508 



A/, y. Bukovac and S. H. Wittwer 



Fig. 2. Growtli ol l)eaii epicotyls following application of 10 ^1. of 3 x 10 ■ M 

 solution of gibbcrellins Aj, A., A:i, or A4 to one of the primary leaf blades (top), or 

 10 the terminal biul (bottom). Left to right: control, Aj, A,, A3, and A4 (photo- 

 graphed 96 hrs. after treatment). 



with 3 X 10--^ M of Aj, A3, or A4 produced plants with significantly 

 longer petioles than nontreated controls. Plants treated with A, did 

 not differ from the controls. Petiole elongation was equally stimu- 

 lated by Aj and A.^ at 3 X 10 "' ^^> ^"<1 signifuantly more so than 

 with Ao and A4 (Table 2). 



Stem elongation in cucumber (Cucutnis sativiis, 'Burpee Hybrid'). 

 Cucumber seeds were germinated in vermiculite and transplanted into 

 soil after the cotyledons had emerged. Twenty-four hours later, a ten 

 ,A. aliquot of a 3 X 10 •"'. 3 X 10 *, or 3 X 10"^ M solution of gib- 

 berellin A^, A2, A3, or A4 was aj)plied to the terminal bud. At all con- 

 centrations, A4 was strikingly more effective than A,, Ao, or A.5 in 

 stimulating stem elongation (Table 2). The comparative stem elonga- 

 tion of the 'Burpee Hybrid' cucumber and 'Blue Lake" bean following 

 application of various amoimts of gibbcrellins A., and .\j to the 

 terminal bud is illustrated in Figure 3. 



