HORMONES AND HORMONE PRECURSORS 

 IN LEAVES, ROOTS, AND SEEDSt 



Joyce A. Bentley,J S. Housley, and G. Brixton 



Department of Botany, Manchester University 



This work is concerned with the naturally occurrinsr hormones and their 

 precursors in several plant tissues. The substances studied have been located 

 in the main by paper chromatography of plant extracts and bio-assay of the 

 separated fractions for physiological activity. So far, workers have concerned 

 themselves almost entirely with the acid ether-soluble constituents of plant 

 extracts, and evidence has accumulated that there are several active sub- 

 stances in this fraction. 3-Indolylacetic acid (lAA), 3-indolylacetonitrile 

 (IAN), 3-indolylpyruvic acid (IPyA), accelerator-a, and an inhibitor have 

 all been demonstrated or postulated by various workers on the evidence of 

 zones of activity obtained at various R/s on paper chromatograms run under 

 specified conditions. 



In this paper other fractions of plant extracts, in particular the aqueous, 

 non-ether-soluble fraction, have been examined and have led to evidence of 

 other active substances and hormone precursors. The presence of IAN in an 

 acid ether fraction, reported in particular by Bennet-Clark and Kefford 

 (1953) in their extracts oi Aegopodium rhizomes and potato tubers, was of 

 interest to us, since we have obtained evidence of a neutral, ether-soluble 

 substance with R^ and chromogenic reactions of the nitrile being released 

 from a water-soluble precursor. An acidic water-soluble precursor of a 

 neutral growth substance in cabbage has already been reported by Bonde 

 (1953). In view of these reports it was decided to examine the aqueous 

 fractions of our extracts. 



In addition, work on synthetic IPyA led us to reorganize our views on the 

 role of this substance as a plant hormone and the possibility of its being 

 identical with Bennet-Clark's accelerator-a. 



TECHNIQUES 



All commercially-supplied cheinicals were of the pvu^est grade obtainable. 

 Anaesthetic ether was rendered and maintained peroxide-free by standing 

 over sodium wire in darkness at 0°C. Glass-distilled water was used for 

 preparing all solutions. Oats (var. Victory) of the 1951 harvest were used in 

 the bio-assays. 



Extraction techniques 



(a) Cabbage — A single plant was collected in early October 1953, the 

 inner etiolated leaves frozen and ground, and extracted with 95 per cent 

 ethyl alcohol acidified to pH 3-2 with sulphuric acid for 40 hours at — 10°C. 

 The pH of the tissue-free extract was raised to 5 with barium hydroxide, the 

 extract filtered, and the alcohol removed at 35°C by distillation under 



f This paper was read at the conference by Joyce A. Bentley. 

 J Present address: Marine Laboratory, Torry, Aberdeen. 



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