A Revised Method of Condensed Tannin Analysis in Leucaena spp.

The proanthocyanidin (butanol-HCl) assay was used to measure condensed tannin (CT) in extracts from Leucaena spp. at the University of Queensland. Inconsistent results were found to be caused by the iron catalyst in the butanol/HCl reagent and the presence of ascorbic acid in the sample matrix which enhanced anthocyanidin development. In addition, preparation of sample extracts by back extraction with organic solvents reduced CT recoveries. An accurate and rapid technique was developed that measures CT directly in 70% aqueous acetone 0.1% (w/v) sodium metabisulphite plant extracts

Adapting agricultural water use to climate change in a post-Soviet context: challenges and opportunities in southeast Kazakhstan

The convergence of climate change and post-Soviet socio-economic and institutional transformations has been underexplored so far, as have the consequences of such convergence on crop agriculture in Central Asia. This paper provides a place-based analysis of constraints and opportunities for adaptation to climate change, with a specific focus on water use, in two districts in southeast Kazakhstan. Data were collected by 2 multi-stakeholder participatory workshops, 21 semi-structured in-depth interviews, and secondary statistical data. The present-day agricultural system is characterised by enduring Soviet-era management structures, but without state inputs that previously sustained agricultural productivity. Low margins of profitability on many privatised farms mean that attempts to implement integrated water management have produced water users associations unable to maintain and upgrade a deteriorating irrigation infrastructure. Although actors engage in tactical adaptation measures, necessary structural adaptation of the irrigation system remains difficult without significant public or private investments. Market-based water management models have been translated ambiguously to this region, which fails to encourage efficient water use and hinders adaptation to water stress. In addition, a mutual interdependence of informal networks and formal institutions characterises both state governance and everyday life in Kazakhstan. Such interdependence simultaneously facilitates operational and tactical adaptation, but hinders structural adaptation, as informal networks exist as a parallel system that achieves substantive outcomes while perpetuating the inertia and incapacity of the state bureaucracy. This article has relevance for critical understanding of integrated water management in practice and adaptation to climate change in post-Soviet institutional settings more broadly

Rhizotoxicity of aluminate and polycationic aluminium at high pH

Although monomeric Al species are often toxic in acidic soils, the effects of the aluminate ion (Al(OH)4-) on roots grown in alkaline media are still unclear. Dilute, alkaline (pH 9.5) nutrient solutions were used to investigate the effects of Al(OH)4- on root growth of mungbean (Vigna radiata L.). Root growth was reduced by 13 % after 3 d growth in solutions with an Al(OH)4- activity of 16 μM and no detectable polycationic Al (Al13). This decrease in root growth was associated with the formation of lesions on the root tips (due to the rupturing of the epidermal and outer cortical cells) and a slight limitation to root hair growth (particularly on the lateral roots). When roots displaying these symptoms were transferred to fresh Al(OH)4- solutions for a further 12 h, no root tip lesions were observed and root hair growth on the lateral roots improved. The symptoms were similar to those induced by Al13 at concentrations as low as 0.50 μM Al which are below the detection limit of the ferron method. Thus, Al(OH)4- is considered to be non-toxic, with the observed reduction in root growth in solutions containing Al(OH)4- due to the gradual formation of toxic Al13 in the bulk nutrient solution resulting from the acidification of the alkaline nutrient solution by the plant roots

Evaluation of Cu-ethylenediamine metal ion buffers as calibrants for ion-selective electrode measurement of copper in fresh water systems

An investigation was made into the accuracy of cupric ion selective electrode (ISE) measurement of Cu in solutions approximating acidic freshwaters with Cu-ethylenediamine buffers used as the calibrants. This method overestimates the free Cu compared with calibration using Cu(NO ) standards, the standard addition method, and speciation modelling calculations. Statistical tests showed a small, but significant, difference between the intercepts of the linear Nernstian regressions of the calibration plots of Cu-en buffer standardisation and direct calibration with Cu(NO ) standards in matrix that matches the samples. The difference in the intercepts, which corresponds with E values of the electrode, is not well understood, but is possibly caused by potentially interfering cations such as Fe2+. The results of this study showed that down to 10 M Cu , where a linear Nernstian response is possible, the Cu ISE is probably better calibrated using Cu standards prepared in the same matrix as the sample solutions to avoid potential matrix effects

Characterisation of fulvic and humic acids from leaves of Eucalyptus camaldulensis and from decomposed hay

Soluble soil organic components including fulvic acid (FA) and humic acid (HA) have the ability to complex cations, such as plant toxic monomeric aluminium (Al). We describe the chemistry of FA and HA extracted from two sources before their use in solution culture experiments aimed at determining their ability to ameliorate Al toxicity. Aqueous extracts containing FA and HA were obtained from aerobically incubated leaves of Eucalyptus camaldulensis (Eucalyptus) and decomposed grass and lucerne hay (Compost). The FA and HA were separated and concentrated by precipitation and ion adsorption using XAD-7 resin, purified and dried. Selected elemental properties, size exclusion chromatograms and solid state 13C-NMR spectra obtained for the FA and HA from both sources showed distinct structural differences. The FA obtained from the extensively decomposed Compost consisted of simpler and smaller components. The younger FA and HA obtained from the freshly prepared extract of Eucalyptus were very similar in their chemical attributes

Aluminium reactions with polygalacturonate and related organic ligands

Aluminium (Al), in inorganic monomeric forms, has been recognised as a limiting factor for root growth in many acid soils. Plant tolerance to Al may be achieved by the detoxification (complexation) of Al by organic ligands present in the rhizosphere. The Al-complexing ability of seven organic ligands, citric, oxalic, gluconic, glucuronic, mucic, galacturonic and polygalacturonic (pectin) acids, was investigated. The proportion of organically-complexed Al was determined using colorimetric methods based on differences in reaction rate with pyrocatechol violet or aluminon. The colorimetric methods confirmed that citric acid forms a strong complex with Al at pH 4.2. In contrast, pectin and related organic ligands weakly complexed Al in acidic conditions. In an additional study, the Al-binding ability of pectin and Ca-pectate was compared at a biologically significant concentration of 32 μM Al. Only 29% of free Al remained in solution in the presence of Ca-pectate, while 54% remained when pectin was present. This suggests that Ca-pectate, rather than pectin, is responsible for binding Al in root cell walls and consequently plays an important role in Al toxicity to plants. Root growth of mungbean (Vigna radiata (L.) Wilczek) confirmed differences in the ability of citrate, oxalate and galacturonate to complex Al

Reactions between aluminum and sulfate in dilute nutrient solutions with varying degrees of hydrolysis

Effects of hydrolysis of Al (300 μM) at OH/Al molar ratios of 0, 1, or 2 on forms of Al were studied in de-ionized water and in a dilute nutrient solution matrix during 20 d of aging. In the dilute nutrient solution series, varying sulfate (SO) additions were made to attain a SO/Al molar ratio of 5 or 20. Aluminum was supplied as AlK(SO)•12HO or Al(NO)•9HO, and additional SO was supplied as CaSO•2HO. The solution pH varied from 4.2 to 4.7 with increase in degree of hydrolysis. The trends in pH with time were generally similar in the absence or presence of basal nutrients. In the absence of basal nutrients, increase in OH/Al molar ratio decreased the concentration of total Al in solution with AlK(SO) but not with Al(NO). However, in the presence of basal nutrients, concentrations of total and monomeric Al decreased with an increase in OH/Al molar ratio in solutions with either AlK(SO) or Al(NO). Increase in the SO/Al ratio resulted in a slight but consistent decrease in concentrations of monomeric and total Al only in hydrolyzed Al solutions. Precipitates found in hydrolyzed Al solutions were amorphous and contained Al and S, with the S/Al ratio ranging from 0.15 to 0.27, depending on the source of Al, the degree of hydrolysis, the presence of basal nutrients, and the SO/Al molar ratio. Speciation calculations using the MINTEQ program showed super-saturation with respect to AlOHSO, Al(OH)SO, and alunite in solutions containing a SO/Al molar ratio of 5 or 20 using either AlK(SO) or Al(NO) and in solutions containing AlK(SO) with no addition of SO

Soil carbon determination by high temperature combustion - A comparison with dichromate oxidation procedures and the influence of charcoal and carbonate carbon on the measured value

The measurement of organic carbon in soils has traditionally used dichromate oxidation procedures including the Wakley and Black and the Heanes methods. The measurement of carbon in soils by high temperature combustion is now widely used providing a rapid automated procedure without the use of toxic chemicals. This procedure however measures total carbon thus requiring some means of correction for soil samples containing carbonate and charcoal forms of carbon. This paper examines the effects of known additions of charcoal to a range of soil types on the results obtained by the Walkley and Black, Heanes and combustion methods. The results show, that while the charcoal carbon does not react under Walkley and Black conditions, some proportion does so with the Heanes method. A comparison of six Australian Soil and Plant Analysis Council reference soil samples by the three methods showed good agreement between the Heanes method, the combustion method and only slightly lower recoveries by the Walkley and Black procedure. Carbonate carbon will cause an overestimation of soil organic carbon by the combustion method thus requiring a separate determination of carbonate carbon to be applied as a correction. This work shows that a suitable acid pre-treatment of alkaline soils in the sample boats followed by a drying step eliminates the carbonate carbon prior to combustion and the need for an additional measurement. The measurement of carbon in soils by high temperature combustion in an oxygen atmosphere has been shown to be a rapid and reliable method capable of producing results in good agreement with one of the established dichromate oxidation procedures

Determination of dissolved organic carbon by inductively coupled plasma atomic emission spectrometry

Dissolved organic carbon (DOC) present in soil solutions was measured by inductively coupled plasma atomic emission spectrometry (ICPAES) using the two C(I) lines at 193.09 nm and 247.856 nm. Carbon standards, prepared from sucrose in the range 100 to 1,000 mg/L, produced linear coefficients of determination of r≥ 0.9998 for each of the lines with calculated detection limits of 0.034 and 1.094 mg/L for each line, respectively. Inorganic carbon was eliminated from solution by the addition of concentrated nitric acid and sparging with high purity nitrogen for 30 min. A comparison of the DOC values for soil solutions extracted from nine soil samples by ICPAES and dichromate oxidation showed a high degree of correlation (r≥ 0.9982)