Aluminium effects on the growth and mineral composition of corn plants cultivated in nutrient solution at low aluminium activity

L'article compare les élongations racinaires et la composition minérale de maïs tolérants et sensibles à la toxicité aluminiqu

Distribution and uptake of aluminium (Al) in the roots tips of Al-sensitive and Al-tolerant cultivars of corn (Zea mays L.) seedlings under metabolic and non-metabolic conditions

Cet article met en évidence le fait que la résitance des variétés de maïs à la toxicité aluminique provient d'un mécanisme d'exclusion de l'aluminium par les apex des racine

Effects of low aluminum activity in nutrient solutions on the organic acide concentrations in maize plants

The effects of low aluminum (Al) activity in nutrient solution on the concentrations of organic acids in two cultivars of maize (#Zea mays# L.), HS7777 Al-sensitive and C525-M Al-tolerant, were studied. Aluminum stress increased total organic acid concentration in the roots and in the shoots for both cultivars. The relative increase of t-aconitic, citric, formic, malic, and quinic acids was higher in the roots than in the shoots for both cultivars. The concentrations of c-aconitic, isocitric, malonic, oxalic, and succinic organic acids were reduced by Al stress, principally for C525-M. There were no consistent differences in organic acid concentrations between the cultivars to discriminate Al tolerance. The Al tolerance for C525-M may be justified by lower Al concentrations in the root tips where cellular division takes place and/or by higher excretion of organic acids from roots to the rhizosphere for detoxification of Al by chelation. (Résumé d'auteur

Uptake of aluminium by the root tips of an Al-sensitive and Al-tolerant cultivar of Zea mays

Uptake and compartmentation of Al in the roots tips were investigated in two corn (Zea mays L.) cultivars (HS7777 single sensitive hybrid and C525-M single tolerant hybrid). Seedlings were grown for 24 h in nutrient solution at pH 4.4 characterized by low ionic strength (2,06 microM) and low Al3+ activity (10.3 microM). The root elongation decreased strongly for the sensitive cultivar. There were no differences in the contents of total Al in the entire roots between cultivars. Nonexchangeable-Al and exchangeable-Al contents were higher in the root tips of HS7777. The sensitive cultivar also showed higher total and exchangeable-Al contents in excised root tips in 180 min of Al uptake. Al uptake for both cultivars increased in solution containing 0.1 mM of 2,4-dinitrophenol. Al contents were higher for the tolerant cultivar. (Résumé d'auteur

Estudios da fitotoxicidade de aluminio (AI) sobre plantas de milho (zea maysL.) cultividas em solucao nutritiva com fraça iônica e de altitudade de AI

L'article décrit la faisabilité de la technique de culture en solution nutritive de composition voisine de la solution du so

Effects of different calcium and sulfate concentrations in nutrient solutions on ionic strength values, aluminium 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 microM. 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 S04 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. (Résumé d'auteur

Trans and Saturated Alkyl Impurities in Technical-Grade Oleylamine: Limited Miscibility and Impacts on Nanocrystal Growth

Oleylamine (OLAm) is commonly used in nanocrystal synthesis as a 70% purity technical-grade reagent containing large amounts of trans and saturated alkylamine impurities. Large differences in the melting temperatures of these impurities point to the possibility that differences in their physical properties may impact nanocrystal synthesis and/or assembly. Although there is significant literature on the phase transitions and mixing behavior of fatty acids, much less is known about structurally equivalent amines, such as those in OLAm blends. Here, we synthesize isomerically pure OLAm and its trans isomer elaidylamine (ELAm), preparing controlled blends with the saturated analogue octadecylamine (ODAm). Phase diagrams of binary mixtures of OLAm/ELAm, OLAm/ODAm, and ELAm/ODAm reveal limited pairwise miscibility. Differential scanning calorimetry (DSC) of ternary mixtures illustrates distinct peaks for the trans and saturated impurities. We also show that ELAm and ODAm have two competing impacts on gold nanowire (AuNW) synthesis. Both impurities decrease modal (most common) AuNW length when representing as little as 5% of the ligand blend; ODAm decreases wire length more than ELAm. However, ELAm addition is also associated with increased populations of wire lengths ∼2× and 3× the modal wire length; conversely, blends with ODAm essentially eliminate these longer wires. We also find that ELAm and ODAm increase AuNW stability when present as part of the ligand blend

Propriedades físicas e taxa de estratificação de carbono orgânico num Latossolo Vermelho após dez anos sob dois sistemas de manejo Soil physical properties and organic carbon stratification rate in an oxisol after ten years under two different soil management systems

Nos solos de textura argilosa e muito argilosa, a compactação das camadas superficiais constitui uma das limitações do solo sob plantio direto. Nestas condições, tem sido adotado o revolvimento periódico do solo. As rotações de culturas são indicadas para o manejo físico do solo em razão do maior aporte de matéria orgânica e bioporosidade do solo. O objetivo deste trabalho foi quantificar, num Latossolo Vermelho eutroférrico, algumas propriedades físicas, os teores e a taxa de estratificação do carbono orgânico do solo (COS), após dez anos da instalação de dois sistemas de manejo do solo. Os sistemas de manejo de solo estudados foram: plantio direto com rotação de culturas (PD) e plantio direto com sucessão de culturas, realizando a escarificação do solo antes da semeadura da cultura de verão (PDR). Maiores valores de densidade do solo foram observados no PD e de macroporosidade e porosidade total no PDR. Nos dois sistemas, o volume de macroporos foi maior que 10 %, indicando que as condições de aeração foram adequadas para as raízes das plantas. A curva de retenção de água indicou que o PDR retém mais água que o PD em elevados potenciais, sendo similares para potenciais menores que -0,008 MPa. A resistência do solo à penetração (RP) foi maior no PD até à profundidade de 0,20 m, independentemente da umidade do solo. A partir dos resultados, verificou-se que, no PD, sob condições similares de secamento do solo, os valores de RP foram maiores do que no PDR, podendo atingir valores críticos ao crescimento das plantas. Assim, estratégias de manejo para conservar a umidade no solo são necessárias para manter a RP abaixo de valores impeditivos às plantas. Os teores de C-orgânico do solo foram maiores no PD até 0,10 m de profundidade, enquanto de 0,10-0,40 m, foram constatados maiores valores no PDR. A taxa média de estratificação de COS foi de 1,73 no PD, enquanto no PDR foi de 1,24. Os resultados evidenciam que a maior concentração de COS no PD pode resultar em condições físicas mais estáveis às culturas.<br>In the clay and heavy clay soils, compaction of the surface layer represents one of the limitations under no-tillage. Under such conditions, periodic soil tillage has been adopted. Other techniques, such as crop rotation are indicated for the physical management of the soil due to a larger input of organic matter and bioporosity of the soil. The objective of this study was to quantify some soil physical properties in an eutroferric Red Latosol (rhodic Eutrudox), the organic carbon content and the soil organic stratification rate after ten years of two soil management systems. The soil management systems included: crop rotation under no-tillage (NT), and crop-sucession under no-tillage, but with soil chiseling before the summer crop (CNT). Larger values of bulk density were verified in NT and macroporosity and total porosity in CNT. In both management systems, the air-filled porosity was above 10 %, suggesting that the aeration conditions were appropriate for the plant roots. The soil water retention curve indicated that the soil under CNT retains more water than under NT at high potentials, but they are similar at potentials below -0.008 MPa. The soil penetration resistance (RP) was larger in NT down to the depth of 0.20 m, independently of the soil moisture content. Results suggested that with identical soil dryness the RP can reach restrictive values for plant growth in NT. Thus, management practices to maintain the soil moisture are necessary to keep the RP lower than the levels considered restrictive for plants. The soil organic content (SOC) was higher in NT down to a depth of 0.10 m, while higher values were observed at depths of 0.10-0.40 m in CNT. The SOC stratification rate in the soil was 1.73 in NT while in CNT it was 1.24. Results show that this highest SOC concentration in NT may result in more stable soil physical conditions for crops