Effect of Gibberellin on Photosynthesis 587 



Next, referring to the carbohydrates produced, the dry weight in 

 the top increases, while in the root it decreases by the GA treatment 

 as given in Figures 4 and 5. 



Brian also recognized the growth inhibition of roots when GA 

 was added to the culture solution. He considers this to be due to the 

 direct action on roots of GA in a high concentration. 



Since the data given in Figures 6 and 7 represent only the steady 

 state of the contents of sugars and starch, it is rather difficult to ex- 

 plain inclusively all these facts. Even if the photosynthetic activity 

 does increase, the content of such carbohydrates does not necessarily 

 increase. Any decrease in these carbohydrates may have resulted from 

 the increase in the activity of the system utilizing the photosynthetic 

 products. 



The increase of reducing sugar in GA-treated plants corresponds 

 with the increase in the invertase activity which has been described 

 in a previous report (3). The decrease of starch, on the other hand, 

 does not correspond with the decrease in the activity of amylase 

 which has also been described in that report. More studies are re- 

 quired to clarify these observations. 



LITERATURE CITED 



1. Brian, P. W., Elson, G. W., Hemming, H. G., and Radley, M. The plant-growth 

 promoting properties of gibberellic acid, a metabolic product of the fungus 

 Gibberella fujikuroi. Jour. Sci. Food Agr. 5: 602-612. 1954. 



2. Haber, A. H., and Tolbert, N. E. Photosynthesis in gibberellin-treated leaves. 

 Plant Physiol. 32: 152, 153. 1957. 



3. Hayashi, T., Murakami, Y., and Matsunaka, S. Biochemical studies on bakanae 

 fungus. XXXVI. The physiological action of gibberellin. 8. Changes in the 

 activities of various enzymes in leaf-sheaths of rice plants treated with gibberel- 

 lin. Bui. Agr. Chem. Soc. Japan. 20: 159-164. 1956. 



4. Noggle, G. R. A study of the effect of gibberellic acid on the alcohol-soluble 

 constituents of oats. Proc. 55th Ann. Convention Assoc. So. Agr. Workers. 55: 

 228, 229. 1958. 



5. Pucher, G. W., Leavenworth, C. S., and Vickery, H. B. Determination of starch 

 in plant tissues. Analyt. Chem. 20: 850-853. 1948. 



6. Somogyi, M. A new reagent for the determination of sugars. Jour. Biol. Chem. 

 160: 61-68. 1945. 



7. Yamada, N. et al. A removable apparatus for measuring photosynthesis. Agr. 

 Hort. Tokyo. 30: 73, 74. 1955. 



DISCUSSION 



Dr. Tolbert: Dr. Haber and I have confirmed these results work- 

 ing with other plants. We found that radioactive COo fixation per 



