No abstract

Corn (Zea mays L.) is highly adaptable, but it has difficulties in expressing its productive potential in soils with high aluminum content, since this element is directly related to high acidity in the soil. The objective of this study was to evaluate the nitrogen compounds, proteins and amino acids of two corn cultivars subjected to increasing doses of aluminum. The experiment was carried out in a greenhouse using one of the corn plants from varieties BRS 106 and BRS 4157. The experimental design was entirely randomized, in a factorial design of 5x2, and the factors were composed of five doses of Al 3+ (0; 50; 100; 150 and 200 mmol L-1), with five repetitions. The variables analyzed were the concentration of nitrate, the activity of the nitrate reductase, concentration of ammonium, amino acids and proteins. There was a decrease in nitrate, activity of the Reductase enzyme of the Nitrate and protein in the highest dose of aluminum (200 mmol L-1) for both cultivars. There was an increase in ammonium and amino acids in the leaves of cultivars BRS 106 and BRS 4157. Cultivars BRS 106 and BRS 4157 were affected by the increasing doses of aluminum, but cultivar BRS 106 showed to be more tolerant.

RESUMO Thielaviopsis paradoxa é fungo do solo, patógeno amplamente distribuído em todo o mundo e capaz de infectar uma ampla gama de hospedeiros. Em palma de óleo é o agente etiológico da podridão basal, uma importante doença que pode causar sérios prejuízos devido à sua severidade e à rápida dispersão do patógeno. O trabalho teve como objetivo avaliar a patogenicidade e caracterizar um isolado de Thielaviopsis sp. em palma de óleo. O isolado de Thielaviopsis sp. foi obtido do estipe de plantas de palma de óleo, com aparentes sintomas de podridão. A patogenicidade foi avaliada em duas cultivares de palma de óleo, o híbrido interespecífico Manicoré e o híbrido intraespecífico Tenera. As mudas foram inoculadas por suspensão de conídios na concentração de 1x107 conídios por mililitro e discos de micélios, com e sem ferimentos na ráquis de folhas. O isolado foi cultivado em meio de cultura BDA para a caracterização morfológica. A análise filogenética foi realizada com base em comparação de sequências das regiões EF-1? e ITS com sequências disponíveis no GenBank-NCBI e analisadas no Mega 6.0. O isolado foi patogênico nas duas cultivares da palma de óleo em mudas previamente feridas, causando sintomas de podridão de coloração marrom, com formação de um halo amarelado na ráquis. Com o progresso da doença, as folhas apresentaram coloração amarelo progredindo para seca até a quebra da ráquis. O isolado de Thielaviopsis sp. apresentou crescimento rápido com velocidade de crescimento micelial de 50,76 mm dia-1 e com dois dias ocupou totalmente a placa de Petri de 90 mm. A colônia, de coloração inicialmente branca, tornou-se negra com a esporulação e produção de dois tipos de conídios: os endoconídios e aleuroconídios. Após as análises filogenéticas, foi possível comprovar a espécie Thielaviopsis ethacetica como agente etiológico da podridão basal da palma de óleo, distinguindo-a da espécie T. paradoxa.

We aimed to evaluate the changes in biochemical metabolism generated by salt stress and to investigate the effect of brassinosteroids in mitigating of this stress on two cultivars of Vigna unguiculata L. We used a completely randomized experimental design in a 2 x 3 x 3 factorial scheme, using two cultivars of cowpea (BRS Guariba and BR3 Tracuateua - moderately tolerant and sensitive to salinity, respectively), three concentrations of brassinosteroids (0, 0.2 and 0.4 μM Br) and three concentrations of NaCl (0 , 50 and 100 mM NaCl), with four replicates. The following evaluations were carried out: relative water content, electrolyte leakage, nitrate levels, nitrate reductase activity, free ammonium, total soluble amino acids, soluble proteins, glycine betaine and proline. The results showed that salinity at 100 mM affected the nitrate reductase enzyme activity, the relative water content, total soluble amino acids and soluble proteins for cultivars BR3 Tracuateua, and BRS Guariba, but the 24-epibrassinolid attenuated the effects of salinity for these variables. The concentration of 0.2 μM of Br increased 55% and 20% in proline and glycine betaine contents, respectively, in both of cultivars. The plants under stress saline and 0.2 mM of 24-epibrassinolid, presented 42% and 58% reductions in electrolyte leakage of BR3 Tracuateua and BRS Guariba cultivars, respectively. The concentrations of ammonium were slightly varied. Therefore, the application of 0.2 μM of 24-epibrassinolid caused a greater acclimatization of the cultivars, being the BR3 Tracuateua (sensitive to salt) cultivar more expressive in most treatments.

Due to rainfall and high temperatures, the Amazonian soil undergoes changes in its source material and leaching of base cations. This results in deep, infertile, and acidic soil. Aluminum present in acidic soil impairs plant growth and development by inhibiting root formation, enzymatic reactions, absorption, transport, and nutrient utilization. This study aimed to evaluate the effects of aluminum dosage on the metabolism of the oil palm Elaeis guineensis Jacq. The study was conducted in a greenhouse at the Federal Rural University of Amazonia. The experimental design was randomized, with five replications, in which dosages of 0, 10, 20, 30, and 40 mg L-1 aluminum chloride (AlCl3.6H2O) were administered. Electrolyte leakage, nitrate, nitrate reductase, free ammonium, soluble amino acids, proline content, and soluble proteins were analyzed in the leaves and roots of the oil palm. The highest concentration of aluminum was found in the roots. AlCl3 treatment at 40 mg L-1 increased electrolyte leakage, nitrate, ammonium, and proline concentrations in the roots, and amino acid concentrations in both the leaves and roots. Furthermore, a decrease in nitrate reductase enzyme activity was observed in the roots. This study demonstrates that the oil palm has mechanisms of tolerance to aluminum toxicity.