ABSTRACT The objective was to determine the growth and accumulation of macronutrients of two pineapple cultivars submitted to different concentrations of aluminum (Al). For this, a study was conducted in plastic pots containing 4 L of nutrient solution, in a randomized block design, in a 2 x 5 factorial scheme, corresponding to two pineapple cultivars (‘IAC Fantástico’ and ‘Vitória’) and five Al concentrations (0, 21.6, 43.2, 64.8 and 86.4 mg of Al plant-1), with four replicates. The following variables were evaluated: root length, dry matter of root, stem and leaf, stem diameter, number of leaves, chlorophyll content and accumulation of macronutrients at 60 days after treatment. The cv. ‘Vitória’ showed a linear decrease in chlorophyll content, root dry matter, root length and accumulation of N, P, K, Ca and Mg in most plant components promoted by the increase of Al concentration in the nutrient solution. The cv. ‘IAC Fantástico’ had lower total dry matter, stem dry matter, stem diameter and accumulation of N, Ca and Mg. However, the evaluated characteristics were not influenced by the increase of Al concentration, showing greater tolerance of this cultivar to Al in nutrient solution.

Young rubber plants were cultivated in BOLLE-JONES (1957) nutrient solutions. A separate aluminum solution was prepared by dissolving a aluminum foil with HC1 N. From this stock solution the following concentrations were prepared - none, 5, 10, 15, 20 and 25 ppm of aluminum. Plants were grown alternately for periods of 24 hours in these aluminum solutions and in the Bolle-Jones solution. This procedure was conducted for 95 days after which period the plants were harvested and divided into top whorl, 2nd and 3rd basal whorls, stem and roots. The material was dried and analysed for Ca, Mg and S. The concentration and accumulation of these plant nutrients were affected by levels over 15ppm of aluminum in the solution.

São realizados estudos termodinâmicos de nitretos, carbonetos e carbonitretos dos microelementos V, Nb, Al e Ti, utilizando bancos de dados computacionais do programa FactSage, com finalidade de verificar seus potenciais como inibidores do crescimento do grão na faixa de temperatura do processo de forjamento a quente dos aços. Um procedimento para verificação da solubilidade dos compostos dos microelementos por meio do FactSage foi desenvolvido e foram estudadas situações mais complexas e menos abordadas na literatura, tais como o efeito combinado de dois microelementos no aço e o estudo do comportamento dos carbonitretos em altas temperaturas com variantes do porcentual de carbono e nitrogênio. Os estudos demonstraram que os nitretos com presença de titânio possuem elevada estabilidade em altas temperaturas e, por isso, são potencialmente muito efetivos no controle do crescimento do grão. Alguns carbonetos com presença de nióbio apresentam também uma boa estabilidade em altas temperaturas, assim como os carbonitretos desses dois elementos. Foi verificada uma boa correlação dos produtos de solubilidade obtidos tanto por métodos experimentais como por cálculos termodinâmicos apresentados pela literatura, bem como a valiosa contribuição do software para estudos de precipitação e dissolução de carbonetos, nitretos e carbonitretos na austenita, permitindo auxiliar na seleção de aços e/ou modificação da composição de aços convencionais por meio da adição de microelementos juntamente com uma escolha apropriada de porcentuais de nitrogênio e/ou carbono, quando se busca controlar o crescimento do grão em altas temperaturas. Os resultados obtidos podem auxiliar de forma indireta nos estudos de eliminação de tratamentos térmicos convencionais, seja pelo uso de aços microligados com resfriamento controlado, seja pelo uso de aços convencionais de baixa liga temperados logo após forjamento, permitindo, assim, uma redução dos custos globais das peças. Além dessas considerações, os resultados apresentados e a técnica desenvolvida podem também ser úteis em outras áreas em que seja importante o controle do crescimento do grão, tais como laminação a quente e cementação em alta temperatura.

Al toxicity is one of the most important abiotic stresses that reduce the growth and development of plants. From a physiological standpoint, Al affects the activity of several important enzymes such as nitrate reductase, which is the gateway of nitrogen in plants, and also triggers nutritional disorders and reduced plant growth. The content of nitrogen compounds, macronutrients and growth were assessed in order to better understand how cowpea plants respond to the toxicity of Al in a nutrient solution. The study was conducted in a greenhouse in a completely randomized design, consisting of the concentrations of 0 and 1 mM of Al. After ten days of applying the treatments we evaluated the activity of nitrate reductase, concentrations of protein and total soluble amino acids, proline, ammonia, macronutrients, and dry weight of the shoots and roots. Al reduced the nitrate reductase activity (-16%), concentration of nitrate (-22%), protein (12%) amino acids (-14%) and proline (-66%), however the concentration of ammonia increased (27%). Similarly, among concentrations of macronutrients that of calcium was most reduced (-21%), followed by magnesium (-16%) phosphorus (-19%) and potassium (-18%). The production of shoot and root dry matter was reduced by 18 and 27% when applying Al. The cultivar of cowpea Pretinho precoce 1showed to be sensitive to Al toxicity as a result of its inability to promote a biochemical response and satisfactory nutritional production when subjected to Al toxicity, which justifies the need for adoption of liming processes in the production of this cowpea crop which is appreciated by small agricultural producers in the North and Northeast regions of Brazil.

Abstract Al and its alloys have a low atomic weight and high strength to density ratio. These properties make them very useful for the construction of parts in automotive industry, such as engine blocks or pistons. Al is prone to corrosion, due to its negative standard E of 1.66 V vs. NHE. In addition, Al corrosion resistance strongly depends on pH. Therefore, it is important to undertake a general study of Al corrosion behavior.

Se han realizado unos ensayos de campo de dos años de duración encaminados a la corrección de la acidez de un Typic Palexe­rult, de las formaciones de raña de la mese­ta norte de la provincia de León (España). El cultivo ensayado fue una variedad local de centeno, empleándose como materiales calizos en la enmienda del suelo el yeso, do­lomita, caliza y espumas de azucarería, con dosis de 6000 kg ha-1 de CaCO3 equivalente. Además de la analítica general, se determi­naron las formas de Al solubles y fácilmente intercambiables (Al-CaCl2), además del Al extraído con KCl y con BaCl2. Los modelos de regresión lineal múltiple de la producción total de biomasa demuestran que durante el primer año son el Al-CaCl2, pH y CICE los parámetros más explicativos de la varianza (R² = 0,82). Por el contrario, durante el segundo año de cultivo son el Al-KCl y el porcentaje de saturación de bases las varia­bles más correlacionadas con la producción (R² = 0,80).