492 



B. (). Phinney 



gibberelllc 

 acld(0.lwg.) 



dwarf-2 



Fig. 2. Response of the first leaf sheath of tlie mutant, dwarf 2, to a single ap- 

 plication of gibberellic acid. Plants photographed 5 days following treatment. 



sponse to three of the five; still others that produce a growth re- 

 sponse to two of the five, etc. In this way the order of the dwarfing 

 genes in blocking intermediate steps in the gibberellin j)athway 

 would be established. 



(2) Any gibberellin found to be active in promoting the growth 

 of a dwarf mutant should produce less growth when applied to 

 normal plants, if native gibbcrellins are the limiting factor distin- 

 guishing the two types of growth. Also, gibbcrellins producing a dif- 

 ferential response for a mutant should not produce a differential re- 

 sponse when applied to normal plants. This would be expected since 

 the normal form of each dwarfing gene would presumably be able to 

 carry out its function of converting a particular intermediate to the 

 next step leading to a final gibberellin product necessary for growtli. 



(3) Gibberellins should be present in normal plants and absent, 

 or present in reduced amounts, in the dwarf seedlings. However, the 



