174 PLANT GROWTH SUBSTANCES 



fruits sprayed with /3-naphthoxyacetic acid. Hollow fruits sometimes 

 occurred in the sprayed fruit, but occasionally these were also found in 

 the pollinated ones. Young fruits were prepared for a study of the mineral 

 residue in sprayed and pollinated fruits. After microincineration the 

 ash residue in the sprayed and pollinated fruits were compared. There 

 was a Hke mineral pattern in both sprayed and unsprayed fruits which 

 agrees with reports made by others that the mineral composition as 

 shown by analysis is similar when fruits are set either by pollen or with 

 chemicals. 



Alpha-naphthaleneacetic acid is used to thin apple blossoms and also 

 to delay or prevent fruit-dropping at harvest time. The question was 

 raised as to how this growth substance could have seemingly opposite 

 effects. An investigation now under way shows that it has but the one 

 effect of delaying dropping of fruit. The thinning of blossoms is the 

 result of heavy nutritional dropping following heavier early sets induced 

 by a-naphthaleneacetic acid. Therefore, the final result is fewer fruits 

 when the acid is applied at the blossoming stage. 



REFERENCES 



1. Eames, a. J., Science, 110:235 (1949). 



2. Fifth Annual North Central Weed Conference Research Report. Project I. 



Use of herbicides in control of perennial herbaceous weeds. December, 

 1948. Springfield, Illinois. 



3. Gardner, F. E., Marth, P. C, and Batzer, L. P., Proc. Amer. Sac. Hort. 



Sci., 37:415 (1940). 



4. Mitchell, John W., Botan. Gaz., 101:688 (1940). 



5. Murray, Mary A. and Whiting, A. Geraldine, ibid., 110:404 (1949). 



6. Proc. Fourth Annual Meeting of the North Central Weed Control Conference 



and Report of Research Committees. December, 1947. Topeka, Kansas. 

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7. Roberts, R. H., and Struckmeyer, B. Esther, Proc. Amer. Soc. Hort. 



Sci., 44:417 (1944). 



8. Stebbins, T. C., Neal, A. L., and Gardner, V. R., ibid., 48:63 (1946). 



9. Swanson, Carl P., Botan. Gaz., 107:522 (1946). 



10. Zimmerman, P. W. and Hitchcock, A. E., Ann. Rev. Biochem., 17:601 

 (1948). 



