JIRO KATQi 



Kyoto University 



Physiological Action of GibbereUin With 



Special Reference to Auxin 



Since Yabuta et al. (31) isolated gibberellins from the culture medium 

 of Gibberella fiijikuroi (Saw) Wollenweber, it has been observed that 

 gibberellin has the effect of causing hyperelongation in many higher 

 plants. I became interested in the mode of action of gibberellin and 

 began a study comparing it with auxin. 



At the start I had to use a crude preparation of gibberellin. How- 

 ever, it became evident that gibberellin is a growth substance quite 

 different from auxin. As summarized in Table 1, gibberellin was 

 negative in the Avena test and in the pea test at any concentration 

 up to 1,000 mg/1. A 1 per cent lanolin paste of gibberellin did not 

 inhibit, but accelerated, the growth of lateral buds of kidney bean 

 and of etiolated pea seedlings. Gibberellin was not active in induc- 

 ing callus formation on the cut surface of tomato and sunflower seed- 

 lings. Gibberellin A (GA^) did not promote the root formation of 

 etiolated pea stem, but was rather inhibiting (Table 1). 



The root growth of cucumber seedlings was not affected by from 

 1 to 100 mg/1 of GAj. This agrees with the result of Brian et al. (5). 

 Whaley and Kephart (28) have reported that the root growth is sig- 

 nificantly stimulated by gibberellic acid (GA) in a certain genotype 

 (strain 854) of maize but not in another (strain 857). These results 

 led to the conclusion that gibberellin is a type of growth-regulating 

 substance quite different from auxins as represented by indole-3-acetic 

 acid (lAA) (11, 12). 



In order to confirm this conclusion, the interaction between gib- 

 berellin and auxin was studied. Ten mg/1 of GA^ were added to a 

 concentration series of lAA and 1-naphthaleneacetic acid (NAA). 



^Subsequently: Division of Biology, California Institute of Technology, Pasa- 

 dena, California. 



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