SKOOG AND TSUI 



271 



and are transplanted, however, they grow into normal mature plants. 

 Effects of lAA or NAA treatments. — Even though there are important 

 quantitative differences in growth responses to lAA and NAA, the 

 general effects of these substances in the present experiments are closely 

 enough alike, so that they can be considered together. The addition of 

 either lAA or NAA to the medium markedly stimulates the growth of 



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Figure 4. Effect of concentration of adenine sulfate on bud formation in 

 tobacco stem segments. Exp. # 76 started 5/2/49. Curves in order from the top 

 represent treatments with 40, 20, 10 and mg./l. adenine respectively. 

 Initial pH 4.0, KH2PO4 concentration 37.5 mg./l. 



the tissues through both enlargement of existing cells and the formation 

 of callus over wider areas of the segments. 



Significant increase in callus growth and decrease in bud formation 

 may be obtained with as little as 0.02 mg./l. and maximum effects with 

 concentrations in the range from i to 10 mg./l. These substances also 

 induce the formation of roots as indicated in Figures 2 and 3, which effect 

 is comparable to that known to occur in cuttings. 



Effects of adenine plus lAA or NAA. — Combined treatments with 



