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Abstract

Grasses producing trans-aconitic acid, a geometric isomer of cis-aconitic acid, are often used in Glycine max rotation systems. However, the effects of trans-aconitic acid on Glycine max are unknown. We conducted a hydroponic experiment to evaluate the effects of 2.5–10 mM trans-aconitic acid on Glycine max growth and photosynthesis. The results revealed that the enhanced H2O2 production in the roots increased the membrane permeability and reduced the water uptake. These effects culminated with a reduced stomatal conductance (gs), which seems to be the main cause for a decreased photosynthetic rate (A). Due to low gs, the limited CO2 assimilation may have overexcited the photosystems, as indicated by the high production of H2O2 in leaves. After 96 h of incubation, and due to H2O2-induced damage to photosystems, a probable non-stomatal limitation for photosynthesis contributed to reducing A. This is corroborated by the significant decrease in the quantum yield of electron flow through photosystem II in vivo (ΦPSII) and the chlorophyll content. Taken together, the damage to the root system and photosynthetic apparatus caused by trans-aconitic acid significantly reduced the Glycine max plant growth.

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... Method or Approach References microbial production of itaconic acid Aspergillus terreus decarboxylation of CAA [43][44][45] microbial production of itaconic acid Ustilago maydis decarboxylation of TAA [43,[46][47][48] Pseudomonas sp. use as sole carbon source isomerization of TAA to CAA for TCA cycle [49] fermentation inhibitor in Saccharomyces cerevisiae, pH-dependent [50][51][52] nematocidal activity Meloidogyne incognita [53] anti-leishmanial activity Leishmania donovani [54,55] regulation of TCA cycle TAA-based inhibition of aconitase [7,56,57] antifungal defense in plants methyl-TAA acts as a phytoalexin [58] antifeedant involved in resistance of some plants to Nilaparvata lugens [59][60][61][62] defense against aluminum toxicity organic acid chelation of Al [5,6] anti-inflammatory activity inhibition of TNF-α release by monocytes [63][64][65] antioxidant activity DPPH assay and nanoliposomes [66][67][68] inhibitor of Glycine max Increased H 2 O 2 in roots and reduced water uptake [69] inhibitor of quorum sensing ligand inhibitor of PleD [70] 3. ...
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Book
This book provides the reader relevant information about actual knowledge about the process of allelopathy, covering all aspects from the molecular to the ecological level. Special relevance is given to the physiological and ecophysiological aspects of allelopathy. Several ecosystems are studied and methodological considerations are taken into account in several different chapters. The book has been written to be useful both for Ph.D. students and for senior researchers, so the chapters include all necessary information to be read by beginners, but they also include a lot of useful information and discussion for the initiated.
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Wheat seedlings (Triticum aestivum) grown on single salt solutions were analyzed for trans-aconitate and aconitate isomerase to determine the possible relationship between them and to determine if they might be related to the incidence of grass tetany. The trans-aconitate activity at the end of a two-day growth period and changes in trans-aconitate activity during this period varied widely and were related to the cation but not the anion of the single salt solution. Aconitate isomerase activity did not vary as much as trans-aconitate or change in trans-aconitate content, and was not closely correlated with the trans-aconitate content. Analysis of diverse species and tissues for aconitate isomerase and trans-aconitate showed that the presence of aconitate isomerase was necessary for appreciable trans-aconitate accumulation. We conclude that the activity of aconitate isomerase does not control trans-aconitate content but that its presence is necessary for any significant accumulation of trans-aconitate. Keywords: Wheat; grass tetany; aconitate; aconitate isomerase; organic acids
Article
Chemical manipulation of the phytohormone system involves the use of herbicides for weed control in modern crop production. In the latter case, only compounds interacting with the auxin system have gained practical importance. Auxin herbicides mimic the overdose effects of indole-3-acetic acid (IAA), the principal natural auxin in higher plants. With their ability to control, particularly, dicotyledonous weeds in cereal crops, the synthetic auxins have been among the most successful herbicides used in agriculture. A newly discovered sequential hormone interaction plays a decisive role in their mode of action. The induction of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase in ethylene biosynthesis is the primary target process, following auxin herbicide signalling. Although the exact molecular target site has yet to be identified, it appears likely to be at the level of auxin receptor(s) for perception or signalling, leading ultimately to species- and organ-specific de novo enzyme synthesis. In sensitive dicots, ethylene causes epinastic growth and tissue swelling. Ethylene also triggers the biosynthesis of abscisic acid (ABA), mainly through the stimulated cleavage of xanthophylls to xanthoxal, catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). ABA mediates stomatal closure which limits photosynthetic activity and biomass production, accompanied by an overproduction of reactive oxygen species. Growth inhibition, senescence and tissue decay are the consequences. Recent results suggest that ethylene-triggered ABA is not restricted to the action of auxin herbicides. It may function as a module in the signalling of a variety of stimuli leading to plant growth regulation. An additional phenomenon is caused by the auxin herbicide quinclorac which also controls grass weeds. Here, quinclorac induces the accumulation of phytotoxic levels of cyanide, a co-product of ethylene, which ultimately derives from herbicide-induced ACC synthase activity in the tissue. Phytotropins are a further group of hormone-related compounds which are used as herbicides. They inhibit polar auxin transport by interacting with a regulatory protein, the NPA-binding protein, of the auxin efflux carrier. This causes an abnormal accumulation of IAA and applied synthetic auxins in plant meristems. Growth inhibition, loss of tropic responses and, in combination with auxin herbicides, synergistic effects are the consequences. KeywordsAbscisic acid (ABA)–1-Aminocyclopropane-1-carboxylic acid (ACC) synthase–Auxin herbicides–Auxin transport–Cyanide–Ethylene–Indole-3-acetic acid (IAA)–Phytotropins–Reactive oxygen species (ROS)
Article
The responses of photosynthetic gas exchange and chlorophyll fluorescence along with changes in carbohydrate and proline levels were studied in cowpea (Vigna unguiculata) during water stress and recovery. Three experiments were conducted under greenhouse and laboratory conditions. Decreased CO2 assimilation rates during water stress were largely dependent on stomatal closure, which reduced available internal CO2 and restricted water loss through transpiration. During the initial phase of stress, photochemical activity was not affected, as revealed by lack of alterations in fluorescence parameters associated with photosystem II (PSII) activity. Development of non-radiative energy dissipation mechanisms was evidenced during stress by increases in non-photochemical quenching and decreases in efficiency of excitation capture by open centers. At an advanced phase of stress, a down-regulation of PSII activity was observed along with some impairment of photochemical activity, as revealed by decreases in the maximum quantum yield of PSII (Fv/Fm). However, this impairment did not limit the overall photosynthetic process, since assimilation rates recovered, upon rewatering, independent of the still present decreased Fv/Fm values. Complete recovery of all gas exchange and fluorescence parameters occurred 3 days after rewatering. However, on the first day after water stress relief, assimilation rates only partially recovered in spite of the availability of internal CO2, suggesting some non-stomatal limitation of photosynthesis. Accordingly, the downregulation of PSII activity observed during stress persisted at this time. Our results on carbohydrate metabolic changes revealed an accumulation of soluble sugars in water-stressed leaves, which also persisted for 1 day after rewatering. This finding suggest a transient end-product inhibition of photosynthesis, contributing to a minor non-stomatal limitation during stress and initial phase of recovery. Increases in proline level were small and their onset was delayed after stress imposition, so that it may rather be a consequence and not a stress-induced beneficial response.
Article
In this work the differential response of adult and young leaves from pea (Pisum sativum L.) plants to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) (23 mm) applied by foliar spraying was investigated. The concentration of 2,4-D (23 mm) and the time of treatment (72 h) were previously optimized in order to visualize its toxic effects on pea plants. Under these conditions, the herbicide induced severe disturbances in mesophyll cells structure and proliferation of vascular tissue in young leaves and increased acyl-CoA oxidase (ACX), xanthine oxidase (XOD) and lipoxygenase (LOX) activities in young leaves, and only ACX and LOX in adult leaves. This situation produced reactive oxygen species (ROS) over-accumulation favoured by the absence of significant changes in the enzymatic antioxidants, giving rise to oxidative damages to proteins and membrane lipids. An increase of ethylene took place in both young and adult leaves and the induction of genes encoding the stress proteins, PRP4A and HSP 71,2, was observed mainly in young leaves. These results suggest that ROS overproduction is a key factor in the effect of high concentrations of 2,4-D, and ROS can trigger a differential response in young and adult leaves, either epinasty development in young leaves or senescence processes in adult tissues.
Article
Forage samples were obtained from three wheat and rye mixed pastures (replications) from December 1979, to April 1980 (140 d), while they were being grazed by mature cows at the Southwestern Livestock and Forage Research Station, El Reno, Oklahoma. These samples were taken three times during December, twice monthly in January and February and weekly in March and April. Samples were analyzed for dry matter, ash, N, K, Ca, Mg, P, ash alkalinity, aconitic, malic and citric acids, total lipids, NO3-N, Na and total nonstructural carbohydrates (TNC). In vitro digestibility was also determined. The N:TNC ratio, estimated plasma Mg levels and K:(Ca + Mg) ratio (tetany ratio) were calculated. On d 105 (March 19), 16% (five of 32 head) of the cows developed tetany. At tetany, the forage K, protein, digestibility, ash alkalinity, aconitic acid and total lipids increased suddenly and markedly. Forage dry matter, TNC and ash decreased. Forage Ca and Mg were slightly below or equal to the animals' requirements and remained relatively constant during the period of tetany. Forage P increased about 2 wk before tetany and decreased after tetany occurred. The levels of forage NO3-N and Na did not appear to be related to the incidence of tetany. The N:TNC ratios exceeded .4 immediately before tetany and two sampling periods thereafter. The estimated plasma Mg levels were lowest at tetany and shortly thereafter and tetany ratio exceeded 2.2 during most of the study, with peaks of 3.2 in December, at tetany and in early April.
Article
Allelochemicals play an important role in explaining plant growth inhibition in interspecies interactions and in structuring the plant community. Five aspects of allelochemicals are discussed from an ecophysiological perspective: (i) biosynthesis, (ii) mode of release, (iii) mode of action, (iv) detoxification and prevention of autotoxicity, and (v) joint action of allelochemicals. A discussion on identifying a compound as an allelochemical is also presented.
Article
Juglone is phytotoxic, but the mechanisms of growth inhibition have not been fully explained. Previous studies have proposed that disruption of electron transport functions in mitochondria and chloroplasts contribute to observed growth reduction in species exposed to juglone. In studies reported here, corn and soybean seedlings grown in nutrient solution amended with 10, 50, or 100 microM juglone showed significant decreases in root and shoot dry weights and lengths with increasing concentrations. However, no significant differences in leaf chlorophyll fluorescence or CO2-dependent leaf oxygen evolution were observed, even in seedlings that were visibly affected. Disruption of root oxygen uptake was positively correlated with increasing concentrations of juglone, suggesting that juglone may reach mitochondria in root cells. Water uptake and acid efflux also decreased for corn and soybean seedlings treated with juglone, suggesting that juglone may affect metabolism of root cells by disrupting root plasma membrane function. Therefore, the effect of juglone on H+-ATPase activity in corn and soybean root microsomes was tested. Juglone treatments from 10 to 1000 microM significantly reduced H+-ATPase activity compared to controls. This inhibition of H+-ATPase activity and observed reduction of water uptake offers a logical explanation for previously documented phytotoxicity of juglone. Impairment of this enzyme's activity could affect plant growth in a number of ways because proton-pumping in root cells drives essential plant processes such as solute uptake and, hence, water uptake.
Article
Tomato (Lycopersicon esculentum) seedlings were grown in four cadmium (Cd) levels of 0-10 microM in a hydroponic system to analyze the antioxidative enzymes, Cd concentration in the plants, and the interaction between Cd and four microelements. The results showed that there was a significant increase in malondialdehyde (MDA) concentration, and superoxide dismutase (SOD) and peroxidase (POD) activities in the plants subjected to 1-10 microM Cd. This indicates that Cd stress induces an oxidative stress response in tomato plants, characterized by an accumulation of MDA and increase in activities of SOD and POD. Root, stem and leaf Cd concentrations increased with its exposure Cd level, and the highest Cd concentration occurred in roots, followed by leaves and stems. A concentration- and tissue-dependent response was found in the four microelement concentrations to Cd stress in the tomato leaves, stems and roots. Regression analysis showed that there was a significantly negative correlation between Cd and Mn, implying the antagonistic effect of Cd on Mn absorption and translocation. The correlation between Cd and Zn, Cu and Fe were inconsistent among leaves, stems and roots.
Article
Trans-aconitate synthesis via citrate dehydrase was determined in crude extracts of maize (Zea mays L.) coleoptiles. Two molecular forms of this enzyme were purified by substrate-specific elution from DEAE-cellulose, ammonium sulfate precipitation, and gel filtration. Each molecular form migrates as a single band in isoelectric focusing. Gel filtration and sodium dodecyl sulfate electrophoresis provided evidence that one enzyme form is composed of four 80,000-dalton subunits while the other is composed of two 60,000-dalton subunits. There was no evidence of proteolytic conversion of the large to the small molecular weight form when the former was incubated with either the 15,000(g) supernatant or with proteases. The data indicate that the two molecular forms of citrate dehydrase are isozymes.
Article
The role of brassinosteroids (BRs) in plant function has been intensively studied in the last few years. Mutant analysis has demonstrated that the ability to synthesize, perceive and respond to BRs is essential to normal plant growth and development. Several key elements of BR response have been identified using both genetic and biochemical approaches, and molecular models that parallel Wingless (Wnt), transforming growth factor beta (TGF beta) and receptor tyrosine kinase (RTK) signalling in animals have been proposed. Many studies have demonstrated the role of BRs, alone and in interaction with other plant hormones, in processes such as cell elongation and seed germination. In contrast, little is known about how the sensing of BRs is connected to specific physiological responses such as stress resistance. There remain many open questions about how these connections are made.
Article
trans-Aconitate ion, an inhibitor of the tricarboxylic acid cycle, was identified in range grasses as trans-aconitic acid, which was isolated in crystalline form. It occurs in surprisingly high concentrations in early-season forage grasses. Dry-weight concentrations of trans-aconitate vary with season and species; concentrations of between I and 2.5 percent are common in mixed pasture grasses, but are higher in certain species such as Hordeum leporinum (3.5 percent) and Phalaris tuberosa var. stenoptera (4.2 percent). Leaves of western larkspur (Delphinium hesperium) contain 12.2 percent trans-aconitate. trans-Aconitate may be partially responsible for nutritional disorders, such as grass tetany (hypomagnesemia), that occur in grazing cattle in early spring.
Article
The use of chlorophyll fluorescence to monitor photosynthetic performance in algae and plants is now widespread. This review examines how fluorescence parameters can be used to evaluate changes in photosystem II (PSII) photochemistry, linear electron flux, and CO(2) assimilation in vivo, and outlines the theoretical bases for the use of specific fluorescence parameters. Although fluorescence parameters can be measured easily, many potential problems may arise when they are applied to predict changes in photosynthetic performance. In particular, consideration is given to problems associated with accurate estimation of the PSII operating efficiency measured by fluorescence and its relationship with the rates of linear electron flux and CO(2) assimilation. The roles of photochemical and nonphotochemical quenching in the determination of changes in PSII operating efficiency are examined. Finally, applications of fluorescence imaging to studies of photosynthetic heterogeneity and the rapid screening of large numbers of plants for perturbations in photosynthesis and associated metabolism are considered.
Article
Calcium has been suggested as an important mediator of gravity signaling transduction within the root cap statocyte. In a horizontally-placed root, it is redistributed in the direction of the gravity vector (i.e. it moves downward) and its redistribution is closely correlated with auxin downward movement. However, the involvement of calcium in the regulation of ethylene-induced epinasty and auxin movement is not known. In this report, we examined the involvement of calcium in lateral auxin transport during ethylene-induced epinasty in an effort to understand the relationship among calcium, auxin, and ethylene. Ethylene-induced epinasty was further stimulated by exogenously applied Ca2+, the calcium effect being the strongest among divalent cations tested. Pretreatment with NPA, an auxin transport inhibitor, negated the promotive effect of calcium ions on the petiolar epinasty. Ethylene caused redistribution/differential accumulation of 45Ca2+ toward the morphologically lower (abaxial) side of the leaf petioles, an effect opposite to that of 14C-IAA redistribution. Verapamil, a Ca2+ channel blocker, inhibited ethylene-induced epinasty, as well as the redistribution of 14C-IAA and 45Ca2+. When the petiole was inverted in the presence or absence of ethylene, the direction of 45Ca2+ differential accumulation was still toward the morphologically abaxial side of the petiole during epinastic movement regardless of gravitational direction. These results suggest that gravity-insensitive, ethylene-induced Ca2+ redistribution and accumulation toward the abaxial side are closely coupled to the adaxial auxin redistribution/accumulation and, in turn, to the petiolar epinasty.
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