Interaction of indoleacetic Acid with its inositol and glucoside conjugates in Avena coleoptile curvature

Avena coleoptile curvature is promoted by indoleacetic acid (IAA) IAA-glucoside, and IAA-inositol when these substances are applied in agar to the decapitated apical end of deseeded plantlets. Absorption of [³H]IAA-inositol over a wide range of concentrations during the 20 hour period of incubation is only 20 to 50% of the applied amount, compared with 85 to 92% of uptake of the applied [³H]IAA at equimolar concentrations. The absorption of IAA-glucoside could not be readily measured. The stimulation by both IAA-conjugates is very similar to that of free IAA at low concentrations (0.2 and 0.4 micromolar), but much less at higher concentrations. The interaction of free IAA with IAA-glucoside is additive or synergistic (depending on concentration). The interaction of free IAA with IAA-inositol is an inhibition (i.e. less than additive). The simultaneous application of equimolar concentrations of free IAA does not change the chromatographic pattern of the metabolic products of [³H] IAA-inositol. One of the more polar metabolites of [³H]IAA-inositol has chromatographic characteristics similar to the major polar metabolite of free [³H]IAA on an isocratically eluted reversed phase C₁₈ high performance liquid chromatography system that separates a number of IAA sugar and amino acid conjugates from each other, and from free IAA.     

Floral induction of vegetative plants supplied a purified fraction of deoxyribonucleic Acid from stems of flowering plants

It has been found that floral induced stems of flowering tobacco (Nicotiana tabacum cv. Wis. 38) plants contain large amounts of rapidly renaturing DNA, whereas noninduced stems of vegetative plants contain only small amounts. In addition, it has been shown that the striking qualitative difference in DNA between stems of flowering and vegetative plants mimics the over-all quantitative difference in DNA content (on a fresh weight basis). Therefore, the extra DNA in stems of flowering plants seems, at least in part, to represent preferential synthesis of rapidly renaturing DNA.     

Plant regeneration from leaf discs of peanut and pigeonpea: Influence of benzyladenine,indoleacetic acid and indoleacetic acid-amino acid conjugates

The influence of indoleacetic acid (IAA) and some IAA-amino acid conjugates in combination with benzyladenine (BA) on in vitro shoot regeneration from leaf discs of peanut and pigeonpea was investigated. The frequency of shoot regeneration and average number of shoot buds produced was dependent on the type of auxin present in the medium. Highest frequency of plant regeneration in peanut was induced by BA in combination with IAA or IAA-l-alanine, while in pigeonpea BA in combination with IAA or IAA-l-aspartic acid produced best results. Four hundred plants of peanut and 25 plants of pigeonpea were transplanted to soil.Abbreviations BA benzyladenine - IAA indoleacetic acid - IAA l-alanine-indole acetyl-l-alanine - IAA aspartic acid-indole acetyl-l-aspartic acid - IAA glycine-indole acetyl-l-glycine - IAA phenylalanine-indole-acetyl-l-phenyl-alanine     

Fractionation of nucleic acids with special regard to rapidly labeled RNA.

Fractionation of nucleic acids with potassium acetate is useful for studying the synthesis of ribosomal RNA and messenger RNA. By quantitative removal of 4 and 5 s RNA and of DNA, the detection of messenger RNA is facilitated.     

Xyloglucan oligosaccharide alpha-L-fucosidase activity from growing pea stems and germinating nasturtium seeds.

[14C]Fucose-labelled xyloglucan (XG) was synthesized from tamarind seed XG by incubating it with GDP-[14C]fucose plus solubilized pea fucosyltransferase, and [14C]fucose-labelled XG nonasaccharide was prepared from the parent hemicellulose by partial hydrolysis with fungal cellulase. alpha-L-Fucosidase activity was readily detected in crude enzyme extracts of growing regions of etiolated pea stems (Pisum sativum) and in cotyledons of germinating nasturtium seedlings (Tropaeolum majus) using the fucosylated XG-nonasaccharide as substrate. Both enzymes showed little activity against intact fucosylated XG and they were totally inactive against p-nitrophenyl-alpha-L-fucoside. Auxin treatment of pea stems, which greatly increased the activity of endo-1,4-beta-glucanases that hydrolyse XG in apical growing regions, failed to result in a similar increase in XG-nonasaccharide alpha-fucosidase activity. However, germination of nasturtium seed, which resulted in a large increase in endo-1,4-beta-glucanase (XG-ase) activity in the cotyledons, was accompanied by comparable increases in XG-alpha-fucosidase activity.     

Acid hydrolases in the suckling rat small intestine I. Fractionation of mucosal homogenates

Synopsis Small intestine mucosal homogenates of suckling rats have been fractionated by centrifugation and analyzed for acid hydrolases and for biochemical markers of subcellular organelles. The results indicate that the acid hydrolases are associated with particles having sedimentation properties similar to those of mitochrondria. The acid hydrolases exhibited latent activity. Subfractionation on a continuous density gradient of sucrose in deuterium oxide demonstrated that these enzymes are associated with particles distinct from other subcellular organelles. Electron micrographs of the acid hydrolase-rich region of the gradient show the presence of numerous small electron dense bodies bounded by a unit membrane.     

Responses of Avena coleoptiles to suboptimal fusicoccin: kinetics and comparisons with indoleacetic Acid

Proton excretion induced by optimal concentrations of indoleacetic acid (IAA) and fusicoccin (FC) differs not only in maximum rate of acidification but also in the lag before onset of H⁺ excretion and in sensitivity to cycloheximide. Because these differences might simply be a consequence of the difference in rate of proton excretion, FC and IAA have now been compared using oat coleoptiles (cv. Victory) under conditions where the rates of acidification are more similar, i.e. suboptimal FC versus optimal IAA. As the concentration of FC is reduced, the rate of H⁺ excretion decreases, the final equilibrium pH increases, and the lag before detectable acidification increases up to 7-fold. This enhanced lag period is not primarily a consequence of wall buffering, inasmuch as it persists when a low concentration of FC is added to sections which were already excreting H⁺ in response to IAA. An extended lag also occurs, upon reduction of FC levels, in the hyperpolarization of the membrane potential, before enhancement of O₂ uptake and before the increased rate of Rb⁺ uptake. The presence or absence of a lag is not a distinguishing feature between FC and IAA actions on H⁺ excretion and cannot be used to discriminate between their sites of action. In contrast, the insensitivity of FC-induced H⁺ excretion to cycloheximide, as compared with the nearly complete inhibition of this auxin effect by cycloheximide, persists even at dilute concentrations of FC. This seems to be a basic difference in H⁺ excretion by IAA and FC.     

Isolation and characterization of mutants of Arabidopsis thaliana with increased resistance to growth inhibition by indoleacetic acid-amino acid conjugates.

Two mutants of Arabidopsis thaliana that are resistant to growth inhibition by indole-3-acetic acid (IAA)-phenylalanine have been isolated. Both mutants were 2- to 3-fold more resistant than wild type to inhibition by IAA-phenylalanine, IAA-alanine, and IAA-glycine in root growth assays. The mutant icr1 (but not icr2) also shows some resistance to IAA-aspartate. Studies using 3H-labeled IAA-phenylalanine showed that the uptake of conjugate from the medium by icr1 was the same as wild type and was reduced by about 25% in icr2. No differences in hydrolysis of the exogenous conjugate were detected between the mutants and their wild-type parents. There was no significant metabolism of the IAA released from the [3H]IAA-phenylalanine, whereas exogenous [3H]IAA was rapidly metabolized to two unidentified products considerably more polar than IAA. Analysis of a cross between icr1 and icr2 indicated that these mutations were at distinct loci and that their effects were additive, and preliminary mapping data indicated that icr1 and icr2 were located at the top and bottom of chromosome V, respectively.     

The Biosynthesis of delta-Aminolevulinic Acid in Higher Plants: II. Formation of C-delta-Aminolevulinic Acid from Labeled Precursors in Greening Plant Tissues

δ-Aminolevulinic acid was accumulated by greening cucumber (Cucumis sativus L. var. Alpha green) cotyledons, barley (Hordeum sativum var. Numar) leaves, and bean (Phaseolus vulgaris L. var. Red Kidney) leaves in the presence of various ¹⁴C-labeled precursors and levulinic acid, a competitive inhibitor of δ-aminolevulinic acid dehydrase. The radioactivity in the accumulated δ-aminolevulinic acid was measured.