55 



A total of 32 waterhyaci nths were placed in individual one-liter 

 beakers which were filled with 5 percent Hoagland's solution to 

 within 2 cm of the top. Nutrient solution volumes were replenished 

 approximately every 48 hours. Temperature in the growth chamber was 

 maintained between 16 (night) and 32 (day) C. Light was supplied by 



eight flourescent and eight incandescent bulbs which provided 330 



2 



micro-Eiensteins/M /sec at plant height. Based on the results of 



Patterson and Duke (1979), the plants could be expected to photosynthe- 

 size at approximately 78 percent of the rate expected at full sunlight. 

 The photoperiod simulated a 14-hour day and a 10-hour night. Prior to 

 treatment with the radioactive labeled 2,4-D, one-half or 16 of the 

 plants were individually removed from their beakers, the roots were 

 shielded with plastic, and the foliage was sprayed to the point of 

 "runoff" with 100 mg/1 aqueous solution of the potassium salt of gib- 

 berellic acid (Eastman Company). The plants were replaced in the 

 growth chamber, and the GA was allowed to dry on the plants prior to 

 the application of 2,4-D. 



Fifty milligrams of C ring-labeled 2,4-D, specific activity 

 940 AiCi/mM, was dissolved in 5 ml of ethanol . One ml (10 mg of 2,4-D) 

 of this solution was then added to 9 ml deionized water to yield a 

 1,000 mg/1 solution with an activity of 4.25 uCi/ml. A total of 0.216 

 uCi was applied by placing 51 ul of the 1000 mg/1 labeled 2,4-D solu- 

 tion in three separate 17 ul droplets on the lamina of a single leaf of 

 each of the plants, according to methods described by Singh and Muller 

 (1979a and 1979b). Treated leaves were either the fourth or fifth leaf 

 from the outside of the rosette of leaves, depending upon which was 



