Auxins and the Process of Aging in Root Cells 



171 



OLD CELLS 



--0-- 

 YOUNG CELLS 



CONCENTRATION OF lAA, /Ig/mL 



Fig. 4. lAA destruction for the two types of fragments pretreated by lAA at 

 different concentrations for 20, 60, and 100 seconds. 



processes operate simultaneously. In other words, the tissues greatly 

 increase their ability to destroy native auxins in proportion to the 

 age of the roots at the same time as the accumulation of auxins is 

 increasing. Even if the destruction is greater, the final auxin content 

 rises because auxins are produced faster than they are destroyed. 

 These observations suggest a process of enzyme adaptation, or in- 

 duction, and work of a similar nature (6) performed on a different 

 material clarifies this phenomenon. If, before making the enzyme 

 extracts, the tissues are treated with lAA of increasing concentra- 

 tions and increasing time of incubation, the destructive power of 

 the extracts (which remains stronger for the tissues of the root cap 

 in relation to those of the meristem) increases slightly more for the 

 young than for the old cells (24, Figure 4). 



Several substances have been used which induced stimulation or 

 inhibition of the in vitro lAA destruction by Lens root tissues: 2,4- 

 dichlorophenol, 2,4-dinitrophenol, 2,4-dinitro-o-cresol and Mn^2 (jg)^ 

 maleic hydrazide (16), gibberellic acid (17), glutathione (20), and in- 



