Improvement of Growth Regulator Formulation 



799 



and hence makes for a slow but continued uptake of the toxicant. The 

 treated foliage remains green for several days after control plants 

 have been completely killed, yet regrowth is almost completely in- 

 hibited. 



Relative mobility is a property inherent in the regulator mole- 

 cules. Figure 5 shows one series, Figure 6 a similar series in barley. 

 If we could find a molecule that translocates as freely as MH and is 

 as toxic as 2,4-D, many of our problems of perennial weed control 

 would be solved. 



Finally, turning to soil application, there are inherent differences 

 in molecules with respect to uptake and distribution. Here we have 

 very little basic information. The following observations have been 

 made. When Ci^-labeled 2,4-D, lAA, amitrol, MH, urea, dalapon, 

 monuron, or simazin, or P^^ as phosphate are applied to roots of bar- 

 ley seedlings, 2,4-D, montiron, simazin, and lAA are absorbed suffi- 

 ciently to autograph strongly in 30 min. Monuron and simazin move 

 into the tops in 2 hrs. and continue to accumulate to the 8th day. 



4 Hrs. 8 Hrs. 



Fig. 8. Same as Figure 7, treatment times 4, 8, and 16 hrs. 



