Natural auxins 



Figure 1. If the concentration of lAA applied to the chromatogram is 

 plotted against per cent of light transmissions, a straight-line relationship 

 exists over the range 0-1 and 10 micrograms of lAA. 



The calculated error inherent in the quantitative paper chromatography 

 of lAA is within 3 per cent. This value is considerably below the values given 

 by Block, LeStrange, and Zweig (1952) for the determination of amino acids 

 by the maximum density method. 



0-05 



D1 



0-2 05 f-0 



S-'mdo/eacef/c acid 



50 



/^5 



Figure 1. A calibration curve for 3-indoleacetic acid based on densitometer readings of spots developed 

 with p-dimethylaminobenzaldehyde on paper chromatographs. 



EXTRACTION OF INDOLE COMPOUNDS FROM PLANT TISSUES 



It became apparent early in our study that a suitable extraction method for 

 lAA and other indole compounds from plant tissues was necessary before 

 quantitative paper chromatography could be utilized effectively (Vlitos and 

 Meudt, 1954a). An extraction method was needed which would (1) preclude 

 the conversion of tryptophan and other lAA precursors to lAA during 

 extraction, and (2) extract free lAA with a single extraction over a short 



period of time. 



While our work (Vlitos and Meudt, 1954a) was still in progress, a paper 

 appeared by Terpstra (1953) which adequately reviewed the problems 

 involved in the extraction or diffusion of auxins from plant tissues. Terpstra 

 has described a method for extracting auxin from Avena coleoptiles, and 

 from some green plant tissues, based on the water extraction of frozen 

 material and subsequent dissociation of the extracted auxin-complex with 

 ethyl ether. Kefford (1953) at about the same time described a method for 

 the extraction of free indole compounds from plant tissues using absolute 

 alcohol as the solvent. He found that all of the free auxin was obtained with 

 one extraction at — 12°C. We proceeded to evaluate the methods of Terpstra 

 and Kefford. Absolute ethanol was found to be a more efficient solvent than 

 water for the extraction of lAA and tryptophan from tomato or spinach 

 tissue {Tables 1, 2, and 3). 



The extraction of lAA from frozen plant tissue with absolute ethanol at 

 — 10°C was found to fulfil the requirements for an extraction method set 



58 



