A. E. MURNEEK 343 



period, growth regulators have been found effective tools in the control 

 of development of certain tissues and organs. Their practical application, 

 in several instances, has outrun our present scientific knowledge. As a 

 result of further experimental work additional and even greater usefulness 

 undoubtedly will be found for these catalytic substances in seed and 

 fruit production. Progress in this field certainly would be hastened if 

 more information were available on the detailed physiology of plant 

 reproduction, with particular reference to the crucial phases. 



Heretofore the main emphasis in analyses of sexual reproduction has 

 been placed on the embryo and mechanisms leading to its formation 

 and growth. Attention is now being called to the importance of the 

 endosperm and associated tissues in seed and fruit development. 



Information has been presented which shows how the same synthetic 

 growth regulator (naphthaleneacetic acid) may have quite opposite 

 effects in sexual reproduction, depending on the concentration used 

 and the time of application especially in relation to seed and fruit 

 development. A relatively weak aqueous solution may initiate flowers, 

 promote fruit set, and retard fruit abscission in some plants, while 

 one of higher concentration will inhibit or delay flower induction, 

 curtail or prevent seed development, stop or retard fruit growth, and 

 cause abscission. 



Though probably of considerable importance in the functional life 

 of plants, only a beginning has been made in studies of the over-all 

 effects on metabolism of certain phases of reproduction, with reference 

 to absorption of soil nutrients, carbohydrate assimilation, and other 

 major plant activities. Hormones of various kinds, undoubtedly, have 

 roles here just as in detailed tissue growth and development. 



REFERENCES 



1. Avery, G. S. et al.. Am. J. Botany, 29:765-772 (1942). 



2. Batjer, L. p. and Thompson, A. H., Proc. Am. Soc. Hort. Sci., 47:35-38 



(1946). 



3. Bauser, S. C, Am. J. Botany, 27:769-779 (1940). 



4. BiDULPH, O. and Brown, D. H., ibid., 32:182-188 (1945). 



5. Block, R., Contrib. Boyce Thomps. Instil., 9:439-454 (1938). 



6. Bonner, J. and Thurlow, J., Botan. Gaz., 101:613-624 (1949), 



7. Bonner, J., ibid., no: 625-627 (1949), 



8. Brink, R. A. and Cooper, D. C, ibid., 102:1-25 (1940). 



9. , Botan. Rev., 13:423-541 (1947). 



10, Britten, E. J., Am. J. Botany, 34:211-218^(1947). 



