43 

 tissue, and weighing the plants to the nearest 0.0 g in order to determine 

 post-treatment biomass. Periodically, plants were placed in a drying 

 oven at 65 C for 72 hours to determine dry to fresh weight ratios. Dry 

 to fresh weight ratios obtained from subsamples were used to calcu- 

 late final dry weights of all treated plants. 



Results were analyzed by general linear regression procedures. The 

 resulting analysis of variance was used to conduct a trend analysis for 

 regression of the response of the mean percent change in biomass and 

 number of plants caused by the main effects of GA3 and 2,4-D and their 

 interaction (Chew, 1977). Means of the percent change in biomass and 

 number of plants due to discrete treatment levels were also compared 

 using the Waller-Duncan procedure. The Waller-Duncan procedure was 

 employed in lieu of other multiple comparison methods because it has the 

 advantage of using the observed overall F-value in the calculation of 

 the least significant difference (LSD). This characteristic provides a 

 mechanism for accounting for both the comparisonwise and experimentwise 

 Type I error rates, the lack of which has been a major criticism of the 

 standard Duncan Multiple Range Test (Chew, 1977). 



Results and Discussion 

 Tables 1-1 and 1-2 present the analysis of variance of mean percent 

 changes in dry weight and number of waterhyacinths, respectively, due to 

 treatment with combinations of GA3 and 2,4-D excluding the 2.24 kg/ha 

 2,4-D treatment. Analysis of Tables 1-1 and 1-2 indicates that the 

 variability between trials was highly significant (a=0.01) and accounted 

 for more of the variability than the differences between replications 

 within trials. The overall response of waterhyacinths to GA 3 and 2,4-D 



