Abstract of Dissertation Presented to the Graduate Council 

 of the University of Florida in Partial Fulfillment of the 

 Requirements for the Degree of Doctor of Philosophy 



EFFECT OF GIBBERELLIC ACID 

 AND 2,4-DICHLOROPHENOXYACETIC ACID ON 

 WATERHYACINTH, EICHHORNIA CRASSIPES (MART.) SOLMS 



By 



JOSEPH CLARENCE JOYCE 



December 1982 



Chairman: William T. Haller 



Major Department: School of Forest Resources and Conservation 



Effects of combinations of gibberellic acid (GA 3 ) and 

 2,4-dichlorophenoxyacetic acid (2,4-D) on waterhyacinths ( Eichhornia 

 crassipes (Mart.) Solms) were evaluated to determine if GA 3 increased 



waterhyacinth sensitivity to 2,4-D under field conditions, and if 



14 

 GA 3 increased translocation of C labeled 2,4-D in waterhyacinths grown 



in growth chambers. Effects of GA 3 on waterhyacinth sensitivity to 



2,4-D were evaluated in two phases. In the first phase, small bulbous 



leafed waterhyacinths were grown outdoors in 70-1 iter containers and 



treated during three growing seasons with combinations of GA 3 at 0.0, 



23.5, 47.0, 94.0 and 188 g/ha and 2,4-D at 0.00, 0.28, 0.56, 1.12, and 



2.24 kg/ha. The second phase was conducted during late summer in a 



dense population of mature, non-bulbous leafed waterhyacinths in the 



vii 



