Role of root cation‐exchange capacity in differential aluminum tolerance of lotus species

Three experiments were conducted in which roots of two species of Lotus were immersed for up to 40 min in complete nutrient solutions containing 6, 15 or 25 μM Al. The two species tested were L. pedunculatus cv. Grasslands Maku (Al‐tolerant) and L. corniculatus cv. Maitland (Al‐sensitive). There was an initial rapid (< 5 min) decrease in solution Al at 25 μM Al. The effect was less marked with solution Al ≤ 15 μM. The decrease in solution Al was greater in the Al‐sensitive Maitland than in the Al‐tolerant Grasslands Maku, particularly when expressed on the basis of root fresh mass and root length. Root cation‐exchange capacity (CEC) was lower in Grasslands Maku than in Maitland, viz. 23.9 vs 36.5 mmol kg^‐1 dry mass. Maitland roots removed more Al from solution than did those of Maku on the basis of total exchange capacity.

We propose a mechanism of Al tolerance on the basis of the results of this study and of other published information, viz. that differential Al tolerance results from differences in root CEC. Aluminum‐tolerant genotypes have roots with low CEC, and high Al activities (> 20 μM in the case of Grasslands Maku) are required to precipitate the relatively highly methylated pectins associated with low CEC. In contrast, relatively low activities of Al would precipitate the pectins in plants with roots of high CEC. This would decrease the protective capacity of the pectins, enabling the toxic, monomeric Al ions to come in contact with a number of Al‐sensitive compounds or processes in the cell wall, plasmalemma, or cell cytoplasm.     

铝、镉胁迫下不同大麦品种根际的铝、镉形态分析

为明确铝(Al)、镉(Cd)单独及复合胁迫下作物根际毒害元素的化学形态及其生物有效性,采用盆栽试验,以耐铝性不同的两个大麦品种(铝敏感品种浙农大9号和耐铝品种Day ten)为试验材料,利用连续提取法和ICP-AES方法分析了拔节期大麦根际的Al、Cd化学形态及其含量.结果表明,所有处理中大麦植株根际溶出Al均主要以毒性较小的酸溶无机Al和腐殖酸Al存在,根际Cd则主要以残留态形式存在.Al、Cd单独胁迫下大麦根际土壤溶液中各形态Al、Cd的溶出量均显著增加,交换态含量占可提取Al、Cd总量的比例增加.其中浙农大9号根际活性Al、Cd含量的增幅均大于Dayton.与单独Al或Cd处理相比,复合胁迫下根际交换态Al和Cd含量增加,其他形态含量下降或变幅不大.     

Mineralization and Nutrient Release of an Organic Fertilizer Made by Flour,Meat, and Crop Residues in Two Vineyard Soils with Different pH Levels

The mineralization and nutrient evolution of an organic fertilizer compost of flour, meat, and crop residues was evaluated in two vineyard soils. A lysimetric testing, using 2.2-L Büchner funnels, was carried out to study the evolution of pH, electrical conductivity, and nutrients during the 400-day experiment. The net mineralization for two different doses of the fertilizer mixed with the soils was compared with an unfertilized control. The pH value of the acidic soil decreased to values less than 4.5 because of the yield of hydrogen (H⁺) in the organic fertilizer mineralization, whereas the soluble aluminium (Al³⁺) increased quickly in the leachates. The mineralization process was quicker in the alkaline soil (with a maximum mineralization rate of 0.83 mg nitrogen (N) kg^?1 day^?1 for the 8 Mg ha^?1 dose and 0.43 mg N kg^?1 day^?1 for the 4 Mg ha^?1 dose) in comparison with the acidic soil, which reduced these rates up to 50%. The N-nitrate (NO₃) amounts yielded in a year were 150 and 79 kg N ha^?1 for the 8 and 4 Mg ha^?1 doses respectively in the alkaline soil, enough to cover the vineyard N demand. These values were reduced to 50% and 60% of N-NO₃ for the acidic soil, indicating the important effect of pH in the mineralization.     

Aluminum,Ca, and Mn Concentrations in Macadamia Seedlings as Affected by Soil Acidity and Liming

Abstract

Macadamia (Macadamia integrifolia) is increasingly becoming an important tree crop in many parts of the world. However, knowledge about the plant's nutritional behavior, especially under adverse soil conditions, has been deficient. To address this deficiency, a pot experiment was conducted to study the effects of Al, Mn and Ca (soil acidity and liming) on macadamia seedlings. Three soils having different mineralogy and fertility were used; soil pH was adjusted based on lime requirement curves so that several pH levels ranging from 4.5 to 7.5 were obtained for each soil. Chemical composition of the soil solution and of recently fully mature leaves was monitored periodically to assess the growth response.

Results suggested that Al was detrimental to physiological processes of macadamia seedlings when leaf Al was greater than 275 mg kg and soil‐solution Al exceeded 1.2 mg L^‐1. Furthermore, Al seemed to have reduced Mn uptake by the plant, although macadamia could accumulate as much as 1200 mg Mn kg^‐1 in leaves without apparent toxic symptoms. The internal Ca requirement of the plant was not clearly defined; however, maximum growth could be expected when soil solutions contained 160 mg Ca L^‐1 , which corresponded to 0.9 cmol(+)kg^‐1 of exchangeable Ca (or 10% of CEC) in a highly weathered Oxisol.     

Phytate Quantification using HPIC in the Presence of Iron and Aluminum

Phytate is an organic form of P that is difficult to analyze in complex matrices. To test if high concentrations of aluminum (Al) and iron (Fe) hinder accurate quantification of phytate in dairy manure and broiler litter when measured by high-performance ion chromatography (HPIC), researchers spiked dairy manure and broiler litter samples with Al, Fe, and phytate. Samples were alkaline extracted, acidified, and filtered, and then phytate spike recovery was analyzed with HPIC. High concentrations of Fe did not hinder phytate recovery in manure or litter samples. While phytate recovery was complete at typical manure and litter Al concentrations, high concentrations of Al inhibited phytate recovery in litter samples and in some manure samples. Overall, alkaline extraction of dairy manure and broiler litter and analysis with HPIC proved to be relatively accurate, fast, and cheap within normal Al and Fe ranges, compared to the commonly used nuclear magnetic resonance (NMR) method.     

Reactive aluminum in the vermont soil test

Abstract

Determination of Reactive Al by extracting a soil sample with pH 4.8 NH₄ OAc (1.25 N acetate) characterizes for northern acid soils the quantity of soil acidity that must be neutralized to meet lime need and also lower the P adsorbing capacity. Extracted Al is used in conjunction with pH in 10 mM CaCl₂ to calculate the lime requirement directly. First, the amount of P fertilizer needed is approximated, based on the P intensity (Available P) determined in the same NH₄ OAc extract. Then the recommended amount is increased by a P‐fixation factor obtained from the Reactive Al measured, and decreased by a Reserve P factor derived from fluoride extractable P.

Unlike a buffer lime requirement method, which predicts lime needed to reach a target pH, the Reactive Al test estimates the quantity of acidity that must be neutralized to prevent fixation of P fertilizer by soil Al and to release P from Al‐bound sources. Attaining a particular target pH is not the primary goal. The Reserve P test measures the amount of unavailable Al phosphates that becomes partially available when lime needs are met.     

Physiological and Proteomic Analyses Reveal Effects of Putrescine-Alleviated Aluminum Toxicity in Rice Roots

The effects of putrescine on improving rice growth under aluminum(Al) toxicity conditions have been previously demonstrated, however, the underlying mechanism remains unclear. In this study, treatment with 50 μmol/L Al significantly decreased rice root growth and whole rice dry weight, inhibited Ca~(2+) uptake, decreased ATP synthesis, and increased Al, H_2O_2 and malondialdehyde(MDA) contents, whereas the application of putrescine mitigated these negative effects. Putrescine increased root growth and total dry weight of rice, reduced total Al content, decreased H_2O_2 and MDA contents by increasing antioxidant enzyme(superoxide dismutase, peroxidase, catalase and glutathione S-transferase) activities, increased Ca~(2+) uptake and energy production. Proteomic analyses using data-independent acquisition successfully identified 7 934 proteins, and 59 representative proteins exhibiting fold-change values higher than 1.5 were randomly selected. From the results of the proteomic and biochemical analyses, we found that putrescine significantly inhibited ethylene biosynthesis and phosphorus uptake in rice roots, increased pectin methylation, decreased pectin content and apoplastic Al deposition in rice roots. Putrescine also alleviated Al toxicity by repairing damaged DNA and increasing the proteins involved in maintaining plasma membrane integrity and normal cell proliferation. These findings improve our understanding of how putrescine affects the rice response to Al toxicity, which will facilitate further studies on environmental protection, crop safety, innovations in rice performance and real-world production.     

麻竹竹叶提取物在HCl介质中对Al的缓蚀作用

[目的]研究麻竹竹叶提取物在HCl介质中对Al的缓蚀作用。[方法]采用失重法研究麻竹竹叶提取物在HCl溶液中对Al的缓蚀作用,并采用正交试验探索最佳的反应条件。[结果]麻竹竹叶提取物在HCl溶液中对Al具有良好的缓蚀作用,其最佳反应条件为HCl浓度0.6 mol/L,缓蚀剂浓度1.5 g/L,反应温度30℃,反应时间6 h,缓蚀率达64.3%。[结论]麻竹竹叶提取物在HCl溶液中对Al具有良好的缓蚀作用,可以作为一种环境友好型植物缓蚀剂。     

超声雾化大尺度合成球形AlN颗粒研究

以Al（NO3）3和CH3OH为反应原料,经超声雾化后与NH3在高温下制备AlN（氮化铝）颗粒,X射线显示所得到的AIN颗粒具有六方晶体结构,通过扫描电子显微镜（SEM）对制备的颗粒的形貌及尺寸分布进行分析,制备的AlN颗粒呈现的是类似球状的形貌,直径约在100～200nm,并且对不同前驱体制备的AlN粉末的形貌进行了分析,找到了能够制备类球状AlN粉末相对较好的前驱体溶液。