 

 Silicic acid chromatography (16) was used as the final step of purifica- 

 tion for one sample, paper chromatography was used as the final step 

 of purification for the second sample. Each fraction obtained from 

 elution of the columns and from elution of the chromatograms was 

 assayed for the presence of gibberellin-like substances. Evidence for 

 activity was based on the qualitative use of the dr^ bioassay. As a 

 measure of the total response from any one extract, the response data 

 for all active fractions from any one extraction were added together. 



