Effects of cold on CO2 exchange in winter rape leaves

A viable wheat hybrid intermediate of the same height as the parents was obtained by crossing the female parent of tall variety NP4 with the male parent of the dwarf variety HD2160. Seeds of the hybrid and its parents were germinated and their growth pattern as well as the activities of peroxidase, indolyl-3-acetic acid oxidase and amylase in extracts made from them were studied at the early seedling stages i.e. up to 96 h.
A positive correlation existed between the length of the axis at the early seedling stage and at mature plant height as far as the parental varieties are concerned but no such correlation was observed with the hybrid. Growth of the hybrid seedlings was less than of its parents. Light appeared to stimulate the longitudinal growth of the axis to different extents in the parents and hybrid. Higher activities of peroxidase, indolyl-3-acetic acid oxidase and amylase were observed in the hybrid as compared to both of its parents. Lethal wheat hybrid also exhibits increased activities of amylase, indolyl-3-acetic acid oxidase and peroxidase. Therefore, it appears that seedling growth and enzyme activities at the seedling stage are not always correlated with hybrid vigour.     

Promotion of peroxidase activity in the cell wall of Nicotiana

Peroxidase catalyzes the oxidation of indole-3-acetic acid. The primary products of this reaction stimulate growth in plants. Therefore, our concept is that an increase in peroxidase activity will increase the effect of indole-3-acetic acid as a growth hormone. Our objective was to study the effect of 2,3,5-triiodobenzoic acid, a growth regulator, on isoperoxidases in the cell wall and cytoplasm of Nicotiana. Isoperoxidases from the cell wall and cytoplasmic fractions were separated by acrylamide gel electrophoresis. We found that 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase peroxidase activity in the cell wall. Since both 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase the activity of the same isoperoxidase, we conclude that 2,3,5-triiodobenzoic acid synergizes rather than antagonizes auxin action, and we suggest that this increase in indole-3-acetic acid oxidase activity sensitizes plant tissues to auxin.     

Effects of Seselin and Coumarin on Growth, Indoleacetic Acid Oxidase, and Peroxidase, with Special Reference to Cucumber (Cucumis sativa L.) Radicles

Seselin, a natural coumarin derivative isolated from citrus roots, inhibited radicle growth in seedlings of cucumber (Cucumis sativa), lettuce (Lactuca sativum), radish (Raphanus sativus), and wheat (Triticum aestivum) grown in the dark. Coumarin similarly inhibited radicle growth of cucumber seedlings. Growth retardation of the cucumber radicles was accompanied by an increased activity of peroxidase and indole-3-acetic acid oxidase. Both compounds antagonized indole-3-acetic acid-induced growth of wheat coleoptiles, whereas coumarin was much less effective than seselin in antagonizing gibberellic acid-induced release of reducing sugars from barley endosperm. It is suggested that seselin plays an important role in the regulation of root growth, and that it is the indole-3-acetic acid oxidase cofactor previously detected in citrus roots.     

The Effect of Pseudomonas putida Colonization on Root Surface Peroxidase

Increased activities of peroxidase and indole 3-acetic acid (IAA) oxidase were detected on root surfaces of bean (Phaseolus vulgaris) seedlings colonized with a soil saprophytic bacterium, Pseudomonas putida. IAA oxidase activity increased over 250-fold and peroxidase 8-fold. Enhancement was greater for 6-day-old than for 4- or 8-day-old inoculated plants No IAA oxidase or peroxidase activities were associated with the bacterial cells. Native polyacrylamide gel electrophoresis demonstrated that washes of P. putida-inoculated roots contained two zones of peroxidase activity. Only the more anodic bands were detected in washes from noninoculated roots. Ion exchange and molecular sizing gel chromatography of washes from P. putida-colonized roots separated two fractions of peroxidase activity. One fraction corresponded to the anodic bands detected in washes of P. putida inoculated and in noninoculated roots. A second fraction corresponded to the less anodic zone of peroxidase, which was characteristic of P. putida-inoculated plants. This peroxidase had a higher IAA oxidase to peroxidase ratio than the more anodic, common enzyme. The changes in root surface peroxidases caused by colonization by a saprophytic bacterium are discussed with reference to plant-pathogen interactions.     

Ferulic acid mediated changes in oxidative enzymes of maize seedlings: implications in growth

Maize (Zea mays L. cv. Ganga-5) seedlings were grown in the presence of ferulic acid (0.5 – 3.0 mM) for 8 d. Treatment with ferulic acid considerably decreased shoot and root length, increased the activity of peroxidase, catalase and indole-3-acetic acid (IAA) oxidase and decreased the activity of polyphenol oxidase. The increased activity of peroxidase correlated with pronounced increase in content of lignin and phenolic compounds     

Heat-Melt of β-1, 3-d-Glucan Gel

Six new products of oxidation of indolyl-3-acetic add catalyzed by horseradish peroxidase were isolated, along with four known ones, 3-hydroxymethyloxindole (1), 3-methyleneoxindole (2), indolyl-3-aldehyde (4), and 3,3-diindolylmethane (10). Based on spectroscopic and chemical evidence, the new products were identified as 3-acetoxyindole (3), 3-(indol-3-ylmethyl)oxindole (6), 3-[(2-mdol-3-ylmethyl)indol-3-ylmethyl]oxindole (9), the 3-hydroxymethyl compounds of 6 and 9 (5 and 7), and 2-(indol-3-ylmethyl)indolyl-3-acetic acid (8), respectively.     

Poly-N-vinylcaprolactam gel: A novel matrix for entrapment of microorganisms

Summary A new gel-type support poly-N-vinylcaprolactam for microbial cell immobilization is presented. The method allows one to obtain beads of biocatalyst in a single step. The properties of beads obtained using different types of gel stabilizers were compared; the best stabilizer was found to be tannin. The method developed was used for entrapment of viable bacterial cells and fungal spores. The biocatalysts obtained were used for transformations of both hydrophilic (sorbitol, indolyl-3-acetic acid) and lipophilic (cortexolone, hydrocortisone) substrates.Abbreviations PVC poly-N-vinylcaprolactam - ImC immobilized cells - IAA indolyl-3-acetic acid - TLC thin layer chromatography     

Hydroxylation of indolyl-3-acetic acid by immobilized mycelium of Aspergillus niger

Summary The immobilization in polyacrylamide gel (PAAG) of the Aspergillus niger mycelium, which has the activity of hydroxylating indolyl-3-acetic acid (IAA) at 4-, 5-, and 6-positions of the indole nucleus, was studied. To preserve the hydroxylating activity, the immobilization should be performed at 5°C–10°C for 5–10 min. The hydroxylating activity of the A. niger mycelium entrapped in PAAG attained 70%–80% of that of free cells. The IAA transformation in the presence of sodium desoxycholate, polyethylene-glycol-400 (PEG-400), Span-60 or preincubation of granules entrapping mycelia in the presence of Tween-80 or PEG-400 not only double the hydroxylation rate but stabilize the activity as well. Gels entrapping mycelia may be used five or six times without altering activity. Incubation of gels with mycelium in the nutrient medium also increases and stabilizes the hydroxylating activity. In aerated columns, it is possible to obtain continuous hydroxylation of IAA, at a concentration of 0.5 g/l, by the immobilized mycelium of A. niger. The yield of hydroxy derivatives reached 70%, the activity remaining unaltered during 15 days' operation of the column.     

Differential identification of natural forms of indolyl-3-acetic acid

An original micromethod ELISA for differential quantitative determination of free (indolyl-3-acetic acid) and bound (indolyl-3-acetyl-L-aspartic acid) forms of auxins is suggested. Our immunoassay approach is basic and may be applied to problems in biology, medicine, agriculture, and environmental protection for the identification of low-molecular compounds related in chemical structure and characterized by different biological activity.     

Oxidation of Indole-3-Acetic Acid to Oxindole-3-Acetic Acid by an Enzyme Preparation from Zea mays

Indole-3-acetic acid is oxidized to oxindole-3-acetic acid by Zea mays tissue extracts. Shoot, root, and endosperm tissues have enzyme activities of 1 to 10 picomoles per hour per milligram protein. The enzyme is heat labile, is soluble, and requires oxygen for activity. Cofactors of mixed function oxygenase, peroxidase, and intermolecular dioxygenase are not stimulatory to enzymic activity. A heat-stable, detergent-extractable component from corn enhances enzyme activity 6- to 10-fold. This is the first demonstration of the in vitro enzymic oxidation of indole-3-acetic acid to oxindole-3-acetic acid in higher plants.     

Effect of phytohormones on fiber initiation of cotton ovule

In order to study the effect of phytohormones on cotton fiber initiation, contents of four endogenous phytohormones and activities of four related enzymes in ovules (in vivo) of a fuzzless–lintless mutant (fl) and its wild-type (FL) line were measured from 4 days before anthesis (day −4) to 4 days after anthesis (day 4). The results showed that contents of indole-3-acetic acid, gibberellic acid (GA), and zeatin riboside in fl ovules were lower than those in FL ovules. Therefore, indole-3-acetic acid, GA, and zeatin riboside were thought to be the promoters of fiber initiation. Although abscisic acid (ABA) content in fl ovule was slightly higher than that in FL ovule on day 0, which might imply that ABA inhibited fiber initiation. Fiber initiation could also be influenced by enzyme through regulating synthesis and degradation of related phytohormones since fl ovules were significantly higher in activities of indole-3-acetic acid oxidase, cytokinin oxidase and peroxidase, but lower in activity of tryptophan synthetase than those in FL ovules. To test the above hypothesis, exogenous plant growth regulators were also applied for the culture of ovules from fl and FL in vitro. When no regulators were added, no fiber was induced on fl ovule, but a few fibers were induced in FL ovule. Higher total fiber units (TFU) were observed when indole-3-acetic acid and gibberellic acid (GA₃) were applied either separately or in combination to media. TFU did not increased with zeatin riboside alone, but the highest TFU was achieved when zeatin riboside was applied together with indole-3 acetic acid and GA₃, which implied that fiber initiation could be promoted by them as additive.     

Plant hormone interaction and phenolic metabolism in the regulation of russet spotting in iceberg lettuce

Russet spotting (RS) is a physiological disorder induced in iceberg lettuce (Lactuca sativa L.) by exposure to parts per million levels of ethylene at 5 ± 2°C. Ethylene induced phenylalanine ammonia-lyase and ionically bound peroxidase activities that correlated with development of RS symptoms. The ethylene-treated tissue had significantly higher lignin content than air control tissue with lignification localized in walls of RS-affected cells. Ethylene also caused the accumulation of the flavonoids (+)catechin and (−)epicatechin and the chlorogenic acid derivatives 3-caffeoyl-quinic acid, 3,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid. These soluble phenolic compounds were readily oxidized to brown substances by polyphenol oxidase isolated from RS tissue. Ethylene substantially increased ionically bound indole-3-acetic acid (IAA) oxidase activity, while IAA application greatly reduced ethylene-induced phenylalanine ammonia-lyase, peroxidase, and IAA oxidase activities, soluble phenolic content, and RS development.     

A rapid,sensitive and accurate determination of indolyl-3-acetic acid

A method is described for the routine determination of absolute amounts of free indolyl-3-acetic acid (IAA) in plant material. The time required for a determination is in the order of 2 hr. Several samples can be handled at the same time. Depending on the contents of IAA, the amount of fresh plant material varies from 0·05 to 5 g. Losses are corrected for by applying ¹⁴C-labeled IAA.     

Tea catechol oxidase: Isolation,purification and kinetic characterization

Cathechol oxidase extracted from tea leaves was purified over 200-fold, using isoelectric focusing. The purified catechol oxidase was free of peroxidase and flavanol gallate esterase activities. Further, this enzyme was shown to have optimum activity near pH 5·7 and a K_m of 2·3 × 10^?3 M (at 25°) for (?)-epigallocatechin gallate. The purified enzyme was found to be capable of epimerizing tea flavanols at their C-2 position whether oxidation of the flavanol occurs (aerobic conditions) or not (anaerobic conditions). When oxygen is present, gallic acid is formed as a result of oxidation of either (?)-epigallocatechin gallate or (?)-epicatechin gallate. Formation of gallic acid is a side reaction of the oxidation of the flavanol gallates and is named oxidative degallation; no esterase per se is involved in this reaction.     

Translocation of Radiolabeled Indole-3-Acetic Acid and Indole-3-Acetyl-myo-Inositol from Kernel to Shoot of Zea mays L.

Either 5-[³H]indole-3-acetic acid (IAA) or 5-[³H]indole-3-acetyl-myo-inositol was applied to the endosperm of kernels of dark-grown Zea mays seedlings. The distribution of total radioactivity, radiolabeled indole-3-acetic acid, and radiolabeled ester conjugated indole-3-acetic acid, in the shoots was then determined. Differences were found in the distribution and chemical form of the radiolabeled indole-3-acetic acid in the shoot depending upon whether 5-[³H]indole-3-acetic acid or 5-[³H]indole-3-acetyl-myo-inositol was applied to the endosperm. We demonstrated that indole-3-acetyl-myo-inositol applied to the endosperm provides both free and ester conjugated indole-3-acetic acid to the mesocotyl and coleoptile. Free indole-3-acetic acid applied to the endosperm supplies some of the indole-3-acetic acid in the mesocotyl but essentially no indole-3-acetic acid to the coleoptile or primary leaves. It is concluded that free IAA from the endosperm is not a source of IAA for the coleoptile. Neither radioactive indole-3-acetyl-myo-inositol nor IAA accumulates in the tip of the coleoptile or the mesocotyl node and thus these studies do not explain how the coleoptile tip controls the amount of IAA in the shoot.     

Role of auxin in induction of polarity in zygotes of Fucus vesiculosus L

We studied the effects of auxin (indolyl-3 acetic acid) on formation of the primary polarity axis in zygotes of the brown algae Fucus vesiculosus. Within the first 2.5 h after fertilization, the zygotes release this phytohormone in the environment. The treatment of developing zygotes with the inhibitor of indolyl-3-acetic acid transport from the cell triiodobenzoic acid at 5 mg/l arrests the auxin secretion and leads to its accumulation in the cells. This causes a significant delay in zygote polarization. The treatment of zygotes with the exogenous indolyl-3-acetic acid at 1 mg/l stimulates cell polarization and formation of a rhizoid process. When auxin was added to the medium with triiodobenzoic acid, the inhibitory effect of the latter was fully relieved. It has been proposed that the content of indolyl-3-acetic acid in the environment is a key factor in the induction of polarity of the F. vesiculosus zygotes.     

Metabolism of14C-abscisic acid during its IAA-promoted transport in etiolated segments of pea (Pisum sativum L.) epicotyls†

The metabolism of exogenously supplied abscisic acid (ABA) during translocation attracted under the influence of indolyl-3-acetic acid (IAA) was studied in etiolated segments of pea (Pisum sativum L.). After 8 and 24 h 90% and 60% of the ABA, respectively, were found in the segments in unchanged form. Phaseic acid, dihydrophaseic acid and the glucose ester of ABA were found as ABA metabolites. Results indicated that the growth processes initiated by the application of IAA were associated neither with an increased immobilization nor increased metabolization of this growth regulator. † Part II. Influence of Auxin-like Substances upon the Transport of¹⁴C-ABA in Long Pea Epicotyl Segments.     

Cucumber seedling indoleacetaldehyde oxidase

Extracts of light-grown Cucumis sativus L. seedlings catalyzed the oxidation of indole-3-acetaldehyde to indole-3-acetic acid. No added cofactors were required. Inhibitor studies indicated that the enzyme is a metalloflavoprotein. While indole-3-aldehyde, benzaldehyde, and phenylacetaldehyde partially inhibited the oxidation of indole-3-acetaldehyde, suggesting that they may serve as alternative substrates, it is proposed that indoleacetaldehyde is the major substrate in vivo. 2,4-Dichlorophenoxyacetic acid strongly inhibited the indoleacetaldehyde oxidase activity, and it is proposed that this enzyme may be subject in vivo to feedback inhibition by indole-3-acetic acid. The enzyme was activated by brief heating or by treatment with mercaptoethanol.     

Comparative aspects of root and root nodule secondary metabolism in alfalfa

l-phenylalanine ammonia lyase (PAL), indoleacetic acid oxidase (IAA oxidase), O-methyltransferase, peroxidase, total phenolics and total indoles were compared in roots and root nodules of alfalfa. PAL, O-methyl-transferase, total phenolics and total indoles were higher in nodules than in roots. Isolated bacteroids were assayed for O-methyltransferase, PAL, peroxidase and total phenolics, but their levels were either low or not detectable. Nodule leghemoglobin was separated by disc gel electrophoresis and found to have IAA oxidase activity. Phenolics, IAA oxidase and leghemoglobin appear to be interrelated in regulating indole levels in the nodule.