Tropic Acid Research Articles

Flexibility of nitrogen metabolism in the tropical C3crassulacean acid metabolism tree species Clusia minor.

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. The C3-crassulacean acid metabolism tropical hemiepiphytic tree, Clusia minor L., is highly flexible in terms of ecological sites occupied, life forms, and photosynthetic and metabolic pathways. We studied nitrogen uptake patterns in two glasshouse 15N-labelling experiments using hydroponically-grown plants and excised roots of pot-grown C. minor, and investigated leaf and root nitrate reductase activity (NRA) in a field study in Venezuela. The results of both 15N-uptake experiments indicate that C. minor utilized all offered nitrogen sources, but clearly preferred to take up NH4+ over glycine (GLY) and NO3-. The uptake pattern of NH4+ and NO3- was identical in intact plants and excised roots, and NH4+ was taken up to a much larger extent in both experiments. Gas chromatography-mass spectrometry (GC-MS) analysis of amino acids in excised roots revealed that glutamine (45 atom-%), glutamate (23 atom-%) and alanine (34 atom-%) accounted for most of the labelled soluble amino acids after 2-h labelling with 15NH4+. High amounts of 15N in GLY and serine confirmed that GLY was taken up as an intact molecule and metabolized in the excised roots. With 15NO3- labelling, only a small amount of 15N was found in the amino acid fraction, indicating a low NO3- assimilation rate by nitrate reductase. This was confirmed by low NRA of leaves and roots in C. minor plants in Venezuela. It appears, therefore, that a high degree of plasticity is not reflected in nitrogen uptake and metabolism. Although C. minor exhibits clear preferences for NH4+ uptake, it can utilize other sources of nitrogen, and the nitrogen uptake pattern represents an adaptation to the natural environments in which C. minor can grow.

Phosphorus fertility recapitalization of nutrient-depleted tropical acid soils with reactive phosphate rock: An assessment using the isotopic exchange technique

A “soil P fertility recapitalization” initiative utilizinglarge rates of phosphate rocks (PRs) was proposed to improve the soil P statusand increase the sustainable food production in acid and P-deficient tropicalsoils. Two series of experiments were carried out using five tropical acidsoilstreated with heavy applications of Gafsa phosphate rock (GPR). In the firstseries, the soils were mixed with GPR at the following application rates: 0,500, 1000 and 2000 mg P·kg−1, andincubatedfor one month in moist conditions. In another series, 1000 mg Pkg−1 applied as GPR was added to three soils andincubated for 1.5 month; thereafter 50 mg P kg−1as triple superphosphate (TSP) were added. The 32P isotopic exchangemethod was utilized to assess the contribution of GPR to the available soil P.Changes in amounts, E, of P transferred with time as phosphate ions from thesoil particles to the soil solution as well as changes in pH, calcium andphosphate concentrations in soil suspensions were determined. It was foundthat:(i) the contribution of P from GPR to recapitalization of soil P fertility wasmainly assessed by E pool size, pH, calcium and phosphate concentrations; othervariables were not significant at the 0.1 level; (ii) heavy applications of GPRdid not saturate all the P sorption sites, P freshly applied as water-soluble Pwas still sorbed; (iii) recapitalization of soil P fertility using GPR waspartly obtained in some acid tropical soils; (iv) Upon dissolution, GPRprovidedcalcium ions to crops and to soils, thus reducing Al toxicity, but its limingeffect was limited. To explain these effects with heavy application rates ofGPR, it was postulated that a coating of Al and Fe compounds is formed aroundPRparticles with time, thus reducing further dissolution.

Comparison of greenhouse and 32 P isotopic laboratory methods for evaluating the agronomic effectiveness of natural and modified rock phosphates in some acid soils of Ghana

Phosphorus deficiency is one of the major constraints for normal plant growth and crop yields in the acid soils of Ghana and therefore addition of P inputs is required for sustainable crop production. This is often difficult, if not impossible for small-scale farmers due to the high cost of mineral P fertilizers and limited access to fertilizer supplies. Direct application of finely ground phosphate rocks (PRs) and their modified forms have been recommended as alternatives for P fertilization. The direct application of the natural and modified PRs to these acid soils implies the need to predict their agronomic effectiveness of the PRs in the simplest and most cost-effective manner. In this study the classical greenhouse pot experiment was compared to the 32P isotopic kinetics laboratory method for evaluating the agronomic effectiveness of natural and modified Togo PR in six highly weathered Oxisols from southwest Ghana. In the 32P isotopic kinetics laboratory experiment the six soil samples were each fertilised at the rate of 50 mg P kg−1 soil in the form of triple superphosphate (TSP), Togo PAPR-50%, and Togo PR, respectively. Controls without P amendment were also included. Isotopic exchange kinetics experiments were carried out on two sets of samples, immediately after P fertilizer additions (without incubation) and after 6 weeks of incubation under wet conditions and at a room temperature of 25 °C. In the greenhouse pot experiment, P fertilizers in the form of Togo PR, Togo PAPR, Mali PR and TSP were each applied to the six soils at rates equivalent to 0, 30, 60, and 120 kg P ha−1, respectively. The P fertilizers were mixed with the soils and maize (Zea mays L.) variety Obatanpa was grown for 42 days before harvest. The isotopic kinetics data of the control samples indicated that 5 of the studied soils had very low P fertility status as reflected by their low P concentrations in solution (CP PAPR = Mali PR >Togo PR = Control. Both the laboratory index, Pdff% in soil solution derived from the isotopic method and the RCRI values obtained from the pot experiment produced similar results in ranking the P fertilizers tested according to their agronomic effectiveness. The isotopic kinetic method may be considered as an alternative to both greenhouse and field methods in the evaluation of agronomic effectiveness of P fertilizers in tropical acid soils when it offers comparative advantages in assessing the soil P status and its changes. But trained staff and adequate laboratory facilities are needed to perform this technique. Also the method can be used as a reference for comparison purposes as in this case. Further research is needed to assess the overall agronomic effectiveness (immediate and residual effects) of PR sources in predominant cropping systems of this region of Ghana.

Correspondence analysis evaluation of linear nutrient distribution in root tips of the tropical forage Brachiaria brizantha

The technique of correspondence analysis was applied to a set of data obtained from X-ray elemental analysis by nuclear microscopy. Hydroponic experiments simulating tropical acid soil conditions were carried out to determine possible mechanisms of Al-toxicity stress on specific varieties of the genus Brachiaria. In particular the species Brachiaria brizantha was tested for gradient variation along the central cylinder of selected root tips. Single-point irradiations by nuclear microscopy gave some indication of a possible trace element profile gradient along the root axis. To be able to extrapolate the possible correlation and trace elemental concentrations gradients to a more confident level, this nuclear microscopy data obtained was analysed by correspondence analysis. A clear gradient on the plot of the first two axes of the correspondence analysis was found. The correlation of Ca and Cu as well as that of K and Cl were established.

Availability and plant uptake of nutrients following the application of paper pulp and lime to tropical acid soils

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IMPROVING NUTRIENT USE EFFICIENCY OF ANNUAL CROPS IN BRAZILIAN ACID SOILS FOR SUSTAINABLE CROP PRODUCTION

In tropical acid soils, acidity is an important constraint for availability and uptake of nutrients by annual crops, and this leads to lower crop yields. Factors that contribute to low nutrient uptake efficiencies in these soils are low natural levels of most essential plant nutrients and unfavorable soil and plant environments. High P fixation capacity, Al, Mn and H toxicity, low activities of bene-ficial microorganisms, soil compaction, infestation of weeds, diseases and insects, drought and intensive monoculture are some of the major factors that contribute to the unfavorable soil and plant environments. Improving nutrient use efficiency in these soils demand adoption of special management practices. These practices include timely application of adequate levels of lime, gypsum and fertilizers to meet crop demand, use of proper crop rotation, improvement of organic matter content, control of soil erosion and use of acid tolerant crop species and cultivars within species.

Characteristics of wood ash and influence on soil properties and nutrient uptake: an overview

Wood industries and power plants generate enormous quantities of wood ash. Disposal in landfills has been for long a common method for removal. New regulations for conserving the environment have raised the costs of landfill disposal and added to the difficulties for acquiring new sites for disposal. Over a few decades a number of studies have been carried out on the utilization of wood ashes in agriculture and forestry as an alternative method for disposal. Because of their properties and their influence on soil chemistry the utilization of wood ashes is particularly suited for the fertility management of tropical acid soils and forest soils. This review principally focuses on ash from the wood industry and power plants and considers its physical, chemical and mineralogical characteristics, its effect on soil properties, on the availability of nutrient elements and on the growth and chemical composition of crops and trees, as well as its impact on the environment.

Formation of gibbsite in the presence of 2:1 minerals: an example from Ultisols of northeast India

AbstractThere are two different views regarding the genesis of gibbsite in tropical acid soils: (1) direct weathering of primary Al-silicate minerals; and (2) transformation through clay mineral intermediates. We investigated the genesis of gibbsite in two representative Ultisols from northeastern India. Gibbsite in these Ultisols appears to be the remnant of earlier weathering products of aluminosilicate minerals formed in a neutral to alkaline pedochemical environment. The mere presence of gibbsite in these soils, therefore, does not indicate their advanced stage of weathering. The formation of typically rod-shaped and well-crystallized gibbsite in both the coarse and fine soil fractions in the presence of large amounts of 2:1 minerals indicates that the anti-gibbsite hypothesis may not be tenable in these tropical acid soils. A schematic model for the formation of gibbsite and kaolin in Ultisols is proposed.

Bioactivation of Poorly Soluble Phosphate Rocks with a Phosphorus‐Solubilizing Fungus

Many studies have demonstrated ineffectiveness of finely ground phosphate rock (PR) use due to the low solubility of its P contents. This study was conducted to develop a simple, effective, and environmentally sound process to improve P availability of PR to crops by using a phosphate‐solubilizing fungus (PSF), Aspergillus niger BCC F.194, isolated from tropical acid soils. The optimum incubation period and the optimum level of PR were determined. The P‐solubilizing effect of the supernatant of 9‐d‐old liquid culture supernatant (LCS) of the fungus was also determined by reacting it at various concentrations with Morrocan phosphate rock (MPR). The inoculation of the growth media with the PSF A. niger resulted in the highest P solubility of the rock after 9 d of culturing at 2.5 g L−1 MPR. Up to a certain degree, direct inoculation of fungal biomass and its LCS onto MPR caused a remarkable increase in 2% citric acid–soluble P, but not in water‐soluble P content. The possibilities of using the LCS instead of H2SO4 in superphosphate (SP) production and using both with lower H3PO4 concentrations were investigated with MPR as raw materials. Replacement of H2SO4 by the LCS in the SP production process yielded a comparable 2% citric acid–soluble P content. Combining the LCS and H2SO4 reduced the consumption of H3PO4 that occurs in standard SP production. This LCS technique provides a practical means for an effective bioactivation of PR intended for both as a P fertilizer and a raw material of the SP.

Chirality of natural products: hyoscyamine and scopolamine

Monthly changes of the content-ratio between S-(-)- and R-(+)-hyoscyamine as well as those between S-(-)- and R-(+)-scopolamine in the leaves of Datura metel L. cultivated in the field, were quantitatively analyzed by the use of HPLC with a chiral adsorbent. It was found that S-(-)-isomer was predominant for hyoscyamine and the ratio of R-(+)-isomer gradually increased during the growth, whereas in the case of scopolamine, S-(-)-isomer was the sole one found throughout the cultivation period. The 1H-NMR study in the CD3OD solution has suggested that S-(-)-hyoscyamine (1) and S-(-)-scopolamine (2) take a "face-to-face" conformation between their tropane skeletons and the benzene rings of the tropic acid moieties. In the presence of an equimolar NaOD in the CD3OD solution, the racemization at C-2' of 1 and 2 proceeded more rapidly than the hydrolysis at the tropic acid ester bond, presumably due to the steric hindrance caused by their "face-to-face" conformations. In the D2O and H2O solutions, on the other hand, the racemization and the hydrolysis of 1 proceeded smoothly, while those of 2 did not occur. It has been supposed that these individual reaction manners are ascribable in considerable extent to the different basicity of N atom in each tropane skeleton of 1 and 2 and to stronger intramolecular hydrogen bond occurring between the carbonyl oxygen at C-1' and the hydroxyl group at C-3' in the tropic acid moiety of 1.

Influence of the ionic strength of nutrient solutions and tropical acid soil solutions on aluminum activity

Aluminum (Al) activity was determined in nutrient solutions and in acid soil solutions. Aluminum concentrations in the solutions ranged from 7.4 μM to 370.3 μM giving values of ionic strength of nutrient solutions higher than the values of acid soil solutions. The increase of ionic strength values was due to the increase of Al concentrations. The values of Al activities of 20 uM in the acid soil solutions were noticed when Al concentrations were lower than 70 μM. On the other hand, these values of Al activities in nutrient solutions were noticed only when the Al concentrations were higher than 70 μM. This study demonstrates why it is important to use higher Al concentrations in nutrient solutions to obtain Al toxic effects.

Dynamics of nutrients in tropical acid soils amended with paper pulp sludge

Paper mill sludge is characterized by high concentrations of organic matter and lime and very low concentrations of heavy metals and organic chemicals. Interest in the recycling of paper mill residuals in developing countries is vital because the use of lime and fertilisers by small farmers is financially prohibitive. The effects of paper pulp sludge and lime on the dynamics of soil nutrients was studied in the laboratory using columns of mixed samples of top soil from three tropical acid soils (Kandiudult). The soil columns were leached over a period of 90 days with de-ionized water in amounts equivalent to the annual rainfall of the sampling site. To assess the amount of nutrient that may become available to plants, NH4OAc-EDTA pH 4.65 soil extractant was used. For all soils, application of paper pulp sludge or lime to tropical acid soils generally resulted in an initial flush and increased concentrations of Ca, Mg, SO4, dissolved organic carbon (DOC) and inorganic carbon in soil leachates. Compared with liming, application of paper pulp sludge reduced NO3 leaching. The amount of leached Ca, DOC and inorganic carbon (mainly HCO3-) increased substantially with the addition of paper pulp sludge or lime. In relation to nutrients, the most meaningful amendment effect that persisted after leaching was a substantially increased available Ca in the treated soil. In addition to increasing Ca levels, the addition of paper pulp sludge increased the concentrations of leached and available Ca. To sustain yield increase with paper pulp sludge, calculation of the optimum quantity to be returned to the soil should be based on losses of Ca by leaching and by plant uptake.

Dynamics of nutrients in tropical acid soils amended with paper pulp sludge

Paper mill sludge is characterized by high concentrations of organic matter and lime and very low concentrations of heavy metals and organic chemicals. Interest in the recycling of paper mill residuals in developing countries is vital because the use of lime and fertilisers by small farmers is financially prohibitive. The effects of paper pulp sludge and lime on the dynamics of soil nutrients was studied in the laboratory using columns of mixed samples of top soil from three tropical acid soils (Kandiudult). The soil columns were leached over a period of 90 days with de-ionized water in amounts equivalent to the annual rainfall of the sampling site. To assess the amount of nutrient that may become available to plants, NH4OAc-EDTA pH 4.65 soil extractant was used. For all soils, application of paper pulp sludge or lime to tropical acid soils generally resulted in an initial flush and increased concentrations of Ca, Mg, SO 4, dissolved organic carbon (DOC) and inorganic carbon in soil leachates. Compared with liming, application of paper pulp sludge reduced NO3 leaching. The amount of leached Ca, DOC and inorganic carbon (mainly HCO 3-) increased substantially with the addition of paper pulp sludge or lime. In relation to nutrients, the most meaningful amendment effect that persisted after leaching was a substantially increased available Ca in the treated soil. In addition to increasing Ca levels, the addition of paper pulp sludge increased the concentrations of leached and available Ca. To sustain yield increase with paper pulp sludge, calculation of the optimum quantity to be returned to the soil should be based on losses of Ca by leaching and by plant uptake.

Chromatographic resolution of organic acids using the Kromasil-CHI-TBB chiral stationary phase

Derivatives of racemic mandelic and tropic acids have been separated directly on a t-butylbenzoylated tartaric acid-based chiral stationary phase (CSP) (Kromasil-CHI-TBB) on both analytical and preparative scales. The resolution of the enantiomers of the model compound, rac-3-methoxytropic acid, was optimized by changing the nature and the composition of the mobile phase. The dominating interaction between the CSP and these hydroxy acids was found to be hydrogen-bonding. Consequently, retention of the analytes on the CSP decreased with increasing polarity of the mobile phase modifier. The separation of the enantiomers was strongly influenced by the π-donating and π-accepting ability of the aryl moiety, and strong electron-withdrawing substituents in the aryl group e.g.,—CF3 result in a loss of chiral recognition. However, the CSP can discriminate between the two enantiomers only when both the aryl moiety and the carboxylic function are directly bonded to the asymmetric carbon atom. The Kromasil-CHI-TBB column displays broad selectivity for the enantiomers of mandelic and tropic acid derivatives, which are relatively simple structures and not easily resolved. Even though the α-values are moderate, the high efficiency of the column facilitates the use of the CSP for the preparative scale chiral separation of a number of these compounds. Chirality 11:420–425, 1999. © 1999 Wiley-Liss, Inc.

Computational and Experimental Examination of the Effect of Inorganic Salts on Chymotryptic Enantioselectivity in Water

Enantioselectivity (E) of α-chymotrypsin in the hydrolysis of tropic (3-hydroxy-2-phenylpro-pionic) acid methyl ester in water was found to be 31 in favor of the R enantiomer. Addition of 1.5 M ammonium or sodium sulfate resulted in a nearly 3-fold drop in the E value. In contrast, thermodynamic calculations predict a 30-40% increase in E. Importantly, these calculations are based on the assumption that the solvent-dependent differences in the desolvation energetics of substrate enantiomers upon formation of their enzyme-bound transition states is the dominant factor by which the solvent affects enzymatic enantioselectivity. Therefore this assumption, validated previously for enzymatic transesterifications in organic solvents and herein for enzymatic hydrolysis in water, does not apply to concentrated aqueous salt solutions. It is hypothesized instead that the sulfate salts may alter the conformation of chymotrypsin. However, the fluorescence and UV absorbance spectra of the enzyme in water and in 1.5 M aqueous salt solutions failed to reveal such changes, suggesting that they must be quite subtle.

OPTIMIZED AND VALIDATED HPLC METHODS FOR COMPENDIAL QUALITY ASSESSMENT. IV. NON-CHIRAL AND CHIRAL PURITY TESTS FOR SOLANACEOUS (TROPANE) ALKALOIDS

The main alkaloids of certain plants of the Solanacea family, such as atropine and scopolamine, together with the synthetic homatropine and methylhomatropine, are routinely used medicinal agents and have their monographs in the modern pharmacopeias. In these monographs, non selective chemical reactions and/or TLC serve for the detection of “foreign alkaloids, related substances, etc.” impurities. In the present paper selective HPLC methods for the compendial purity control of these alkaloids are published. The methods allow the detection of 0.05 μg (= 0.1 %) and the quantitation of 0.05 - 5.0 μg of tropic acid or mandelic acid as hydrolytic degradation product impurities (chromatographic system : C18/methanol - phosphate buffer pH 5 - 5.5). The limit of detection is 0.025 μg. Also, HPLC for the separation of tropane alkaloid enantiomers (chromatographic system : Chiralcel OD/n-hexane - isopropanol - methanol - triethylamine) is presented. Procedure for the enantiomeric purity control of S - (−) - hyoscyamine, the detection of R - (+) - distomer is suggested.

Availability of Nutrients in Wood Ash Amended Tropical Acid Soils

A greenhouse study was conducted to assess nutrient availability in wood ash when applied to surface soil samples of three tropical acid soils (Kandiudult) from Cameroon. Amendments were applied at rates to attain target pH values of 5.5, 6.0 and 6.5. Lime treatments were included as a control. Rye grass (Lolium perenne L.) was grown as an indicator plant for three successive cycles of 40 days each. Data on total harvested dry matter, nutrient uptake, nutrient additions and extractable soil nutrients from treated soils have been used for availability investigations. Application of wood ash resulted in neutralisation of soil acidity, increased exchangeable nutrient bases and decreased extractable micronutrients. Wood ash was in general more effective than lime in increasing dry matter production, mainly because of higher P and K uptake. Phosphorus, Ca, Mg, K, Mn, Zn and Cu from wood ash were used by plants. Wood ash application increased the availability of P, Ca, Mg and K and decreased that of Mn and Zn for plant uptake. Both nutrient additions and nutrient extractions from treated soils provided a reliable measure for plant available nutrients. Soil pH and ECEC affected the availability of P, Ca, Mg and K positively and that of Mn and Zn negatively. Field studies, conducted on a larger number of tropical acid soils, are required to establish prediction models.

Effects of different calcium and sulfate concentrations in nutrient solutions on ionic strength values, aluminum activity, and root growth of maize plants

The effects of increase of the ionic strength by addition of calcium (Ca2+) and sulfate (SO4 2‐) on the activity of monomer aluminum (Al3+) specie and its toxicity on the root growth of maize plants were studied in nutrient solution. The concentration of elements of the nutrients solutions were made from the analysis of the tropical acid soils solutions. Plants of maize were cultivated for seven days in controlled conditions. The ionic strength values of soil solutions were lower than 4,000 μM. The increase of Ca2+ and SO4 2‐ concentrations in nutrient solution resulted in a increase of Ca2+ and SO4 2‐ activities and ionic strength values. With the increase of Ca2+ and SO4 2‐ activities, there was a reduction of Al3+ activities and thus the root growth was increased. The root growth of maize was better correlated with the Al3+ activity values than with Al3+ concentrations.

The separation of ipratropium bromide and its related compounds

Ipratropium bromide, the active component in ipratropium bromide metered dose inhalers (MDI), is used as a bronchodilator for the maintenance and treatment of bronchospasms associated with chronic obstructive pulmonary disease (COPD). The separation of ipratropium bromide, tropic acid, N-isopropyl-nor-atropine (NINA), 8-s ipratropium bromide, apo-ipratropium bromide and the excipients found in the formulation is important for analyzing raw materials and stability samples. We now report a reversed-phase HPLC method that can be used for separating ipratropium bromide and its related compounds, using an acetonitrile/potassium phosphate buffer (100 mM, pH 4.0) gradient mobile phase. Previous methods used for separating ipratropium bromide from its related compounds involved reversed-phase ion-pairing HPLC with UV detection. These methods exhibited less reproducibility, less ruggedness and required a high flow rate. The reported method is linear from 10 to 1000 μg ml −1 with a limit of detection of 60 ng ml −1. In addition, analysis of samples subjected to accelerated stability conditions showed that all degradants are resolved from the active component, resulting in a stability-indicating assay. This assay also saved mobile phase and eliminated problems associated with ion-pairing reagents.

Paper pulp as an amendment to a tropical acid soil: Effects on growth of rye grass

Paper pulp was evaluated, with reference to lime, as a soil amendment to a tropical acid soil (typic Kandiudult). Rye grass (Lolium perenne L.) was grown under greenhouse conditions. Amendments were applied at rates to attain target pH values of 5.5,6.0, and 6.5. Paper pulp and lime were equally effective in increasing dry matter production. Similar to lime, paper pulp provided high calcium (Ca) inputs and alleviated aluminum (Al) and manganese (Mn) toxicity. Paper pulp can be applied to a tropical acid soil as a lime substitute.