84 



14 

 The nature of response observed in the C-labeled 2,4-D transloca- 

 tion studies can be partially explained by a recent study by Mulligan 



and Patrick (1979). GAo was shown to promote the transfer of C and 



32 

 P-labeled photosynthates to the site of GA 3 application rather than to 



competing "sinks" such as roots and meristematic tissues. This increase 

 in transfer away from normal "sinks" to the site of GAo application was 

 shown not to be caused by increased photosynthesis rates, increased 

 assimilate export rate from "sources", nor by altering the mobilizing 

 ability of other competing sinks. Mulligan and Patrick (1979) provided 

 evidence that GA 3 was not acting on any transfer process remote from its 

 point of application but was acting locally. A similar relationship in 

 waterhyacinths could account for the suggestion of increased transloca- 

 tion to GA 3 treated petioles in this study. The data also suggested 

 reduced translocation to meristematic sinks in GA 3 treated plants; 

 however, due to variability of the data, significance was not 

 demonstrated consistently. 



The costs analysis of the use of GA3 in conjunction with lower than 

 normal rates of 2,4-D indicates that its use is not justified economi- 

 cally. However, a substantial increase in 2,4-D prices, a reduction in 

 GA3 costs, or a documented environmental concern over the quantity of 

 2,4-D applied to public waters could alter this analysis. Pending the 

 development of more environmentally compatible and efficacous 

 herbicides, the most prudent way to reduce the quantity of 2,4-D used in 

 waterhyacinth control and thus herbicide expenditures is to begin 

 control operations before the plants reach problematic levels (Hitchcock 

 et al . , 1949) and maintain a low level of plants through a regular 

 patrol system to prevent reestablishment (Seale and Allison, 1946). 



