Effects of synthetic growth substances in level of endogenous auxins in plants 



lAA equivalents) showed erratic fluctuations and there were no consistent 

 effects of treatment. With lAA, on the other hand, the table shows that, with 

 one exception, levels in treated roots are higher than those in controls. A 

 statistical analysis shows this effect to lie just on the 5 per cent level of 

 significance, indicating the need for further confirmatory work. It seems 

 unlikely, however, that these relatively small increases in free lAA content 

 could account for the growth inhibitions produced by these maleic hydrazide 

 treatments. Furthermore, they might be expected to promote rather than 

 cause the inhibition of lateral root production, which was in fact observed. 

 In view of the other marked metabolic disturbances now known to be 

 produced by this compound in plants, it seems logical to suppose that these 

 altered auxin levels are additional expressions of these general disturbances 

 and have no direct part to play in growth inhibitions by maleic hydrazide. 



(d) The effect of TIB A treatment 



This compound has an R^ the same as that of inhibitor-^ and so only lAA 

 levels have been followed in these experiments. The results of treatment of 



Table 3 



pea roots are shown in Table 3 and chromatograms from a typical experiment 

 in Figure 1. Here it will be seen that TIBA treatment has produced a dramatic 



tzo 



110 



I 



\100 



V 



30 



80 



§ 



I 



^70 

 I 



1 



eo 



— • — Control (31-6 if) 

 — = — Tpeafec/(80-3 g ) 



0-1 



0-Z 



0-3 



_L 



J 



I ^% 

 F/duci'o/ 

 /I'mifs 



0-7 



0-8 



OS 



O-f 0-5 0-6 

 Re value —— 



Figure 1. Pea roots (9 days from germination). Treatment — 7 days in \0 p.p.m. 2:3:5-triiodo- 

 benzoic acid. Acid fraction. 



251 



