. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). 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 dete
. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). 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 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
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