Natural auxins 



lAE. In the latter case, a 'bump' in the curve around 550 m^ probably 

 indicated the presence of lAA, liberated by hydrolysis under the influence of 

 perchloric acid. 



0-30 



WO 600 600 



VOO 500 600 

 Wavelength 



700 900 500 



600 



Figure 27. Absorption spectra, in visible light, of the coloured products formed on unwashed Whatman 

 No. 1 p'aper after spraying the spots of synthetic lAA, lAE, and IAN with the ferric-perchloride 

 reagent described in the text. These spectra change with time. 



The absorption maxima can be used to determine quantitatively, and 

 directly on the paper, amounts of lAA, IAN, and lAE as low as 0-5 y 

 {Figure 28) . This procedure avoids the losses which occur when one tries to 



0-300 



0-250 



'- lAA 



I _(j5(nin ,,5Wm^) 



^ UiiUU 



X 0-150 

 § 



X 



0-050 

 



lAE 

 \l00m\'n,130m}x) 



Z 18 3 1 



Gammas of auxin 

 Figure 28. Quantitative relationships between absorbency and amounts of lAA, lAE, and IAN when 

 measured directly on the paper after spraying with the ferric-perchloride reagent. 



eluate a substance from the paper. It requires that the spot be kept small and 

 that no interfering substances be present. Crude as these techniques may 

 still be, they nevertheless can assist in the difficult task of identifying 

 chemically the biologically active growth substances. 



In conclusion, it is hoped that this study of the extraction, chromatography, 

 bio-assay, and chemical identification techniques may be a help to those 

 engaged in the auxin field. 



REFERENCES 



BiTANCOURT, A. A., Schwartz, K., and Dierberger, R. (1954). La Nature des 

 auxines des tumeurs vegetales. C. R. Soc. Biol, Paris, 148, 822. 



Boysen-Jensen, p. (1941). Quantitative Bestimmung der beschleunigenden 

 Streckungswuchsstoffe in der sauren Fraktion der Atherextrakte aus hoheren 

 Pflanzen. Planta, 31, 653. 



30 



