p. E. PILET 



University of Lausanne 

 Switzerland 



Auxins and the Process of Aging in Root Cells 



The relationship between the aging of plant tissues and auxin 

 metabolism has been discussed in a number of papers by several 

 investigators (5, 14, 18, 30). Among these, the work of Galston and 

 Dalberg (6) is of special interest, for they have shown that the ability 

 of pea seedling cells to destroy the native auxins increases as the cell 

 ages. The purpose of this paper is to analyze various biochemical 

 properties of root cells in relation to indole-3-acetic acid (lAA) 

 destruction. The advantage of working with root sections is that they 

 possess, simultaneously, both very young tissues (meristem) and older 

 ones (root tip). 



MATERIALS AND METHODS 



The experimental material used was Lens culinaris Med. The 

 seeds were selected and nearly 100 per cent germination occurred 

 after 38 hrs. Seeds were first soaked in de-ionized water for 12 hrs., 

 then washed, and finally placed on wet filter paper in petri dishes 

 in darkness at 22 ± 0.5° C. The first selection was made after 24 hrs., 

 and only seedlings measuring 3 ± 1 inm. were kept and replaced in 

 the above conditions. The seedlings were removed for treatment 

 when they had reached a length of 18 rb 2 mm., for this has been 

 found to be the period of optimal growth (11,29). A series of cyto- 

 logical analyses has shown that the tip, composed of older cells, is 

 located between the extreme point and 0.5 mm. from it while the 

 meristem, containing the young cells, is situated in the region from 

 0.5 to 3.0 mm. The work on the process of aging was done ex- 

 clusively on these two types of fragments. In order to prepare these 

 two root sections, a small guillotine (22) was developed (Figure 1); 

 it is a modified version of a design by Linser and Kiermayer (10). 



[167] 



