SKOOG AND TSUI 



277 



above the optimum requirement and no better than the standard 

 amount. 



Variations in potassium concentrations as stated above appear to have 

 no effect on bud formation. Different NO3" levels have been tested only 

 in callus cultures not suppHed with adenine. No significant effect on the 

 capacity of the tissues to form buds was obtained in these experiments. 

 Other components may have some effect but have not been studied in 

 detail. 



Interactions of I A A, adenine, ribose, and phosphate.- — Since the meta- 

 boUcally active nucleotides contain ribose as well as phosphate combined 

 with adenine it was of interest to test effects of ribose on growth and 



(J) 



\- 

 z 



u 

 c/) 



O 

 tr 



Ld 

 Q. 



Q 

 LJ 



cc 

 O 

 u. 



to 



Q 



D 

 DD 



10 20 30 40 



TIME IN DAYS 



Figure 8. Effect of phosphate concentration on bud formation in tobacco 

 stem segments treated with adenine sulfate. Exp. #32. Started 7/17/48. 

 Initial pW 4.0. Curves: i. control without adenine, KH2PO4 12 mg./l.; 

 2. adenine sulfate 40 mg./l.; KH2PO4 12.5 mg./l.; 3. same as 2 except KH2PO4 

 37.5 mg./l.; 4. same as 2 except KH2PO4 1 12.5 mg./l. 



