Interconvertible Naturally Occurring Auxins 37 



Z are released to a limited extent from an unstable water-soluble 

 complex by manipulative treatments during extraction, and so would 

 be found in the acidic ether fraction without any alkaline treatment. 



The interconvertibility of X and Z may be related to a similar 

 phenomenon observed in extracts of tomato roots, in which three 

 compounds, X, Y, and Z, were shown to be mutually interconver- 

 tible (3). The same phenomenon is also reported in extracts of pea 

 roots (1). The behavior of the tomato X and Z on chromato- 

 grams corresponds to the behavior of the algal X and Z considered 

 here. There is also evidence on several of the algal chromatograms of 

 the existence of zone Y, though this is only transient. This may be be- 

 cause chromatography in the present work was usually in ammoniacal 

 isopropanol. It was shown in work on tomato roots that X and Y may 

 not be separated in this solvent mixture, whereas they are easily sepa- 

 rated in ammoniacal butanol. Zone X in tomato, when separated from 

 zone Y, usually ran behind lAA; this has been noted in the present 

 work also. 



If the tomato and pea auxins are the same substances as the algal 

 hormones, we are obviously dealing with auxins of wide distribution 

 in the plant kingdom and probably of importance in fundamental 

 cell metabolism. It is clearly important that their chemical constitu- 

 tions should be investigated further. The interconversions demon- 

 strated between X, Y, and Z suggest that the compounds are probably 

 closely related chemically. 



The two zones of major activity (X and Z) on the chromatograms 

 correspond to the positions of lAA and IAN on chromatography 

 in ammoniacal isopropanol, so that it is obviously necessary to deter- 

 mine whether these two latter compounds are present. Zone X us- 

 ually survives autoclaving with N HCl (e.g.. Figure 2B). lAA, which 

 is popularly supposed to be destroyed by acid, is only partially de- 

 composed under the conditions used here. However, lAA does not 

 give activity in zone Z on rechromatography, as zone X does. This 

 fact does not rule out the possibility that some lAA may be present 

 in addition to another compound. 



Zone Z contains one or more indole compounds, but probably 

 not indole-3-acetonitrile, since it does not give the same color reac- 

 tions as IAN. Z sometimes gives a pink or purple Ehrlich reaction, 

 a pink Salkowski reaction, and pink nitrite-nitric acid reaction. In- 

 dole-3-acetonitrile gives a purple Ehrlich, blue-purple Salkowski, and 

 fading blue nitrite-nitric acid reactions. 



Chlorella 5, which occurs in the acidic ether fraction and some- 

 times the acidic saponified fraction of Chlorella and which runs at 

 an Rf of 0.8 to 0.9 in ammoniacal isopropanol, gives markedly char- 



