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M. J. Bukovac and S. H. IVittwer 



COMPARATIVE BIOLOGICAL ACTIVITIES OF 

 GIBBERELLINS Ai, A2, A3, AND A4 

 Vegetative Extension 



Epicotyl elongation in beans (Phaseolus vulgaris, 'Blue Lake'). Bean 

 seedlings were germinated in quartz sand, and transferred to aerated 

 solution cultures containing a complete nutrient solution when the 

 primary leaves were approximately 50 per cent expanded (4). After 

 24 hrs. 10 lA. of a 3 X lO-^, 3 X 10% or 3 X 10-^ M solution of gib- 

 berellins Aj, A2, A3, or Aj (Table 1) were applied to the terminal 

 bud (Figure 1) or to the upper surface near the base of one of the 

 primary leaf blades. Epicotyl elongation was determined 48 or 96 

 hours following treatment. 



Application of gibberellin Aj or A3 to the leaf blades resulted in 

 plants with significantly longer epicotyls than plants similarly treated 

 with A2 or A4 (Figure 2 and Table 2). Length of epicotyls of plants 

 treated with gibberellin Ao on the leaf blades did not differ signifi- 

 cantly from the controls. All gibberellins when applied to the terminal 

 bud resulted in plants with epicotyls that were significantly longer 

 than those on the controls. Gibberellins A^, A3, and A4, however, 

 were slightly more effective than Ao (Table 2). This same relationship 

 held for all three concentrations of the various gibberellin solutions. 

 Petiole elongation in celery (Apiurn graveolens, 'Utah 10-B'). 

 Seedlings were started in sand, selected for uniformity of fresh weight 

 and petiole length, and transferred to solution cultures at the three to 

 four true leaf stage. Ten jxl. of a 3 X 10^ or 3 X 10^^ M solution of 

 gibberellins A^, Ao, A3, or A4 were applied to the youngest unfolding 

 leaf 96 hrs. after transfer of the plants to solution cultures. The length 

 of the second outer petiole was recorded 14 days later. Treatment 



Tabic 1 . Characteristics of the gibberellins assayed. 



Decomposition. 



