Gibberellin A3 Causes a Decrease in the Accumulation of mRNA for ACC Oxidase and in the Activity of the Enzyme in Azuki Bean (Vigna angularis) Epicotyls

Differential screening, aimed at the isolation of cDNA clonesof mRNAs whose accumulation is influenced by GA₃, resulted inthe isolation of a cDNA clone of an mRNA whose level was decreasedby GA₃ in segments of epicotyls of Vigna angularis. The putativeprotein encoded by this cDNA resembled the 1-aminocyclopropane-l-carbox-ylateoxidases (ACC oxidases) identified in other plant species (about80% homology at the amino acid level). Thus, the correspondinggene was designated AB-ACO1 (azuki bean ACC oxidase). GA₃ alsodecreased the activity of ACC oxidase in azuki bean epicotyls,but it did not decrease the rate of ethylene evolution. In fact,GA₃ increased the rate of ethylene evolution and the level ofACC. Thus, GA₃ seemed to increase the production of ethyleneby promoting the synthesis of ACC. (Received January 10, 1997; Accepted July 31, 1997)     

The Extracellular Acidic and Basic Pathogenesis-Related Proteins of Soybean Induced by Viral Infection

Seventeen major host-encoded pathogenesis related (PR)-proteins have been found in intercellular fluids of necrotic virus-infected soybean leaves. None of them was present in fluids of healthy controls. By native and SDS-denaturing polyacrylamide gel electrophoresis, ten major acidic PR-proteins have been identified and classified on the basis of their molecular weight in three groups: group 1 included four proteins of 16–17 Kd; group 2, three proteins of 26 Kd; group 3, three proteins of 32 Kd. Seven PR-proteins were basic, and were classified in three groups: group 1 included three proteins of 16 Kd; group 2, one protein of 23 Kd; group 3, three proteins of 32 Kd. As found for tobacco and potato, soybean PR-protein patterns show high number of acidic and basic proteins.     

Cloning of a Complementary DNA that Encodes an Acidic Chitinase which is Induced by Ethylene and Expression of the Corresponding Gene

A complementary DNA encoding an ethylene-inducible acidic chitinaseof azuki bean (Vigna angularis) was isolated, and its completenucleotide sequence was determined. The nucleotide and deducedamino-acid sequence were very similar to those of an acidicchitinase from cucumber leaves that had been infected with tobacconecrosis virus. The mRNA for the acidic chitinase was not detectedin leaves of azuki bean that had not been treated with ethylene,but it appeared 3 h after initiation of treatment with ethyleneand its level gradually increased over a period of 19 h. ThemRNA also accumulated in response to salicylate or wounding.The expression of the gene in response to wounding was suppressedby 2,5-norbornadiene, but that in response to salicylate wasnot affected by this inhibitor. (Received May 19, 1992; Accepted November 2, 1992)     

Induction of Phenylalanine Ammonia-Lyase Activation and Isoflavone Glucoside Accumulation in Suspension-Cultured Cells of Red Bean, Vigna angularis, by Phytoalexin Elicitors, Vanadate, and Elevation of Medium pH

Treatment of suspension-cultured cells of red bean, Vigna angularis,with nigeran resulted in an accumulation of isoflavone glucosides,such as daidzein 7-O-ß-D-glucoside, daidzein 7,4'-di-O-ß-D-glucoside,and 2'-hydroxydaidzein 7,4'-di-O-ß-D-glucoside, whichwas accompanied by a transient increase in the activity of phenylalanineanimonia-lyase (PAL). Similar effects were also seen with otherphytoalexin elicitors, such as RNase A and cell wall componentsof Phytophthora megasperma var. sojae. Interestingly, the accumulation of isoflavone glucosides andthe transient increase in PAL activity were induced also byvanadate, a specific inhibitor of plasma membrane adenosinetriphosphatase. K₃PO₄ showed similar effects, but this was ascribedto the elevation of medium pH caused by adding this basic salt.In fact, merely raising the pH of the medium was found to besufficient for the induction of PAL activity. Experiments usinginhibitors showed that the induction depends on RNA and proteinsyntheses. The results are discussed in relation to the possiblemechanism of action of phytoalexin elicitors. ¹ Present address: Laboratory of Biochemistry, Faculty of Agriculture,Nagoya University, Furocho, Chikusa, Nagoya 464, Japan.     

Effects of Uniconazole on Leaves Photosynthesis,Root Distribution and Yield of Mung Bean (Vigna radiata)

Journal of Plant Growth Regulation - Uniconazole was a plant growth retardant with effect of regulating plant growth and development, however, there were very few studies on its application to mung...     

Contrasting Effects of the Cotton Defoliant Thidiazuron and Aminoethoxyvinylglycine,an Inhibitor of Ethylene Formation,on Stomatal Aperture and on Ethylene Formation in Bean (Phaseolus vulgaris) Leaves

The cotton defoliant, thidiazuron, 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea stimulated ethylene formation in primary leaves of Phaseolus vulgaris var. Favorit, three to eight days after spraying. Aminoethoxyvinylglycine (AVG), an inhibitor of ethylene formation, delayed this ethylene outburst by two to three days when sprayed together with the defoliant. Under conditions of dryness, thidiazuron inhibited the stomatal closure of bean leaves. Spraying with AVG counteracted this effect of thidiazuron on the stomates and caused a partial and reversible closure ca 1 day after spraying.     

The Effects of pH on a Periphyton Community in an Acidic Wetland, USA

Despite the importance of peatlands, the algal ecology of peatlands and the periphyton communities which are abundant in these habitats are relatively understudied. We performed an in situ manipulation of pH in an intermediate fen in northern lower Michigan in order to examine how hydrogen ion concentrations structure an epiphytic algal community. Levels of pH were manipulated in enclosures from the control level (pH = 5) to an acid treatment (pH = 4) by adding H₂SO₄ and a neutral treatment (pH = 7) by adding NaOH. Algal communities growing on sections of Chamaedaphne calyculata (L.) Moench stems were examined after 22 days of colonization. Chlorophyll a concentration was significantly greater only in the acid treatment (~5.5 mg m⁻²) relative to the control (~3.5 mg m⁻²). Taxa richness was lower in the acid treatment. The algal assemblages were dominated by filamentous green algae and a filamentous taxon, Mougeotia spp., was significantly greater in the acid treatment relative to the control. Increases in Zygnemataceae and Oedogonium spp. most likely account for the higher chlorophyll a in the acid treatment. Most treatment differences were detected in the neutral treatment, including increased abundances of Closterium polystichum Nygaard, Cosmarium sp., Peridinium inconspicuum Lemmermann, and Synedra acus Kütz. Unexpectedly, there was no strong response of the desmid community. These data can be informative in the development of algal monitoring programs in peatlands when assessment of acidification is desired.     

Effects of Ethephon, 1-Aminocyclopropane-1-carboxylic Acid, and Inhibitors of Ethylene Synthesis on the Gravitropically Induced Movement of Mimosa pudica Pulvinus

Primary pulvini of Mimosa pudica L. displaced from their position display gravitropic movements beginning about 15 minutes after their reorientation. Ethephon, an ethylene-releasing compound, and 1-aminocyclopropane-1-carboxylic acid, an intermediate in ethylene biosynthesis, enhance these movements at a concentration as low as 10 nanomolar. Inhibitors of ethylene synthesis (l-α-(2-aminoethoxyvinyl)glycine, (aminooxy)acetic acid, and Co²⁺) reduce the amplitude of the movements. The promotive action of 1-aminocyclopropane-1-carboxylic acid is abolished by l-α-(2-aminoethoxyvinyl)glycine. These results permit one to conclude that ethylene may modify the curvature movement but not the initiation of the gravitropic reaction. With reference to the pulvinus functioning based on turgor variations and ion migrations inside the organ, namely K⁺ acting as the osmoticum, the data suggest that ethylene may act by increasing the membrane permeability to water and/or by altering an ion pump.     

Gas Exchange and Phytoluminography of Single Red Kidney Bean Leaves during Periods of Induced Stomatal Oscillations: A Demonstration of an Integrated, Spatially Resolving Physiometric Technique

This report examines the capabilities of a new approach to the study of gas exchange and electron transport properties of single, intact leaves. The method combines conventional aspects of analysis with an image intensification system that records the spatial distribution of delayed light emission (DLE) over single leaf surfaces. The combined system was used to investigate physiological perturbations induced by exposure of single leaves of Phaseolus vulgaris cv `California Light Red' to a combination of SO₂ (0.5 microliters per liter) and ozone (0.1 microliters per liter). Exposure of one-half of a leaf to this combination induced DLE and stomatal oscillations, but only in the half of the leaf exposed to the combined gases. Examination of phytoluminographs taken during these oscillations revealed distinct leaf patches where the greatest changes in DLE intensity occurred. This phenomenon is interpreted to be evidence that control of stomatal activity of intact plant leaves occurs within discrete leaf areas defined within the vascular network.     

Soybean Lipoxygenase L-4, a Component of the 94-kilodalton Storage Protein in Vegetative Tissues: Expression and Accumulation in Leaves Induced by Pod Removal and by Methyl Jasmonate

A lipoxygenase L-4 gene was isolated from a soybean genomiclibrary. The amino acid sequence of lipoxygenase L-4 is highlyhomologous with the partial amino acid sequence of the 94-kDavegetative storage protein, vsp94, found in paraveinal mesophyllcells in the leaves of depodded soybean plants. No L-4 expressionwas observed in maturing seeds. The L-4 gene is highly expressedin the vegetative tissues of young seedlings, including cotyledons,hypocotyls, roots and primary leaves. L-4 expression followedthe same pattern as lipoxygenase activity in cotyledons peaking3 to 5 days after germination, and returning to a basal levelby 9 days after germination. L-4 gene expression was low inthe roots, stems and leaves of 10-week-old plants. Exposureof 4-week-old plants to atmospheric methyl jasmonate increasedL-4 mRNA in leaves. Continuous pod removal from 7-week-old plantsover a 2 week period resulted in dramatic accumulation of L-4mRNA in leaves. Accumulation of the L-4 protein and three otherlipoxygenase fractions in the leaves of depodded plants wasdemonstrated by ion exchange chromatography. These results indicatethat lipoxygenase L-4 is a component of vsp94. (Received May 31, 1993; Accepted August 9, 1993)     

Signaling Effects of Nitric Oxide, Salicylic Acid, and Reactive Oxygen Species on Isoeuphpekinensin Accumulation in Euphorbia pekinensis Suspension Cells Induced by an Endophytic Fungal Elicitor

Nitric oxide (NO), salicylic acid (SA), and reactive oxygen species (ROS) are important signal molecules that mediate plant resistance reactions and play important roles in secondary metabolism. To research the signal transduction pathway of the endophytic fungal elicitor from Fusarium sp. E5 promoting secondary metabolism in Euphorbia pekinensis suspension cells, the changes in NO, SA, ROS, and isoeuphpekinensin contents in the cells were investigated after elicitor addition to the cell suspension culture. The elicitor did not change H₂O₂ or O₂ ^? contents notably, whereas NO and SA contents were enhanced. Both the NO donator sodium nitroprusside (SNP) and SA enhanced isoeuphpekinensin content in the absence of the fungal elicitor, whereas the NO scavenger cPTIO and SA biosynthesis inhibitor cinnamic acid (CA) inhibited isoeuphpekinensin accumulation in the presence of the elicitor. In addition, cPTIO inhibited SA production induced by the fungal elicitor. CA did not inhibit NO production, but it significantly inhibited isoeuphpekinensin accumulation. The results demonstrated that in Euphorbia pekinensis suspension cells the endophytic fungal elicitor induced increased NO content and SA production, which promoted isoeuphpekinensin accumulation. ROS are clearly not involved in the endophytic fungus–host interaction signaling pathway.     

Regulation of Peroxidase-Dependent Oxidation of Phenolics by Ascorbic Acid: Different Effects of Ascorbic Acid on the Oxidation of Coniferyl Alcohol by the Apoplastic Soluble and Cell Wall-Bound Peroxidases from Epicotyls of Vigna angularis

Intercellular washing fluid (IWF) and washed cell walls obtainedfrom epicotyls of Vigna angularis catalyzed the oxidation ofconiferyl alcohol in the presence of hydrogen peroxide, indicatingthe presence of both soluble and bound peroxidases in the cellwalls. The products of oxidation of coniferyl alcohol were identicalin both cases. Ascorbic acid inhibited the oxidation of coniferylalcohol. The inhibition was due to the rapid reduction of anoxidized intermediate of coniferyl alcohol by ascorbic acid,with resultant regeneration of coniferyl alcohol. However, theinhibitory effects of ascorbic acid were different in the caseof IWF and cell walls. Ascorbic acid completely inhibited theoxidation of coniferyl alcohol by IWF peroxidase as long asascorbic acid was available, whereas the oxidation of coniferylalcohol by cell wall-bound peroxidase was competitively inhibitedby ascorbic acid. Ascorbic acid was present in cell walls andlignin was formed in cell walls during aging of stem. Basedon these results, a possible function for ascorbic acid in theregulation of oxidation of phenolics in cell walls is discussed. (Received March 19, 1993; Accepted May 24, 1993)     

Studies of Rapidly Induced Wound Ethylene Synthesis by Excised Sections of Etiolated Pisum sativum L., cv. Alaska: IV. Requirement of a Water-soluble, Heat-stable Factor

The rate of wound ethylene synthesis was reduced by more than 85% when 9-millimeter subapical sections of etiolated 7-day-old Pisum sativum L., cv. Alaska seedlings were incubated in water during the 26-minute induction period prior to wound ethylene synthesis, but the rate of synthesis was unaffected if sections were incubated in water during the actual synthesis of wound ethylene. The characteristic timing of the wound response was unaffected by either treatment. The ability of various chemical solutions and aqueous plant extracts to alter the rate of wound ethylene synthesis was studied by first incubating subapical pea stem sections in solutions under anaerobic conditions (anaerobiosis delays the induction and synthesis of wound ethylene; Plant Physiol 61: 675-679), and then measuring wound ethylene synthesis after the tissue was transferred to air. Solutions of several reported precursors of ethylene synthesis, such as methionine, homoserine, or propanal, did not reverse the water-caused reduction of wound ethylene synthesis. A water-soluble, heat-stable factor in extracts from pea seedlings, and solutions of 23 nanomolar triacontanol, 10 micromolar kinetin, or 10 micromolar benzyladenine prevented the reduction of wound ethylene synthesis, but were ineffective if administered after an initial 15-minute anaerobic water incubation. This suggested that the active solutions may have only prevented the loss of some ephemeral, though necessary factor, rather than actually containing the substrate or inducer of wound ethylene synthesis. Attempts to isolate and characterize the active fraction from aqueous tissue extracts were unsuccessful. Free radical quenchers, inhibitors of protein synthesis, and rhizobitoxine, an inhibitor of ethylene synthesis from methionine, all reduced wound ethylene synthesis when administered in solutions which previously had maintained wound ethylene synthesis.     

Utilization of Ammonium as a Nitrogen Source : Effects of Ambient Acidity on Growth and Nitrogen Accumulation by Soybean

Dry matter accumulation of plants utilizing NH₄⁺ as the sole nitrogen source generally is less than that of plants receiving NO₃⁻ unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH₄⁺ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH₄⁺ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 ± 0.1 by automatic additions of 0.01 n H₂SO₄ or Ca(OH)₂. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH₄⁺ uptake per gram root dry weight were calculated from these data. Net CO₂ exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO₂ exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH₄⁺ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO₂ exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH₄⁺, which were initially about 50% lower at pH 4.1 than at 6.1, continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.     

Effects of Relaxing Music on Mental Fatigue Induced by a Continuous Performance Task: Behavioral and ERPs Evidence

The purpose of this study was to investigate whether listening to relaxing music would help reduce mental fatigue and to maintain performance after a continuous performance task. The experiment involved two fatigue evaluation phases carried out before and after a fatigue inducing phase. A 1-hour AX-continuous performance test was used to induce mental fatigue in the fatigue-inducing phase, and participants’ subjective evaluation on the mental fatigue, as well as their neurobehavioral performance in a Go/NoGo task, were measured before and after the fatigue-inducing phase. A total of 36 undergraduate students (18–22 years) participated in the study and were randomly assigned to the music group and control group. The music group performed the fatigue-inducing task while listening to relaxing music, and the control group performed the same task without any music. Our results revealed that after the fatigue-inducing phase, (a) the music group demonstrated significantly less mental fatigue than control group, (b) reaction time significantly increased for the control group but not for the music group, (c) larger Go-P3 and NoGo-P3 amplitudes were observed in the music group, although larger NoGo-N2 amplitudes were detected for both groups. These results combined to suggest that listening to relaxing music alleviated the mental fatigue associated with performing an enduring cognitive-motor task.