Natural auxins 



The cress assay method was a modification of that used by Moewus 

 (1949a and b). Seeds, placed 1 cm apart, were germinated in Petri dishes 

 lined with wet filter paper. 24-28 hours later, 6 seedlings with roots of 

 5 mm length were placed into a 2 in. Petri dish containing 10 ml 1-5 per cent 

 agar into which the test solution had been previously incorporated. Approxi- 

 mately 1 7 hours later the root lengths were determined to the nearest mm by 

 measuring on graph paper after removal from the agar medium. The assay 

 was carried out at 27°C in phototropically-inactive light, and subsequent 

 root growth was at 25°C in the dark. 



i" 



77 



1^ 



13 



10 



Response to lAA 

 (Tng/L) 



0-2 



0-f 0-e 



0-8 



18 





n 



I 



w 



lAA 



1-0 



IAN 



V 



10 \ 



<5> 



w?fi 



18 3 



[ZZ] 



Response to lAA 

 (mg/l.) 



0-2 



0-f 



0-e 



0-8 



1-0 



Figure 1. Chromatography in ammoniacal isopropanol (a) and n-butanol (b) of the aqueous fraction of 

 an extract of cabbage leaves. U.v. fluorescence on the chromatograms is shown below, (a) ^one 1 yellow 

 pigment on blue background, 2 blue with faint purple, 3 bluish-purple, (b) ^one 1 light blue, 2 purple, 

 3 bluish-purple, 4 bluish-purple. 



RESULTS 



Aqueous fraction of cabbage 



Chromatography of the syrup (approximately 50 mg) obtained from 

 distillation of the aqueous fraction was carried out initially in /jopropanol/ 

 ammonia; a typical result is shown in Figure J (a). Peaks of growth promo- 

 tion were obtained at the lAA and IAN zones; chromogenic sprays gave 

 shades of yellow with ferric chloride/perchloric acid and with nitrous/nitric 

 acid between R^ 01 and 0-5. Near the IAN region nitrous/nitric acid 

 produced a pale mauve colour resembling that of IAN at low concentration. 



The demonstration of a growth promoter in the I AA zone but not giving 



42 



