Distribution of natural hormones 



appreciable concentration in the shoot of the young seedHng. It might there- 

 fore be tentatively suggested that auxin has little physiological significance 

 during the actual germination process but may be important in the 

 subsequent growth of the seedling shoot. 



In maize, the auxin content of the seed is considerably higher, and there 

 is a rapid increase in extractable auxin during the first 12 hours of germina- 

 tion. After about 48 hours when the radicles emerge, the auxin content is 

 decreasing. Our results, however, show that these changes are in the endo- 

 sperm only and that there is practically no lAA in the embryo and scutellum 

 at any stage of germination. The maize experiments provide no evidence of 

 a growth inhibitor, although such a substance may be present in the non- 

 acid fraction. Voss (1939) and Pohl and Tegethoff (1949) reported the 

 presence of an 'auxin inactivator' in the scutellum of maize, and since in this 

 investigation little auxin was found in the scutellum and embryo, it is 

 possible that indolylacetic acid moving out of the endosperm into the 

 scutellum is immediately inactivated by the scutellum 'Hemmstoff.' Skoog 

 (1937) and Voss (1939) obtained evidence that auxin precursor or inactivated 

 auxin was translocated to the coleoptile tip and was there re-converted to the 

 auxin which controls extension growth in the coleoptile. 



On the basis of all results reported in this paper, it would seem justified to 

 suggest, as a general hypothesis, that auxin extracted from seeds by the 

 procedure we have adopted is not of physiological importance during 

 germination. The growth of the seedling shoot, however, is clearly associated 

 with auxin production. 



REFERENCES 



Bennet-Clark, T. a., and Kefford, N. P. (1953). Chromatography of the growth 



substances in plant extracts. Nature, 171, 645. 

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



Streckungswuchsstoffe in der sauren Fraktion der Atherextrakte aus hoheren 



Pflanzen. Planta, 31, 653. 

 Fawcett, C. H., Taylor, H. F., Wain, R. L., and Wightman, F. (1956). The 



degradation of certain phenoxy acids, amides, and nitriles within plant tissues. 



This volume, p. 187. 

 PoHL, R., and Tegethoff, B. (1949). Der Hemmstoff des Maisscutellums — 



ein Wuchsstoffinaktivator. Naiurwissenschaften, 36, 319. 

 Seeley, R. C, Fawcett, C. H., Wain, R. L., and Wightman, F. (1956). Chromato- 

 graphic investigations on the metabolism of certain indole derivatives in plant 



tissues. This volume, p. 234. 

 Skoog, F. (1937). A deseeded Arena test method for small amounts of auxin and 



auxin precursors. J. gen. Phvsiol. 20, 311. 

 Smith, M. S., Wain, R. L., and Wightman, F. (1952). Studies on plant growth 



regulating substances. V. Steric factors in relation to mode of action of certain 



aryloxyalkylcarboxylic acids. Ann. appl. Biol. 39, 295. 

 Voss, H. (1939). Nachweis des inaktiven WuchsstofTes, eines Wuchsstoffantagoniste 



und deren Wachsumsregulatorische. Planta, 30, 261. 



39 



