584 



T. Hayashi 



>- 

 cr 

 o 



ROOT 



• O A Control 

 0» i GA-treoted 



2 4 6 8 



DAYS AFTER TREATMENT 

 Fig. 5. Changes in dry \veight after treatment with gibberellin. 



10 



leaves were those which were growing vigorously during the experi- 

 ment, and the adult leaves were those which had already attained the 

 maximum leaf area at the start of the experiment. The difference be- 

 tween young and adult leaves was practically two leaf ages. The table 

 shows that there is no significant difference in the photosynthetic ac- 

 tivity between the control and the treated plants. It seems, therefore, 

 that GA does not affect the photosynthetic activity on a unit leaf 

 area basis. 



Changes in Content of Sugars and Starch by GA Treatment 



Only rice plants were used for this experiment. Cultural conditions 

 were the same as in the measurement of the photosynthetic activity. 

 The effects of GA treatment on the morphology of rice plants are 

 remarkable. For example, elongation of the leaf sheath of the youngest 

 leaf during 9 days was 1.2 cm. in the control, while it was 16.5 cm. in 

 the treated plants. 



Changes in dry weight are shown in Figure 5. The dry weight of 

 the top increased, but that of the root decreased, as the result of the 

 GA treatment. In total, dry weight was increased by the treatment. 



Changes in the content of sugars are shown in Figure 6. In this 

 figure, the scale for the root is magnified five times relative to that 

 for the top. At the start of the treatment, the sugar content was very 

 low owing probably to the after-effect of transferring plants from soil 

 ciUture to water culture. Four days after the treatment, the content 



