580 T. Hayashi 



The C02-fixation activity for whole plants was measured using 

 a Yamada-Murata apparatus (7) in the open field. Potted plants were 

 introduced into a chamber which consisted of a wooden frame cov- 

 ered with transparent sheets. Air was forced into this chamber by 

 an electric blower. Both the air leaving the chamber and the air from 

 outside were bubbled through aqueous NaOH solutions, and the 

 amount of COo fixed by the plants was calculated from the differ- 

 ence between the alkalinities of the two NaOH solutions. 



For determination of fixation by attached leaves a tomato leaf at- 

 tached to an intact plant was placed into a transparent chamber made 

 of polyacryl resin. The CO^-fixation activity was measured in the 

 same manner as for the whole plants in the open field. 



Leaf area was measured by w^eighing blue-print paper pieces 

 trimmed accurately to the shape of the leaf. 



Dry weight w^as determined by drying samples at 90° C. for one 

 hr., then at 70° C. until constant weight was attained. 



For the determination of sugar content, samples were pulverized 

 to pass through an 80 mesh sieve A 500 mg. portion of the powder was 

 then extracted with 80 per cent ethanol, and the amount of reducing 

 sugar in the extract was determined by the Somogyi method (6). Total 

 sugar was determined after hydrolyzing the saine extract with 2 per 

 cent H-.S04 for 15 min. Starch was estimated in the residue from the 

 ethanol extract by the method of Pucher et al. (5). 



RESULTS 



Effect of GA Treatment on Photosynthetic Activity of Whole Plant 



Changes in the height of tomato plants treated with GA are shown 

 in Figure 1. In both control and treated plants each circle represents 

 the mean value of ten determinations. 



Five tomato plants were introduced into the large chamber men- 

 tioned above, and their photosynthetic activity was determined in the 

 open field. Two chambers with five plants each were used for the con- 

 trol, and two chambers with five plants each were used for treatment. 



The curves showing the photosynthetic activity (the amounts of 

 CO2 fixed) versus the horizontal intensity of illumination for the 

 plants 8 days after the start of the treatment arc given in Figure 2. 

 The changes in the photosynthetic activity during the 8 day period 

 following the treatment at 20,000 lux and 60,000 lux are also given 

 in the same figure. The photosynthetic activity of ^\•hole tomato plants 

 was increased about 18 per cent by the GA treatment. 



In rice plants, the increase in height, especially the elongation of 

 the leaf sheath, was appreciable. Three rice plants were cultined in 



