Auxins (1)1(1 the Process of Aging in Root Cells 



173 



12 



o 

 ^ 10 



O YOUNG CELLS 

 • OLD CELLS 



80 



40 60 



TIME IN MINUTES 

 Fig. 5. lAA destruction for two types of fragments with or without 2,4-dichloro- 

 phenol (DCP) at 1 x 10''^ M, in relation to time. 



dole (19). It is a general observation (Table 2) that the stimulation 

 is stronger when the activity is stronger. 



Study of the progress of lAA destruction (Figure 5) shows that 

 in the case of the tip tissues, the decomposition of lAA is almost 

 immediate, although, for the meristem, there is a certain time lag 

 (6). Treatment with 2,4-dichlorophenol (DCP) alters this process, 

 since it induces an immediate stimulation of lAA destruction in 

 the two root fragments. This seems to indicate that lAA-oxidase in- 

 duction cannot be expressed in terms of adaptive formation of en- 

 zyme since, in young cells, DCP (substance without action on non- 

 enzymatic lAA destruction) produces immediately a dramatic stim- 

 ulation of lAA-oxidase which was already present in the tissues but 

 probably bound. 



BIOCHEMICAL ANALYSES 



It was essential to establish, for the analyzed tissues, the nature 

 and importance of some biochemical gradients: first, to see if a cor- 

 relation existed between these gradients and the aging of cells (19, 

 28); secondly, to express more logically and to compare on the same 

 basis (23, 30) the native auxin content and lAA-destroying activity. 

 Data are shown in Table 3, and it can be seen that, regardless of 



