582 T. Hayashi 



Table 1 . Effect of treatment with gibberellic acid 

 upon leaf area. 



500 ml. glass jars by the water culture method. Ten jars were intro- 

 duced into the large chamber for measurement of photosynthetic ac- 

 tivity. As with tomato plants, two chambers were used for the con- 

 trol and treatment for each experiment. The curves of the CO2- 

 fixation activity versus the horizontal intensity of illumination for 

 the plants 7 days after treatment are shown in Figure 3. The figure 

 shows that the activity was increased about 10 per cent by the GA 

 treatment. 



The dry weight of both control and treated plants is shown in 

 Figure 4. These are the data for the 8th day after the start of the 

 treatment with the tomato plants, and for the 7th day with the rice 

 plants. As a result of the GA treatment in the tomato plant, the dry 

 weight of all parts increased; in the rice plant, the dry weights of the 

 leaf, sheath, and stem increased, while the dry weight of the root de- 

 creased. Table 1 shows the effect of GA treatment upon leaf area. 



Effect of GA Treatment on Photosynthetic Activity of 

 Attached Leaves 



The change in the photosynthetic activity of attached leaves was 

 studied following the growth of the same leaves. The activity of 

 young and adult leaves is shown in Table 2 in Avhich the activity is 

 expressed by the amounts of CO2 fixed per unit leaf area. The young 



Table 2. Effect of treatment with gibberellic acid on CO2 

 fixation by attached leaves. 



