Investigation of natural auxins and growth inhibitors 



can be used in the detection of auxins on paper chromatograms. The first 

 example is taken from our work on fruits and concerns the auxins in the 

 seeds of Tokay grapes. The ether extract (2 hours at 0°C) of 3 g (fresh 

 weight) of the seeds of nearly ripe grapes was purified through hexane and 



Figure 21. Histograms showing the 

 biological activity of 1 (7/( sections of 

 chromatograms when incubated for 

 about 20 hours at 25"C in the dark 

 with 0-5 c.c. buffer -\- sucrose -{- Tween 

 80 {0- 1 per cent). The first histogram 

 shows the activity of an ether extract of 

 1-5 g (fresh weight) of seeds from nearly 

 ripe Tokay grapes {after purification 

 through hexane and acetonitrile) when 

 assayed with coleoptiles. The middle 

 histogram shows the activity of the same 

 extract when assayed with first inter- 

 nodes. The bottom histogram shows 

 the activity obtained with 18-0 g {fresh 

 weight) of the same material when 

 assayed with coleoptiles. The chromato- 

 grams were run in hexane -\- water. 



acetonitrile, and divided into two equal portions which were chromato- 

 graphed in hexane (90) -f- water (10) iyj^)- One chromatogram (correspond- 

 ing to 1 -5 g of grape seeds) was assayed with coleoptile sections, the other with 

 first internodes. The results with coleoptiles (^Figure 21, top diagram) were 

 inconclusive, except that a marked inhibition was obtained at the initial spot. 

 The first internodes, on the other hand, gave a clear-cut result (middle 

 diagram) with the same amount of grape extract, with a growth peak in the 

 IAN and another in the lAE position. No inhibitor was detected, for first 

 internodes are less sensitive to inhibitors than coleoptiles, their endogenous 

 growth being less. The growth peaks detected with internodes can, however, 

 also be detected with coleoptiles, but it is necessary to extract ten times more 

 material (bottom diagram). Thus, this first example shows that the use of 

 internodes instead of coleoptiles allows one to obtain a good picture of the 

 auxins present in an extract with at least ten times less plant material. 



A second example of the use of the internode test can be found in the 



25 



