CHROMATOGRAPHIC INVESTIGATIONS ON 



THE METABOLISM OF CERTAIN INDOLE 



DERIVATIVES IN PLANT TISSUES! 



R. C. Seeley 

 Chemistry Department, Wye College, University of London 



and 



C. H. Fawcett, R. L. Wain, and F. Wightman 



Agricultural Research Council Unit on Plant Growth Substances and 

 Systemic Fungicides, Wye College, University of London 



INTRODUCTION 



Of the indole derivatives known to be active as plant growth substances, 

 indole-3-acetic acid has been shown to be widely distributed in plant tissues, 

 while indole-3-acetonitrile, indole-3-acetaldehyde, and ethylindole-3- 

 acetate have been identified in tissue extracts of several plant species. It is 

 generally believed that indole-3-acetic acid has primary auxin activity, i.e. is 

 active per se, but the mode of action of other indolyl derivatives is still a 

 matter of conjecture. In the present investigations some information on the 

 fate of indolyl compounds in various plant tissues was obtained by applying 

 methods similar to those used at Wye in studies on the breakdown of 

 fo-phenoxyalkanecarboxylic acids, amides, and nitriles in plants (Fawcett, 

 Taylor, Wain, and Wightman, 1956). Briefly, the over-all procedure 

 involved exposing solutions of indolyl derivatives to plant tissue with sub- 

 sequent extraction and paper chromatographic separation of the products in 

 the tissues and in the residual solution. After development, the chromato- 

 grams were examined by chromogenic and biological methods. 



MATERIALS AND METHODS 



The compounds examined were indole-3-acetic acid (lAA), indole-3-aceto- 

 nitrile (IAN), indole-3-acetamide (lAAm), and methyl indole-3-acetate 

 (lAMe). Solutions of pure samples of each of these substances were exposed 

 separately to pea stem, wheat and maize coleoptile, and tomato and celery 

 petiole tissues. In each treatment one hundred 1 cm segments of tissue were 

 floated on 50 ml of aqueous solutions containing 500 jiig (10 p.p.m.) of the 

 substance. The solutions were incubated for 18 hours at 25°C, a water plus 

 tissue control being included with each batch of treatments. 



The solutions and tissues were extracted separately. Solutions were 

 acidified to pH 6-5, extracted three times with peroxide-free ether, the 

 combined ether layers dried over sodium sulphate, and the ether removed. 

 The tissues were first washed several times with water and then immersed in 

 peroxide-free ether at 10°C for 24 hours. The ether was then decanted off", 



•f This paper was read at the Conference by R. C. Seeley. 



234 



