JOHN W. MITCHELL 149 



fell below that of untreated ones (38,50,51). The net result was a 

 depletion of the readily available carbohydrates in leaf tissues. Phenyl- 

 acetic acid did not accelerate starch degradation in leaves nor did 

 naphthaleneacetamide. The effect of such growth-regulating substances 

 as indoleacetic acid and 2,4-D on reserve carbohydrates in other parts 

 of plants is similar to that described for leaves (1,2,6,34,46,50,56). 



Bausor (2) obtained evidence that tomato cuttings retained their 

 starch reserves when kept in darkness and supplied with sugar. Treated 

 plants, on the other hand, utilized their starch reserves irrespective of 

 the external carbohydrate supply. In these same experiments 0.02 per 

 cent indoleacetic acid inhibited starch digestion in thin stem sections 

 but hastened starch digestion in intact stems. This behavior may be 

 explained, however, on the basis of the magnitude of treatment, there 

 being much more growth regulator applied per cell in the case of the 

 sections than in the case of the entire stems. 



Hydrolysis of complex carbohydrates, such as hemicelluloses, may 

 also be accelerated by the apphcation of 2,4-D to plants (9). Thus, the 

 action of some hydrolytic enzymes in plants is either directly or in- 

 directly accelerated by some kinds of growth regulators. 



Hagen et al. (19), on the other hand, have recently shown that the 

 activity of castor bean lipase in hydrolyzing olive oil was less in the 

 presence of small amounts of 2,4-D acid than when used alone. They 

 believe that only the acid form of 2,4-D was directly effective in reducing 

 the lipase activity under their test conditions. Some hydrolytic enzymes, 

 therefore, may under some circumstances be inhibited by the presence 

 of a chemical such as 2,4-D. 



Nitrogenous compounds in plants are also affected by the application 

 of growth substances. In general most growth-modifying chemicals bring 

 about an increase in protein and amino acid content of stems when the 

 regulator is appHed in relatively large amounts (31,41,42,49). In succulent 

 plants regulating chemicals generally cause a mobilization of nitrogenous 

 constituents towards the basal parts of the stems, both in cuttings and 

 intact plants (2,42,52,55). This is not true, however, of all regulating 

 chemicals. Applied to bean plants, for instance, naphthaleneacetic acid 

 brought about a twelvefold increase in water-soluble nitrogenous com- 

 pounds in the stems. Naphthaleneacetamide, on the other hand, brought 

 about a decrease in amount of these compounds in the stems (31). 

 Similar differences were also observed in carbohydrate fractions when 



