602 



J. Kato 



Table 1. Differences in activities of gibberellin 

 and auxin (11, 12). 



Elongation of etiolated pea stem sections showed that the effect of 

 GAi was additive to the effect of 0.0001 mg/1 through 10 mg/1 of the 

 auxins (12). Purves and Hillman (23) obtained similar results. Even 

 when auxin inhibited the shoot growth of cucumber seedlings by 

 being supraoptimal in concentration, GA^ added to the auxin solu- 

 tions manifested its own growth-promoting effect independent of the 

 auxin effect (Table 2). As to the root growth of cucumber seedlings, 

 GAj showed no effect; and GA^ with auxin inhibited growth. Inhi- 

 bition by NAA of the lateral bud of kidney bean was reversed com- 

 pletely by 5 per cent GA^-lanolin paste. GA^ is inhibitory to root 

 formation and is antagonistic to the root-forming activity of lAA. 

 All these results show that gibberellin works quite differently from 

 auxin. The inhibition of shoot growth by coumarin (CM) and 

 maleic hydrazide (MH) was reversed by GA^ (Table 2) and the inhi- 

 bition of root growth by CM and MH was not reversed, nor increased 

 (Table 3). Hence gibberellin differs also from these substances in its 

 physiological action. 



In order further to confirm that the reaction sequence caused by 

 gibberellin is different from that caused by auxin, the effect of GA 

 was observed in combination with various types of anti-auxins. As 

 shown in Figures 1, 2, 3, and 4, 4-chlorophenoxyisobutyric acid 



Table 2. Effect of gibberellin A on lAA-induced growth inhibition of cucumber 

 seedling (11). 



level 



* In each column, differences among the values arc not significant at the 5 per cent 



t In each column, differences among the values are significant at the 5 per cent level. 



