Miscellaneous Uses 



301 



There are several cases in agriculture where a reduction of apical 

 dominance is desirable. In these cases the apical bud is often mechani- 

 cally broken off to force branching. This cultural practice is spoken 

 of as pinching. 



That antagonists of auxins could bring about the same loss of 

 apical dominance and the same degree of branching as pinching has 

 been demonstrated by Beach and Leopold (195^). Their data in 

 figure 124 demonstrate that maleic hydrazide in concentrations of 

 600 or 1000 mg./l. resulted in as much branching of chrysanthemums 

 as did pinching. No loss in quality of the flower was encountered. In 

 a similar manner ethylene and TIBA (2,3,5-triiodobenzoic acid) have 

 been found to encourage basal shoots of roses (Asen and Hamner, 

 1953). 



In the commercial production of tobacco the flowering tips are 

 removed from the plants some time before harvest, because the flowers 

 adversely affect the leaf quality. When the tips are removed, apical 



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 CL 



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CONC. OF MALEIC HYDRAZIDE 



Fig. 124. The removal of apical dominance in three varieties of chrysanthemum 

 by foliar applications of maleic hydrazide as compared with pinching (manual 

 removal of the apical bud). Concentrations of maleic hydrazide expressed in 

 mg./l. (Beach and Leopold, 1953). 



