Gibberellin- Auxin Interaction and Metabolic Basis 



615 



Table 3. Effect of length of stem through which GA passes on degree of subse- 

 quent synergism with lAA in section growth. 



mm. sections themselves, as in Table 2). One puzzling fact is that no 

 series showed synergism at the 50 mm. length of pretreated stem. 

 We cannot at the moment explain this, but it seems not to obviate 

 the conclusion that in stem tissue from the longer photoperiod 

 plants, which did not show GA-IAA synergism in 5 mm. sections, 

 synergism was obvious in the longest stems treated. These results 

 thus corroborate and extend our previous findings (7). 



The possibility remained that it was the 1 hr. gap in time be- 

 tween GA and lAA treatments, rather than the length of stem, which 

 was responsible for the synergism induced in the previous experiment. 

 This was tested by dipping excised 5 mm. sections from each of the 

 different photoperiod groups into GA-sucrose-buffer or control so- 

 lutions for 1 hr., then transferring them to growth solutions contain- 

 ing or lacking lAA for an additional 17 hrs. The results, shown in 

 Table 4, indicate that the time lapse is not the important factor, in 

 that synergism is clearly manifested once again only in the 8 hr. 

 photoperiod peas. In a subsequent experiment (Table 5) it was found 

 that, in the 8 hr. peas, the growth increments due to GA, as well as 

 the GA-IAA synergism, were induced equally by exposure of the 5 

 mm. sections to 1, 10, or 60 min. of 10-^ M GA. These effects resemble 

 similar ones for lAA already described (6), and indicate that timing of 



