Serratia sp., an endophyte of Mimosa pudica nodules with nematicidal, antifungal activity and growth-promoting characteristics.

In the present study, the nematicidal activity of an isolated strain of Mimosa pudica nodules was evaluated against the Nacobbus aberrans (J2) phytonymatodes with a mortality of 88.8%, while against the gastrointestinal nematode Haemonchus contortus (L3) and free-living Panagrellus redivivus was 100%. The ability to inhibit the growth of phytopathogenic fungi Fusarium sp., and Alternaria solani, as well as the oomycete Phytophthora capsici, this antifungal activity may be related to the ability to produce cellulases, siderophores and chitinases by this bacterial strain. Another important finding was the detection of plant growth promoter characteristics, such as auxin production and phosphate solubilization. The strain identified by sequences of the 16S and rpoB genes as Serratia sp. is genetically related to Serratia marcescens and Serratia nematodiphila. The promoter activity of plant growth, antifungal and nematicide of the Serratia sp. strain makes it an alternative for the biocontrol of fungi and nematodes that affect both the livestock and agricultural sectors, likewise, candidate as a growth-promoting bacterium.

Auxinic herbicide conjugates with an α-amino acid function: Structural requirements for biological activity on motor cells.

Two Fabaceae exhibiting rapid osmocontractile pulvinar movements were used in this study because this activity is modified by natural auxin and dramatically by 2,4D. A short chain with a carboxylic group being required for auxinic properties, a critical point to analyze is whether the recently synthesized proherbicide ε-(2,4-dichlorophenoxyacetyl)-L-Lys (2-4D-L-Lys) maintains some biological activity despite the increase in length of the chain and the substitution of the carboxyl group by an α-amino acid function. No trace of 2,4D could be detected in the pulvinar tissues treated for 1 h with 2,4D-L-Lys. Complementary approaches (electrophysiology, pH measurements, use of plasma membrane vesicles) suggest that it was less efficient than 2,4D to activate the plasma membrane H+-ATPase (PM-H+-ATPase). However, it modified the various ion-driven reactions of Mimosa pudica and Cassia fasciculata pulvini in a similar way as 2,4D. Additionally, it was much more effective than fusicoccin to inhibit seismonastic movements of M. pudica leaves and, at low concentrations, to promote leaflet opening in dark, indicating that its mode of action is more complex than the only activation of the PM-H+-ATPase. Various substitutions on 2,4D-L-Lys affected its activity in correlation with the molecular descriptor "halogen ratio" of these derivatives. Conjugation with D-Lys also led to a decrease of pulvinar reaction, suggesting that 2,4D-Lys maintains the main signaling properties of 2,4D involved in pulvinar movements providing that the terminal zwitterion is in a suitable orientation. Our data guide future investigations on the effect of 2,4D and 2,4D-L-Lys on the vacuolar pump activity of motor cells.

Characteristic early membrane effects induced by tryptophan in pulvinar motor cells.

Tryptophan at concentrations higher than 0.1 mM, triggered characteristic early physiological effects such as rapid (within 5 min) dose-dependent membrane hyperpolarization in Mimosa pudica motor cells and modification of the time course of the spontaneous proton efflux monitored in the incubation medium of pulvinar tissues. The rapid modifications of the leaf turgor-mediated movements seen on the primary pulvini of M. pudica following a shock and on Cassia fasciculata leaflets during a transition from light to darkness indicate that tryptophan disturbed the ionic migrations involved in the electrophysiological events and in the osmocontractile reaction of the motor cells. These reactions were specific to tryptophan compared to those induced by serine and 5-hydroxytryptophan. The tryptophan mode of action cannot be linked to a direct modification of the plasma membrane H+-ATPase activity as monitored on purified pulvinar plasma membrane vesicles. The tryptophan metabolism-linked products tryptamine and indole also inhibited the motile reactions, activated in a continuous manner the H+ secretion of pulvinar tissues and showed properties of a protonophore and an ATPase activity inhibitor on plasma membrane vesicles, respectively. The specific behavior of tryptophan in the reaction studies here is discussed in light of the previously reported action of phytohormones.

Effect of EDTA and NTA on Arsenic Bioaccumulation and Translocation Using Phytoremediation by Mimosa pudica L. from Contaminated Soils.

This study aimed to investigate the effects of Nitrilotriacetic acid (NTA) and Elthylenediaminetetraacetic acid (EDTA) on the bioaccumulation and translocation of arsenic (As) by Mimosa pudica L. using soils with 5 mg/kg of added As and NTA and EDTA concentrations of 50, 100, and 200 mg/kg. Soil and plant samples were collected every 30-120 days to analyze the As concentrations in the soil, underground part of the plants (root), and aboveground parts of the plants (shoots and leaves). The results showed that the plants with EDTA concentrations of 100 mg/kg had the highest As accumulation. At 120 days, M. pudica L. had a higher accumulation in the underground parts (29.71 mg/kg) than in the aboveground parts (6.32 mg/kg), with statistical significance (p < 0.05). The As translocation factor in the aboveground parts was less than 1, indicating As accumulation in the underground part only. With EDTA concentrations of 50 and 100 mg/kg, M. pudica L. had the highest bioaccumulation potential of As of 8.00 and 8.44, respectively. However, this research did not examine the reaction between As and any growth promoters. Further research should investigate the details of such a reaction at the molecular level, as well as explore how fertilizer factors might affect the As absorption of M. pudica L.

Anaesthetics stop diverse plant organ movements, affect endocytic vesicle recycling and ROS homeostasis, and block action potentials in Venus flytraps.

Background and Aims: Anaesthesia for medical purposes was introduced in the 19th century. However, the physiological mode of anaesthetic drug actions on the nervous system remains unclear. One of the remaining questions is how these different compounds, with no structural similarities and even chemically inert elements such as the noble gas xenon, act as anaesthetic agents inducing loss of consciousness. The main goal here was to determine if anaesthetics affect the same or similar processes in plants as in animals and humans. Methods: A single-lens reflex camera was used to follow organ movements in plants before, during and after recovery from exposure to diverse anaesthetics. Confocal microscopy was used to analyse endocytic vesicle trafficking. Electrical signals were recorded using a surface AgCl electrode. Key Results: Mimosa leaves, pea tendrils, Venus flytraps and sundew traps all lost both their autonomous and touch-induced movements after exposure to anaesthetics. In Venus flytrap, this was shown to be due to the loss of action potentials under diethyl ether anaesthesia. The same concentration of diethyl ether immobilized pea tendrils. Anaesthetics also impeded seed germination and chlorophyll accumulation in cress seedlings. Endocytic vesicle recycling and reactive oxygen species (ROS) balance, as observed in intact Arabidopsis root apex cells, were also affected by all anaesthetics tested. Conclusions: Plants are sensitive to several anaesthetics that have no structural similarities. As in animals and humans, anaesthetics used at appropriate concentrations block action potentials and immobilize organs via effects on action potentials, endocytic vesicle recycling and ROS homeostasis. Plants emerge as ideal model objects to study general questions related to anaesthesia, as well as to serve as a suitable test system for human anaesthesia.

Cold plasma interactions with plants: Morphing and movements of Venus flytrap and Mimosa pudica induced by argon plasma jet.

Low temperature (cold) plasma finds an increasing number of applications in biology, medicine and agriculture. In this paper, we report a new effect of plasma induced morphing and movements of Venus flytrap and Mimosa pudica. We have experimentally observed plasma activation of sensitive plant movements and morphing structures in these plants similar to stimulation of their mechanosensors in vivo. Application of an atmospheric pressure argon plasma jet to the inside or outside of a lobe, midrib, or cilia in Dionaea muscipula Ellis induces trap closing. Treatment of Mimosa pudica by plasma induces movements of pinnules and petioles similar to the effects of mechanical stimulation. We have conducted control experiments and simulations to illustrate that gas flow and UV radiation associated with plasma are not the primary reasons for the observed effects. Reactive oxygen and nitrogen species (RONS) produced by cold plasma in atmospheric air appear to be the primary reason of plasma-induced activation of phytoactuators in plants. Some of these RONS are known to be signaling molecules, which control plants' developmental processes. Understanding these mechanisms could promote plasma-based technology for plant developmental control and future use for plant protection from pathogens. Our work offers new insight into mechanisms which trigger plant morphing and movement.

Modifications of the chemical structure of phenolics differentially affect physiological activities in pulvinar cells of Mimosa pudica L. II. Influence of various molecular properties in relation to membrane transport.

Early prediction of compound absorption by cells is of considerable importance in the building of an integrated scheme describing the impact of a compound on intracellular biological processes. In this scope, we study the structure-activity relationships of several benzoic acid-related phenolics which are involved in many plant biological phenomena (growth, flowering, allelopathy, defense processes). Using the partial least squares (PLS) regression method, the impact of molecular descriptors that have been shown to play an important role concerning the uptake of pharmacologically active compounds by animal cells was analyzed in terms of the modification of membrane potential, variations in proton flux, and inhibition of the osmocontractile reaction of pulvinar cells of Mimosa pudica leaves. The hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA), polar surface area (PSA), halogen ratio (Hal ratio), number of rotatable bonds (FRB), molar volume (MV), molecular weight (MW), and molar refractivity (MR) were considered in addition to two physicochemical properties (logD and the amount of non-dissociated form in relation to pKa). HBD + HBA and PSA predominantly impacted the three biological processes compared to the other descriptors. The coefficient of determination in the quantitative structure-activity relationship (QSAR) models indicated that a major part of the observed seismonasty inhibition and proton flux modification can be explained by the impact of these descriptors, whereas this was not the case for membrane potential variations. These results indicate that the transmembrane transport of the compounds is a predominant component. An increasing number of implicated descriptors as the biological processes become more complex may reflect their impacts on an increasing number of sites in the cell. The determination of the most efficient effectors may lead to a practical use to improve drugs in the control of microbial attacks on plants.

Memory elements in the electrical network of Mimosa pudica L.

The fourth basic circuit element, a memristor, is a resistor with memory that was postulated by Chua in 1971. Here we found that memristors exist in vivo. The electrostimulation of the Mimosa pudica by bipolar sinusoidal or triangle periodic waves induce electrical responses with fingerprints of memristors. Uncouplers carbonylcyanide-3-chlorophenylhydrazone and carbonylcyanide-4-trifluoromethoxy-phenyl hydrazone decrease the amplitude of electrical responses at low and high frequencies of bipolar sinusoidal or triangle periodic electrostimulating waves. Memristive behavior of an electrical network in the Mimosa pudica is linked to the properties of voltage gated ion channels: the channel blocker TEACl reduces the electric response to a conventional resistor. Our results demonstrate that a voltage gated K(+) channel in the excitable tissue of plants has properties of a memristor. The discovery of memristors in plants creates a new direction in the modeling and understanding of electrical phenomena in plants.

Chemical investigation of Cyperus distans L. and inhibitory activity of scabequinone in seed germination and seedling growth bioassays.

Chemical investigation of the rhizomes of Cyperus distans (Cyperaceae) led to the identification of α-ciperone, cyperotundone and scabequinone, besides other common constituents. Complete assignment of the (13)C NMR data of scabequinone is being published for the first time. The inhibitory effects of C. distans extracts and scabequinone on the seed germination and seedling growth of Mimosa pudica, Senna obtusifolia and Pueraria phaseoloides were evaluated. Seed germination inhibition bioassay revealed that S. obtusifolia (52-53%) was more sensitive to the hexane and the methanol extracts at 1% than M. pudica (0-10%). Scabequinone at 250 mg L⁻¹ displayed seed germination inhibitions more than 50% and radicle growth reduction of more than 35% of the test species S. obtusifolia and P. phaseoloides, while the hypocotyl growth of M. pudica was significantly affected (>50%) by the quinone at the same concentration. These results demonstrate that scabequinone contributes to the overall inhibitory activities of C. distans.

Flavonoids from leaves of Derris urucu: assessment of potential effects on seed germination and development of weeds.

In some previous studies, we described the isolation of nine compounds from leaves of Derris urucu, a species found widely in the Amazon rainforest, identified as five stilbenes and four dihydroflavonols. In this work, three of these dihydroflavonols [urucuol A (1), urucuol B (2) and isotirumalin (3)] were evaluated to identify their potential as allelochemicals, and we are also reporting the isolation and structural determination of a new flavonoid [5,3'-dihydroxy-4'-methoxy-(7,6:5″,6″)-2″,2″-dimethylpyranoflavanone (4)]. We investigated the effects of the dihydroflavonols 1-3 on seed germination and radicle and hypocotyl growth of the weed Mimosa pudica, using solutions at 150 mg.L-1. Urucuol B, alone, was the substance with the greatest potential to inhibit seed germination (26%), while isotirumalin showed greater ability to reduce the development of the hypocotyl (25%), but none of the three substances showed the potential to inhibit radicle. When combined in pairs, the substances showed synergism for the development of root and hypocotyl and effects on seed germination that could be attributed to antagonism. When tested separately, the trend has become more intense effects on seed germination, while for the substances tested in pairs, the intensity of the effect was greater on development of weed.

Early membrane events induced by salicylic acid in motor cells of the Mimosa pudica pulvinus.

Salicylic acid (o-hydroxy benzoic acid) (SA) induced a rapid dose-dependent membrane hyperpolarization (within seconds) and a modification of the proton secretion (within minutes) of Mimosa pudica pulvinar cells at concentrations higher than 0.1mM. Observations on plasma membrane vesicles isolated from pulvinar tissues showed that SA acted directly at the membrane level through a protonophore action as suggested by the inhibition of the proton gradient and the lack of effect on H(+)-ATPase catalytic activity. Comparative data obtained with protonophores (carbonylcyanide-m-chlorophenylhydrazone and 2,4-dinitrophenol) and inhibitors of ATPases (vanadate, N,N'-dicyclohexylcarbodiimide, and diethylstilbestrol) corroborated this conclusion. Consequently, the collapse of the proton motive force led to an impairment in membrane functioning. This impairment is illustrated by the inhibition of the ion-driven turgor-mediated seismonastic reaction of the pulvinus following SA treatment. SA acted in a specific manner as its biosynthetic precursor benzoic acid induced much milder effects and the m- and p-OH benzoic acid derivatives did not trigger similar characteristic effects. Therefore, SA may be considered both a membrane signal molecule and a metabolic effector following its uptake in the cells.

Inhibitory effects against pasture weeds in Brazilian Amazonia of natural products from the marine brown alga Dictyota menstrualis.

Fractions of the acetone extract and a mixture of two diterpenes from the marine brown alga Dictyota menstrualis were prepared with the aim of identifying potential effects on the germination of seeds and on elongation of the radicle and hypocotyl of the weeds Mimosa pudica and Senna obtusifolia. The bioassay on seed germination was performed in controlled conditions of 25 degreeC temperature and a 12 hour photoperiod, while the one concerning radicle and hypocotyl elongation was performed at the same temperature, though adopting a photoperiod of 24 hours. The results varied according to the receptor species, the fraction utilized, and its concentration. TLC analysis of the fractions and comparison with isolated products indicated that the diterpenes pachydictyol A and isopachydictyol A were the most abundant compounds in fraction HE, whereas the diterpene 6-hydroxy-dichotomano-2, 13-diene-16, 17-dial (3) was the most abundant compound in fractions DC and EA. Analysis of less polar fractions (in n-hexane, dichloromethane and ethyl acetate) revealed values of less than 30% inhibition. On the other hand, the ethanol/water fraction was the most active in all instances. The biological activity of these fractions must be due to the presence of known diterpenes and/or sulfated polysaccharides isolated in earlier studies.

Mimosa pudica, Dionaea muscipula and anesthetics.

Some studies showed that anesthetics reduce the response of physical stimuli in Mimosa pudica and in Venus Flytrap (Dionaea muscipula), peculiar plants that have the ability to respond to touch stimuli. In this research we tested the effects of ketamine, lidocaine, diethyl ether, and amlodipine on the movements of Mimosa pudica and Venus Flytrap. With a literature review, we tried to bring elements to theorize about the interaction of these substances with these plants. The angular displacement in Mimosa´s petiole and in Dionaea leaves is what was measured to compare the drugs group with control groups.

Lead tolerance and phytoremediation potential of Brazilian leguminous tree species at the seedling stage.

A greenhouse pot experiment was conducted to evaluate the potential of three Brazilian leguminous woody species, Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, for the revegetation of lead- (Pb-) contaminated areas. The response of seedlings to increasing Pb concentrations (0, 250, 500 and 1000 mg kg(-1)) in the soil was studied. In addition to Pb accumulation and translocation, the following parameters were assessed: chlorophyll, nitrate, ammonia, lipid peroxidation (MDA) and free amino acid content; seedling growth; and nitrogenase activity. No differences were observed in the germination of woody species seeds sown in soils with or without Pb addition. M. caesalpiniaefolia did not show visual symptoms of Pb toxicity, while the other two species demonstrated stress symptoms, including reduced shoot biomass yield, leaf area and height. Biochemical analyses of plant tissues revealed markedly different responses to increasing Pb concentrations, such as changes in foliar soluble amino acid composition in S. parahyba; changes in ammonia and nitrate content in E. speciosa, M. caesalpiniaefolia and S. parahyba; and changes in MDA content in S. parahyba. The levels of chlorophyll a and b and carotenoid were affected in the species studied. For the Nitrogen-fixing (N(2)-fixing) species E. speciosa, an increase of Pb in the soil affected nodule formation and growth, which led to reduced nitrogenase activity in seedlings. The concentration of Pb in shoots and roots increased with the Pb concentration in soil. However, most of the Pb absorbed accumulated in the roots, and only a small fraction was translocated to aboveground parts. These findings were confirmed by the low bioconcentration factor (BCF) and translocation factor (TF) values for the three species. The tolerance index (TI) values suggested that M. caesalpiniaefolia, a N(2)-fixing tree, was the species that was most tolerant to high Pb concentrations in soil, while E. speciosa and S. parahyba showed moderate tolerance. Of the three Brazilian native woody species studied, M. caesalpiniaefolia was found to have the highest Pb tolerance and phytostabilisation potential in Pb-contaminated soils.

Early events induced by chitosan on plant cells.

Chitosan (a polymer of beta-1,4-glucosamine residues) is a deacetylated derivative of chitin which presents antifungal properties and acts as a potent elicitor of plant resistance against fungal pathogens. Attention was focused in this study on the chitosan-induced early events in the elicitation chain. Thus, it was shown that chitosan triggered in a dose-dependent manner rapid membrane transient depolarization of Mimosa pudica motor cells and, correlatively, a transient rise of pH in the incubation medium of pulvinar tissues. By using plasma membrane vesicles (PMVs), it was specified that a primary site of action of the compound is the plasma membrane H(+)-ATPase as shown by its inhibitory effect on the proton pumping and the catalytic activity of the enzyme up to 250 microg ml(-1). As a consequence, chitosan treatment modified H(+)-mediated processes, in particular it inhibited the uptake of the H(+)-substrate co-transported sucrose and valine, and inhibited the light-induced H(+)/K(+)-mediated turgor reaction of motor cells. The present data also allowed the limit of the cytotoxicity of the compound to be established close to a concentration of 100 microg ml(-1) at the plasma membrane level. As a consequence, chitosan could be preferably used in plant disease control as a powerful elicitor rather than a direct antifungal agent.

Weed growth inhibitors from Aspergillus fischeri TISTR 3272.

Chloroform and ethyl acetate extracts of Aspergillus fischeri TISTR 3272 showed good growth inhibitory activity on Mimosa pigra and Echinochloa crus-galli. Bioassay-directed fractionation of the active extracts led to the isolation of five known compounds, (+)-terrein (1), (-)-6-hydroxymellein (2), two diketopiperazines (cyclo-(S-Pro-S-Leu) (3) and cyclo-(S-Pro-S-Val) (4)) and butyrolactone I (5). Compounds 2-5 were reported for the first time in this fungus. Their structural determinations were based on analyses of spectroscopic data and their weed growth inhibitory effects were assessed.

Chemical basis of plant leaf movement.

Nyctinastic plants open and close leaves with a circadian rhythm. Here we discuss chemical aspects of the mechanism of nyctinastic leaf movement. Nyctinastic plants from five different genera are known to contain species-specific leaf-opening and leaf-closing factors. The relative concentrations of leaf-closing and leaf-opening factors of the nyctinastic plant Phyllanthus urinaria change circadianly, suggesting that nyctinastic movement is regulated by two classes of circadianly regulated factors with opposing functions. A closing and an opening factor of Albizzia, when linked to a fluorescent dye, both specifically labeled motor cells of pluvini. A membrane fraction of pluvini contains proteins of 210 and 180 kDa that bind to a leaf-opening factor of Cassia mimosoides. The molecular identification of these proteins is underway.

Membrane effects of 2,4-dichlorophenoxyacetic acid in motor cells of Mimosa pudica L.

2,4-dichlorophenoxyacetic acid applied to excised leaves of Mimosa pudica L. inhibited in a dose-dependent manner the shock-induced pulvinar movement. This inhibition was negatively correlated with the amount of [(14)C] 2,4-dichlorophenoxyacetic acid present in the vicinity of the motor cells. Although 2,4-dichlorophenoxyacetic acid is a weak acid, its greatest physiological efficiency was obtained with pH values close to neutrality. This observation opens the question of its mode of action which may be through external signaling or following internal transport by a specific anionic form transporter. The effect was related to molecular structure since 2,4-dichlorophenoxyacetic acid>3,4-dichlorophenoxyacetic acid>2,3-dichlorophenoxyacetic acid. An essential target of 2,4-dichlorophenoxyacetic acid action lies at the plasmalemma as indicated by the induced hyperpolarization of the cell membrane. Compared to indole-3-acetic acid and fusicoccin, it induced a complex effect on H(+) fluxes. Applied to plasma membrane vesicles purified from motor organs, 2,4-dichlorophenoxyacetic acid enhanced proton pumping, but, unlike fusicoccin, it did not increase the H(+)-ATPase catalytic activity in our experimental conditions. Taken together, the data suggest that 2,4-dichlorophenoxyacetic acid acts on cell turgor variation and the concomittant ion migration, in particular K(+), by a mechanism involving specific steps compared to indole-3-acetic acid and fusicoccin.

Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species.

Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for P. nigra, V. lantana, and F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury.

Specific perception of ergosterol by plant cells.

Ergosterol (a fungal membrane component) induced modification of proton fluxes and membrane hyperpolarization in motor cells of Mimosa pudica. These reactions appear specific since they were not induced by the other sterols tested. A specific desensitization was observed, since cells did not react to a second ergosterol application. Exposed at first to other sterols, cells remained reactive to ergosterol. Comparatively, chitosan (a fungal wall component with known elicitor properties) triggered a membrane depolarization and also induced specific desensitization. This comparative study shows that ergosterol and chitosan are distinctly perceived by plant cells and induced different early events at the plasma membrane level.