Effect of indoleacetic Acid and hydroxyproline on isoenzymes of peroxidase in wheat coleoptiles

Indoleacetic acid at 0.017 millimolar inhibited the formation of three peroxidase isoenzymes in both soluble and wall-bound enzyme fractions of wheat coleoptile (Triticum vulgare) tissue. Hydroxyproline at 1 millimolar prevented the indoleacetic acid-induced inhibition. Indoleacetic acid oxidase activity in the soluble fraction was decreased by indoleacetic acid and was restored by hydroxyproline. Most of the indoleacetic acid oxidase activity was located in the electrophoretic zones occupied by two of the peroxidase isoenzymes influenced by indoleacetic acid and hydroxyproline. At least part of the effect of hydroxyproline on auxin-induced elongation of coleoptile tissue may be through control of auxin levels by indoleacetic acid oxidase.     

Promotion of indoleacetic Acid oxidase isoenzymes in tobacco callus cultures by indoleacetic Acid

Indoleacetic acid oxidase in tobacco callus cultures (Nicotiana tabacum L., cv. White Gold) was composed of at least two groups of isoenzymes, which were distinctly different in electrophoretic mobilities and in responses to growth substances. Indoleacetic acid had dual effects; at low concentrations it promoted the development of two fast-migrating indoleacetic acid oxidase isoenzymes, but at high concentrations it increased the level of other indoleacetic acid oxidase isoenzymes with low and moderate electrophoretic mobilities. However, indoleacetic acid was not unique in such effects; 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid were effective at concentrations lower than that of indoleacetic acid.     

The relationship of the peroxidative indoleacetic Acid oxidase system to in vivo ethylene synthesis in cotton

Since peroxidase and manganese have been implicated in both auxin destruction and ethylene production, the effect of auxins and high tissue levels of manganese on the peroxidative indoleacetic acid oxidase system and the internal level of ethylene was determined in cotton (Gossypium hirsutum L. cv. Watson GL-7). The highest level of manganese tested produced manganese toxicity symptoms, including necrotic lesions, accompanied by an increase in internal ethylene levels at about 15 days after treatment initiation. Statistically significant increases in indoleacetic acid oxidase and peroxidase activity were first observed 2 days later and were paralleled by tissue manganese levels above 7.4 milligrams per gram dry weight and internal ethylene levels of 0.77 microliters per liter air. Eight hours after application of 2,4-dichlorophenoxyacetic acid or indoleacetic acid, the internal levels of ethylene were increased to above 6.6 microliters per liter air in cotton plants, and levels of this magnitude were maintained for a 72-hour period of observation. Modification of peroxidase and indoleacetic acid oxidase activity in auxintreated plants definitely occurred well after the elevation of internal ethylene levels. While ethylene levels and indoleacetic acid oxidase activity were increased by both experimental approaches, the earlier appearance of increased ethylene indicates that the peroxidative indoleacetic acid oxidase system in cotton is not involved in ethylene synthesis or that this enzyme is not the rate-limiting factor when ethylene synthesis is increased. Ethylene, as well as auxin destruction, may be involved in some of the long term plant responses to toxic levels of manganese. The findings also suggest that auxin-induced ethylene may play a role in the elevation of peroxidase and indoleacetic acid oxidase activity eventually seen in extracts of plants treated with auxins. The data support the assumption that the enzymatic portion of the indoleacetic acid oxidase system in cotton is a peroxidase.     

Cytokinin-controlled Indoleacetic Acid Oxidase Isoenzymes in Tobacco Callus Cultures

Indoleacetic acid oxidase in tobacco callus tissues (Nicotiana tabacum L., cultivar White Gold) was resolved into seven anionic isoenzymes by polyacrylamide gel disc electrophoresis. Different concentrations of kinetin and zeatin in the presence of indoleacetic acid affected the level of this enzyme, particularly two fast-moving isoenzymes, A₅ and A₆. The optimal concentration of kinetin was 0.2 μm; increasing concentrations above this level progressively lowered the total activity of indoleacetic acid oxidase and repressed the development of isoenzymes A₅ and A₆. Actinomycin D and cycloheximide inhibited the development of these two isoenzymes under the influence of 0.2 μm kinetin, suggesting a requirement for RNA and protein synthesis. The cytokinin-promoted indoleacetic acid oxidase isoenzymes A₅ and A₆ increased with time and paralleled the dry weight increase of tobacco callus tissues, but the total activity of indoleacetic acid oxidase per unit dry weight of tobacco callus varied with time depending on the stage of plant growth.     

Early effects of boron deficiency on indoleacetic Acid oxidase levels of squash root tips

The indoleacetic acid (IAA) oxidase activity of root tips of boron-sufficient, -deficient, recovering, and IAA-treated boron-sufficient squash plants (Cucurbita pepo L.) was determined. Apical and subapical root sections displayed an increase in IAA oxidase activity between 6 and 9 hours after boron was withheld, and after 24 hours the activity of the apical sections showed a 20-fold increase over +B controls. Root elongation of -B plants was inhibited before an increase in oxidase activity could be detected. Roots of plants subjected to 12 hours of -B treatment and then transferred to +B treatment for recovery regained normal elongation rates and oxidase activity within 18 to 20 hours. IAA treatment of +B plants increased IAA oxidase activity of apical and subapical root sections and also inhibited root elongation and caused symptoms similar to -B treatments.     

Changes in Indoleacetic Acid Oxidase Activity Associated with Plant Water Potential

The effect of plant water potential on the activity of indoleacetic acid oxidase was examined. It was found that with increasing plant water deficit the activity of indoleacetic acid oxidase increased. Higher activies of this enzyme are known to be associated with older tissues and lower endogenous auxin levels. It is suggested that while water stress may adversely affect a variety of physiological processes, increases in the activity of indoleacetic acid oxidase may provide plants with a drought adaption mechanism.     

Effects of Pargyline on Mitochondrial Amine Oxidase Activity, Indoleacetic Acid Synthesis and Growth of Crown-Gall Tumor Callus

Vinca rosea L. crown-gall tumor callus tissue cultures treated with N-benzyl-N methyl propargylamine (pargyline) exhibited a decrease in the level of endogenous indoleacetic acid from 0.42 μg/mg of protein to less than 0.30 μg/mg of protein. A simultaneous decrease in the specific activity of mitochondrial amine oxidase from 3000 units to less than 250 units at 1.0 μM, 0.01 mM, 0.1 mM and 1.0 mM pargyline, suggested a relationship between amine oxidase function and indoleacetic acid synthesis. Tryptamine incorporation into indoleacetic acid was also decreased at these concentrations. Pargyline inhibited tumor callus growth significantly (based on fresh weight measurements) at the highest concentration, 1.0mM. These data support the hypothesis of a coordinate metabolic system linking mitochondrial amine oxidase activity and indole acetic acid synthesis. Inhibitory action of pargyline on the enzyme is reflected in reduced indoleacetic acid levels and, ultimately, in reduced callus growth rates.     

The Promotion of Indole-3-acetic Acid Oxidation in Pea Buds by Gibberellic Acid and Treatment

Terminal buds of dark-grown pea (Pisum sativum) seedlings have an indole-3-acetic acid oxidase which does not require Mn(2+) and 2,4-dichlorophenol as cofactors. Oxidase activity is at least 50 times higher in buds of tall peas than in dwarf seedlings. Administration of gibberellic acid to dwarf peas stimulates both growth and indoleacetic acid oxidase activity to the same levels as in tall seedlings. By contrast, indoleacetic acid oxidation assayed in the presence of Mn(2+) and 2,4-dichlorophenol proceeds at similar rates regardless of gibberellin application. Treatment of tall peas with the growth retardant AMO-1618 reduces growth and oxidase activity. Such treated seedlings are indistinguishably dwarf. The enzyme does not appear to be polyphenol oxidase, nor do the results suggest that reduced activity in dwarf buds is due to higher levels of a dialyzable inhibitor. The peroxidative nature of the oxidase is probable.     

Peroxide Levels and the Activities of Catalase, Peroxidase, and Indoleacetic Acid Oxidase during and after Chilling Cucumber Seedlings

The activities of catalase, peroxidase, indoleacetic acid (IAA) oxidase and peroxide levels in cucumber plants during and after chilling were determined. During 96 hours at 5 C and 85% relative humidity, catalase activity declined, IAA oxidase activity increased, and peroxide concentrations increased. Peroxidase activity was not affected by chilling. When chilled plants were returned to 25 C to recover, enzyme activities and peroxide concentration were restored to their prechilling levels. The increase in peroxide and IAA oxidase activity may inactivate or destroy IAA and thus retard growth.     

Dormancy and germination in axillary turions ofHydrilla verticillata

Effects of environmental conditions and growth regulators on release from dormoncy of axillary turions inHydrilla verticillata were investigated. Coll treatment at 2 C for 33 days produced the most complete release from dormancy. One week of 2 C treatment was sufficient for the germination; however, longer cold periods produced more rapid growth in shoot or root lengths as well as a shorter lag time for germination. Dormancy in turions could be broken by a photoperiod of 16 hr but not by on of 8 or 12 hr, nor by continuous lighting. When a cold treatment was applied turions grew out in response to all of the photoperiodic conditions. Red and far-red irradiation during the incubation after a cold treatment promoted gremination; blue and green light markedly inhibited the germination. At 10⁻⁴ and 10⁻⁵ M, gibberellic acid broke dormancy of non-cold treated turions, but was toxic at 10⁻⁴ M to the development after germination. Gibberellic acid promoted growth of cold treated turions even at 10⁻⁶ M. Indoleacetic acid at 10⁻⁴, 10⁻⁵ and 10⁻⁶ M induced outgrowth of both non-cold treated and cold treated turions. Apparently normal growth and development was observed in a high concentration of indoleacetic acid.     

The effect of water stress on indoleacetic Acid oxidase in pea plants

Activity of indoleacetic acid oxidase was shown to increase following a period of water stress. Two fractions of indoleacetic acid oxidase were extracted from plant extracts. Similarly, two protein peaks (determined by ultraviolet absorption) were isolated. One peak, associated with an indoleacetic acid oxidase peak, increased following water stress. The second peak, not associated with extractable indoleacetic acid oxidase, decreased after water stress. The results are discussed in terms of general growth effects.     

The Regulatory Role of the Embryo on the Development of Isocitrate Lyase Activity during Germination of Ponderosa Pine Seeds

The specific activity of isocitrate lyase rapidly increased in the megagametophytic tissue of cold-stratified seeds of ponderosa pine (Pinus ponderosa Laws) prior to and after germination. When the embryo was removed at germination, isocitrate lyase activity continued to develop. However, in the total absence of the embryo, only a small increase in the specific activity of the enzyme was observed. The development of the enzyme was inhibited by cycloheximide, actinomycin D and abscisic acid. The embryo produced an unidentified factor which enhanced the development of isocitrate lyase activity in the megagametophytic tissue. This embryo factor could not be replaced by the hormones indoleacetic acid (IAA), gibberellic acid (GA₃) or benzylaminopurine (BA). Indoleacetic acid had little effect upon enzyme development. Gibberellic acid and benzylaminopurine inhibited isocitrate lyase development in the megagametophytic tissue of the seed.     

Optimum Conditions for Indoleacetic Acid Oxidase Extraction from Betula Leaves

This report deals with total extraction and activation of soluble indoleacetic acid oxidase from Betula alleghaniensis leaves as affected by different buffers, varying pH, phenol binder, detergent, plus volume and time parameters. For all buffers and pH levels tested, only tris pH 8 gave a high activity. This result was not a pH effect, since a wide-range, citrate-phosphate buffer at pH 8 gave a very low activity. Addition of a neutral detergent, Triton X-100, to all buffers gave considerable activity in every case. Most activity with Triton X-100 occurred at pH 6 and least at pH 8 regardless of buffer composition. A phenol binder, polyvinylpyrollidone, increased activity also, but less than the detergent Triton X-100. Both of these compounds in combination gave an additive effect and the highest measure of enzyme activity. Further increases in measurable indoleacetic acid oxidase activity were obtained by using the best combination of these factors to determine the optium tissue: buffer ratio and optimum soaking time. Increases in activity of 70 and 60%, respectively, were achieved.     

Liver alcohol oxidizing systems and gluconeogenic enzyme activities after long term ethanol application in cold exposed guinea pigs

The effects of 4-weeks ethanol application (20% ethanol, w/w, 2 g X kg-1 on the alcohol oxidizing systems and gluconeogenic enzyme activities of the liver in guinea pigs kept in the cold (+4 degrees C) and at room temperature (+20 degrees C) were studied. The controls were guinea pigs reared at room temperature or in a cold environment without ethanol. The study showed a significant increase (1.5-fold) in liver microsomal cytochrome P-450 after chronic ethanol treatment at room temperature, but not in a cold environment. Microsomal NADPH oxidase activity did not significantly change in any group. Ethanol treatment in a cold environment resulted in a significant increase in liver mitochondrial cytochromes, aa3 and c+c1, and at room temperature in cyt aa3. The activities of total liver homogenate alcohol dehydrogenase or catalase did not change after chronic ethanol treatment. The activity of liver fructose-1.6-diphosphatase showed a significant ethanol induced decrease at room temperature, an effect not observed in the cold environment. Ethanol increased glucose-6-phosphatase activity in the cold, but not at room temperature. In conclusion, the stimulation of liver mitochondrial cytochromes and microsomal cyt P-450 as a consequence of chronic ethanol treatment indicated an increased oxidation capacity for ethanol. The stimulation of glucose-6-phosphatase in a cold environment might be responsible for increasing glucose for heat production after chronic ethanol treatment in cold adapted animals.     

Indoleacetic Acid Oxidase: A Dual Catalytic Enzyme?

The isolation of a unique enzyme capable of oxidizing indoleacetic acid, but devoid of peroxidase activity, has been reported for preparations from tobacco roots and commercial horseradish peroxidase. Experiments were made to verify these results using enzyme obtained from Betula leaves and commercial horseradish peroxidase. Both indoleacetic acid oxidase and guaiacol peroxidase activity appeared at 2.5 elution volumes from sulfoethyl-Sephadex. These results were obtained with both sources of enzyme. In no case was a separate peak of indoleacetic acid oxidase activity obtained at 5.4 elution volumes as reported for the tobacco enzyme using the same chromatographic system. Both types of activity, from both sources of enzyme, also eluted together during gel filtration. Successful column chromatography of Betula enzyme was dependent upon previous purification by membrane ultrafiltration. These results indicate indoleacetic acid oxidase activity and guaiacol peroxidase activity are dual catalytic functions of a single enzyme.     

Decreased particulate NADH oxidase activity in Bacillus subtilis spores after polymyxin B treatment

The activities of several enzymes of polymyxin B-treated dormant and germinated spores of Bacillus subtilis were examined. The particulate NADH oxidase of the antibiotic-treated spores showed considerably lower specific and total activities compared with those of untreated ones. The specific and total NADH oxidase activities of untreated spores increased 12- and 15-fold respectively during germination, whereas increases during germination of polymyxin B-treated spores were inhibited. The specific and total activities of particulate NADH cytochrome c reductase of dormant spores were decreased by polymyxin B treatment in almost the same proportion as those of the particulate NADH oxidase. The specific activity of NADH dehydrogenase of dormant spores remained unchanged after antibiotic treatment but the total activity fell considerably. The activities of other enzymes examined were similar for untreated dormant and germinated spores and antibiotic-treated spores. The respiration of polymyxin B-treated dormant spores was inhibited at the same time as the start of germination. Morphologically, polymyxin B-treated dormant spores lost a laminar structure of the cortex and details of the spore protoplast. The inhibitory mechanism of particulate NADH oxidase activity of polymyxin B-treated dormant spores is discussed.     

Changes in indoleacetic Acid oxidase isoenzymes in tobacco tissues after treatment with 2,4-dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acid had a multiple effect on the development of indoleacetic acid oxidase isoenzymes in tobacco callus tissues (Nicotiana tabacum, cv. White Gold) cultured in vitro, and the development of these isoenzymes was differentially associated with growth promotion or inhibition depending on the concentration of 2,4-dichlorophenoxyacetic acid. At low concentrations (0.1 to 1 μm) it promoted the development of a fast migrating isoenzyme A₅ accompanied by stimulation of a tumor-type growth. At high concentrations (10 to 100 μm), it inhibited the development of the fast migrating isoenzymes but promoted a sharp rise in others with slower electrophoretic mobilities, which was accompanied by growth inhibition. The implications are that 2,4-dichlorophenoxyacetic acid might alter the level of endogenous auxins through its dual effects on the oxidase isoenzyme system.     

光叶楮扦插生根的吲哚乙酸氧化酶、多酚氧化酶、过氧化物酶活性变化研究

对光叶楮扦插生根过程中吲哚乙酸氧化酶（IAAO）、多酚氧化酶（PPO）、过氧化物酶（POD）3种酶进行了动态跟踪分析。结果表明：IAAO活性在扦插初期逐渐上升,第10d上升到高峰,之后下降再上升,第30d达到新高峰,然后迅速下降;前25d POD活性变化规律与IAAO相似,但30d以后活性一直上升;PPO活性在扦插前期缓慢上升,第20d上升到了最高点,此后变化不大。还研究了IAAO、PPO、POD与不定根的发生和发展关系,认为光叶楮扦插生根可分为愈伤组织形成期、根诱导期和根的伸长期3个阶段,愈伤组织形成期3种酶活性都呈上升趋势,根诱导期IAAO和POD的活性达到高峰;而根伸长期IAAO和POD活性下降,PPO活性上升。     

Embryo Development in Ripe Seeds of Eranthis hiemalis and its Relation to Gibberellic Acid

The ripe seeds of Eranthis hiemalis (L.) Salisb., the winter aconite, contain undeveloped embryos. At 20–25°C the embryos grow only little, and the seeds do not germinate. Rapid embryo development starts if the seeds, after 3 weeks of “after-ripening” at 20–25°C, are placed at low temperature, 3–4°C; germination then takes place after 2–3 months, Embryo development without germination occurs when the seeds are placed in gibberellic acid solutions at 20–25°C. Embryo development is inhibited at low temperature by the specific inhibitor of gibberellin biosynthesis, 2-chlorethyl cholin chloride, but is restored by the simultaneous addition of gibberellic acid. It is suggested that one early effect of the cold is to bring about a synthesis of gibberellin.     

Cinnamic Acid Increases Lignin Production and Inhibits Soybean Root Growth

Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean (Glycine max) roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H) reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment. Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth.