The Growth Substances separated from Plant Extracts by Chromatography. I

Methods for the chromatographic separation on paper of indolecompounds and for the direct biological assay of the chrornatograinsusing the Avena coleoptile straight-growth method are described.Reagents for the detection of the indole-3-carboxylic acids,indole-3-acetonitrile, and gramirte as coloured spots on chromatogramsare compared and the areas of such spots are shown to be proportionalto the logarithms of the quantities of substance present. The procedure of chromatography described is shown not to involvea loss of indole-3-acetic acid activity if chromatography isdone in darkness and chrornatograms are not stored in lightand air. Methods are described for the extraction of growth aubstancesfrom plant materials, the purification and chromatography, onpaper, of the extracts and the bioassay of the chromatogramsusing Avena coleoptile sections. The ether extracts, containing acidic substances, of etiolatedbroad bean and pea shoots and roots, etiolated sunflower shoots,maize roots, and potato etiolated shoots and tuber have beenchromatographed and the chromatograms bioassayed. On all chromatogramsthree areas active in Avena coleoptile section growth are found.One area of growth promotion is shown due to indole-3-aceticacid [IAA]. Another area of growth promotion and, one of growthinhibition are due to unknown substances, which are named accelerator () and inhibitor ß (ß) respectively. On chromatograms of potato tuber a fourth growth-promoting area,in addition to those described above, is detected and is shownto be probably due to indole-3-acetonitrile [IAN]. IAN or indole-3-pyruvicacid may occpr together with IAA on chrormatograms of extractsof immature maize kernels and cauliflower head respectively. On cabbage extract chromatograms the growth-promoting activitycorresponding in position with IAA is shown to be due to IAAand to IAA alone. In etiolated broad bean shoots IAA is the predominating growthsubstance in the stem and ß predominates in the firstlateral bud. The latter is suggested as an explanation of apicaldominance, and the predominance of ß in potato tuberskin is suggested as an explanation of dormancy in tubers. In the broad bean root the acidic growth-substance patterns,for the whole root and for the sections 0–2 cm. and 2–4cm. from the tip, are the same. The acidic growth substances extractable from broad bean shootsare the same whether the plant material is boiled or frozenbefore extraction.     

The Growth Substances separated from Plant Extracts by Chromatography: II. THE COLEOPTILE AND ROOT ELONGATION PROPERTIES OF THE GROWTH SUBSTANCES IN PLANT EXTRACTS

1. 1. A method for the running of ‘strip’ chromatogramsof plant extracts, as large-scale sources of the naturally occurringgrowth substances accelerator () and inhibitor ß(ß), and the elution of these substances togetherwith indole-3-acetic acid (IAA), is described. A method is givenfor the testing of the pea root section extension propertiesof these growth substances.
2. 2. Coleoptile and root sectionextension tests over a completeconcentration range are donefor , ß, and eluted IAA,and mixtures of and ßwith IAA or indole-3-acetonitrile(IAN) are tested for coleoptilesection extension.
3. 3. promotes at low concentrations andinhibits at high concentrationsboth coleoptile and root sectionextension and the coleoptilesection extension induced by IAAor IAN. ß inhibitscoleoptile and root section extensionover the whole concentrationrange; it also inhibits IAA andIAN induced coleoptile sectionextension.
4. 4. The extensionof coleoptile sections in mixtures of or ßwith IAAis measured at a number of time intervals. , aloneand withIAA, has its greatest promoting effect in the earlystages andits greatest inhibiting effect in the later stagesof sectiongrowth. ß, alone, promotes the early stagesand inhibitsthe later stages of section growth and, with IAA,has its greatestinhibitory effects in the later stages.

     

Some Growth Regulators of Tobacco in Relation to the Symptoms of the Physiological Disease 'Frenching'

Extracrts of the shoot tips of normal and ‘frenched’tobacco plants were chemically separated into acidic, neutral,and basic ether–soluble fractions. On chromatograms ofthese, some plant growth regulators were assayed using the Avenacoleoptile section extension test. The acidic auxins and an acids and a neutral growth inhibitorwere found. One auxin, with the samew R_F value as indole-3-aceticacid, was four times more concentrated on normal as in ‘frenched’plants. No differences could be established between the twotypes of plants in regard to other growth regulators detected. It is argued that the symptoms of the physiological disease‘frenching’ could be explained in terms of a auxindeficiency.     

The Extension Growth-Time Relationship for Avena Coleoptile Sections

1. The growth rates of coleoptile segments supplied with indole-3-aceticacid is not constant with time, but, when the IAA concentrationis high, decreases very rapidly.
2. With sufficiently high concentrationof IAA, the initial rapidgrowth may be eventually followedby shrinkage of the tissue.
3. The relation between initial rateof growth and auxin concentrationis not significantly differentfrom hyperbolic.
4. The significance of these facts in relationto kinetics of auxinaction is discussed.

     

The Growth Substances separated from Plant Extracts by Chromatography. I

For 0·per cent. sodium nitrite read 0·5 per cent. potassium ferricyanide