Nitrogen supply affects root and shoot amino acid composition in Eucalyptus clones

Abstract Changes in amino acid composition are frequently observed in plants under various conditions of stress, such as nutrient deficiencies. Hence, amino acids have been proposed as more sensitive indicators of N status than total N concentration. The goal of this study was to evaluate alterations in amino acid composition of young eucalyptus clones as a result of variable N supply. An experiment was carried out in a greenhouse with two Eucalyptus clones (VM-01 and I-144) and six N application rates (0, 0.74, 2.93, 4.39, 5.85, and 8 mmol L -1 of NH 4 NO 3 ) grown in a nutrient solution in a randomized block design. Amino acid concentrations varied greatly as a function of N supply and depended on the organ (root or leaf) and the genotype evaluated. Roots showed greater number of amino acids than leaves (17 and 14, respectively), probably because of a higher amino acids synthesis or translocation to the roots. For both clones, N deficiency induced a significant decrease in proline, arginine, and methionine concentration in roots and a decrease in tyrosine, alanine, threonine, and methionine in leaves. These decreases were also associated with lower total N concentration and total dry matter of the eucalyptus clones. In conclusion, N supply affects amino acid composition, and the amino acids listed above are likely to be more sensitive indicators of N status than total N in eucalyptus clones

Boro: nada entediante acerca deste intrigante elemento

Although Boron (B) is an essential micronutrient for plant growth and development, both deficiency and toxicity of B are important problems that severely affect agricultural production. This fact aside, the impact of these stresses in plants are still poorly understood. Thus, plants may respond differently to B availability through local and systemic signaling, whose mechanisms are yet poorly understood. Previous studies further suggest that ethylene plays a key role in the responses induced by B deficiency in the root system. The main goal of this work was to better understand the physiological and metabolic mechanisms underlying stress caused by B deficiency and excess, as well as to better understand the connections between ethylene and B in modulating plant growth. For this purpose, the responses of different conditions of B availability (deficiency, adequate and toxicity) were investigated in Arabidopsis and ethylene mutant tomato (Solanum lycopersicum) plants. The results obtained in this work demonstrate physiological and metabolic alterations in response to the contrasting conditions of B and that these responses are likely able to generate energy and maintain normal growth in B deficiency. It was also observed an association between B and ethylene levels mediating physiological and metabolic changes. Finally, our study sheds light on the complex relationship between B and ethylene and their overall effects on plant growth and development. The results described here helps to understand the plant's response mechanism to B deficiency and excess, and paves way for identifying the signaling pathways and genes involved in homeostasis and B accumulation in tissues. Although the absence of alterations in plant growth coupled with changes in fruit yield and seed production observed in response to change in the levels of ethylene is somewhat surprising it is tempting to speculate that pathways of energy metabolism and hormone metabolism are most likely highly interconnected at the whole plant level in a manner that allows the plant to prioritize reproductive organs during senescence under B stressfully conditions. It will be important to establish the functional significance of this observation in future studies in order to fully understand the molecular regulatory hierarchy regulating ethylene balance at the whole-plant level, particularly in response to fluctuations in B levels. Key-words: B deficiency, B toxicity, Ethylene, Central Metabolism.Embora o Boro (B) seja um micronutriente essencial para o crescimento e desenvolvimento das plantas, juntamente com o fato de que tanto a deficiência quanto a toxicidade são problemas importantes que afetam severamente a produção agrícola, o impacto dessas tensões nas plantas ainda é pouco conhecido. Assim, as plantas podem responder diferentemente à disponibilidade de B por meio de sinalização local e sistêmica, cujos mecanismos ainda são pouco compreendidos. Estudos anteriores sugerem também que o etileno desempenha um papel fundamental nas respostas induzidas pela deficiência de B no sistema radicular. O principal objetivo deste trabalho foi entender melhor os mecanismos fisiológicos e metabólicos em resposta a deficiência e excesso de B, bem como entender melhor as conexões entre etileno e B na modulação do crescimento das plantas. Para tanto, foram investigadas as respostas de diferentes condições de disponibilidade de B (deficiência, adequada e toxidez) em plantas de Arabidopsis e tomateiro (Solanum lycopersicum) mutantes em etileno. Os resultados obtidos neste trabalho demonstram alterações no crescimento, ocorrem alterações fisiológicas e metabólicas em resposta às condições contrastantes de B e que essas respostas provavelmente são capazes de gerar energia e manter o crescimento normal na deficiência de B. Também foi observada associação entre os níveis de B e etileno, mediando alterações fisiológicas e metabólicas. Finalmente, nosso estudo lança luz sobre a complexa relação entre B e etileno e seus efeitos gerais no crescimento e desenvolvimento das plantas. Os resultados deste estudo ajudam a entender o mecanismo de resposta da planta à deficiência e ao excesso de B e abre caminho para identificar as vias de sinalização e os genes envolvidos na homeostase e no acúmulo de B nos tecidos. Embora a ausência de alterações no crescimento das plantas juntamente com as mudanças na produção de frutos e na produção de sementes observadas em resposta à mudança nos níveis de etileno seja algo surpreendente, é tentador especular que as vias do metabolismo energético e do metabolismo hormonal estão provavelmente altamente interconectadas ao nível de planta inteira de uma maneira que permita à planta priorizar os órgãos reprodutivos durante a senescência sob condições estressantes B. Será importante estabelecer o significado funcional dessa observação em estudos futuros para entender completamente a hierarquia molecular que regula o balanço de etileno em todo o nível da planta, particularmente em resposta as flutuações nos níveis de B. Palavras-chave: Deficiência de B, Toxidez de B, Etileno, Metabolismo CentralConselho Nacional de Desenvolvimento Científico e Tecnológic

Soil nitrogen transformations and sugarcane response to nitrogen fertilization as related to sunn hemp rotation

O plantio de adubos verdes na renovação do canavial constitui importante fonte de nutrientes, principalmente nitrogênio (N), possibilitando redução no uso de fertilizante nitrogenado. A hipótese deste trabalho é de que a rotação com Crotalaria irá aumentar a disponibilidade de N no solo e diminuir a resposta da cana-planta ao N. Objetivou-se avaliar a dinâmica do N no solo em área com e sem rotação com crotalária e seu potencial na redução da adubação nitrogenada de plantio. Foram instalados dois experimentos em Iracemápolis, SP, em um Nitossolo Vermelho Eutroférrico Latossolico, em delineamento de bloco casualizados com quatro repetições. No primeiro experimento, utilizou-se rotação com crotalária e, no segundo, a área foi deixada em pousio. No plantio da cana-planta (abril de 2013) foram aplicados os tratamentos controle (sem N), 30, 60, 90 e 120 kg ha-1 de N, na forma de nitrato de amônio no sulco de plantio. A cada dois meses realizou-se coleta de solo para determinação dos teores de N mineral (N-NH4+ e N-NO3- + N-NO3-) e fração hidrolisável do N orgânico (pelo método do Illinois Soil Nitrogen Test-ISNT). Mensalmente avaliou-se o número de perfilhos e, aos seis meses após o plantio, foram avaliados os teores de N total, N-NH4+ e N-NO3- e índice SPAD. Na colheita da cana-planta (julho de 2014) foram realizadas avaliações de produtividade, atributos tecnológicos, acúmulo de N e análises microbiológicas do solo. A rotação com crotalária aumentou o perfilhamento da cana-de-açúcar nos primeiros meses após o plantio. Nas folhas houve predomínio de N na forma de N-NH4+ em relação a N-NO3 e a rotação com crotalária aumentou a concentração foliar de N-NH4+. Não houve efeito da rotação com crotalária e nem das doses de N no acúmulo de N na cana-de-açúcar. Houve resposta às doses de N aplicadas no plantio somente na área sem rotação com crotalária. Apesar dos teores de N mineral no solo e N-ISNT não terem aumentado com a rotação com crotalária, o cultivo desta leguminosa aumentou a disponibilidade do N no solo, o que pode ser verificado pela ausência de resposta à adubação nitrogenada na área com rotação. A rotação com crotalária em cana-de-açúcar tem potencial de aumentar a produtividade e reduzir o uso de adubos nitrogenados no plantio da cana-de-açúcar, contribuindo para sustentabilidade do sistema.The establishment of cover crops in rotation with sugarcane is an important source of nutrients, mainly nitrogen (N), showing potential to reduce N fertilization requirements by sugarcane. This study hypothesized that sunn hemp rotation with sugarcane will increase soil N availability and reduces sugarcane (cane-plant) response to N fertilization. The objective was to evaluate soil N dynamics in areas subjected or not to rotation, and the potential in reducing N fertilization at sugarcane planting. Two field trials were set up in Iracemápolis, SP, in a Rhodic Kandiudox, in a complete block experimental design with four repetitions. In the first trial, sunn hemp was sowed and in the second trial, the field was left without cover crops. At sugarcane establishment (April 2013) the treatments were applied: control (without N), 30, 60, 90 e 120 kg ha-1 of N, as ammonium nitrate applied at the borrow of the furrow. Soil sampling was performed bi-monthly to evaluate soil inorganic N content (N-NH4+, and N-NO3- + N-NO2-) and hydrolysable soil N (Illinois Soil Nitrogen Test - ISNT). Sugarcane sprouting was recorded monthly and, after six months from planting, sugarcane leaves were collected to determine total N, N-NH4+, N-NO3-, and SPAD index. At cane-plant harvest (July 2014), the stalk yield was recorded, as well as quality parameters, N uptake, and soil microbiological analysis. Sunn hemp rotation increased sugarcane sprouting during initial growth stages. In sugarcane leaves the amount of N-NH4+ is higher than N-NO3-, and sunn hemp rotation increased N-NH4 content in the leaves. However, there was no effect of rotation or N rates in N uptake by sugarcane. Sugarcane yield increased with N fertilization only in the area without rotation. Besides soil inorganic N and ISNT content did not increases with rotation, the use of sunn hemp increased the availability of soil N to sugarcane, since the rotation reduced sugarcane response to N fertilization. Rotation of sunn hemp in sugarcane field showed potential in increasing yield and reducing N fertilization at planting, contributing to the sustainability of sugarcane production

Alumínio estimula o crescimento radicular de erva-mate?

A toxicidade por Al em plantas se dá de várias maneiras, sendo a inibição do crescimento radicular uma das primeiras a se expressar, embora não seja prontamente perceptível em razão do hábito de crescimento das raízes. O objetivo desse trabalho foi avaliar a tolerância da erva-mate ao Al por meio do crescimento de raízes de mudas submetidas a doses crescentes do elemento. Para isso, testaram-se, três clones (C1, C2 e C3), doses de 100, 500, 1.000 e 2.000 μmol L-1 de Al (AlCAlCl36H2O) e um controle sem Al. Após 50 dias, determinaram-se massa seca das raízes, comprimento e volume total do sistema radicular, comprimento e volume total das raízes em diferentes diâmetros. O Al influenciou positivamente o crescimento das raízes de todos os clones. O maior comprimento radicular foi apresentado pelo clone C2, seguido pelo C3 e C1 em doses superiores a 1.500 μmol L-1. Os maiores volumes foram obtidos para os clones C3, C2 e C1 nas doses respectivas de 2.000, 1.355 e 1.988 μmol L-1 de Al. Maiores comprimentos e volume radicular foram provenientes de raízes finas em doses superiores a 1.500 μmol L-1 de Al. O Al estimula o crescimento radicular e os clones testados apresentam tolerância diferencial ao Al.Aluminum toxicity can affect various plant processes; mainly root development which is not easily observed due to root growth habit. The objective was to evaluate root growth of mate when subjected to increased Al concentrations in the nutrient solution. Seedlings of three mate clones (C1, C2 and C3) were grown in nutrient solution added with 0, 100, 500, 1,000 and 2,000 μmol L -1 Al (AlCl 3 .6H 2 O) and a control without Al. Fifty days after transferring the plants to these solutions, dry matter of root, length and volume of roots of different diameters were evaluated. Al increase promoted root growth of all clones. Highest root length was observed for C2, followed by C3 and C1, for Al concentrations higher than 1,500 μmol L -1 . The higher volumes were obtainedby the clones C3, C2 and C1 with Al concentration off 2,000, 1,355 and 1,988 μmol L -1 , respectively. The smaller root volume of C2 was obtained for Al concentration of 1,355 μmol L -1 . The best fine root growth (dry matter and length) was obtained in Al concentrations above 1,500 μmol L -1 . The results indicate that Al stimulates mate root growth, and the magnitude of Al tolerance is clone dependen

Differential Behavior of Young Eucalyptus Clones in Response to Nitrogen Supply

Eucalyptus requires large amounts of nitrogen (N); however, it responds in diverse manners to the application of this nutrient. The aim of this study was to evaluate the differential performance in growth, mineral nutrition, and gas exchanges of N-fertilized Eucalyptus clones. The treatments consisted of two Eucalyptus clones (VM-01 and I-144) and six N application rates (0, 0.74, 2.93, 4.39, 5.85, and 8 mmol L-1 NH4NO3) arranged in a randomized complete block design with five replications. VM-01 had greater plant height and greater height/collar diameter ratio, as well as higher leaf concentrations of all macronutrients and of Cu, Fe, Mo, and Zn. In terms of total and root dry matter production, root/shoot ratio, and collar diameter, as well as stomatal conductance and transpiration, I-144 performed better. The performance of the clones was clearly differentiated, and the growth of I-144, despite lower leaf N concentration, was in general better than VM-01

Effect of potassium fertilization on yield and nutrition of yerba mate (Ilex paraguariensis)

Yerba mate (Ilex paraguariensis) is a tree species native to the subtropical regions of South America, and is found in Brazil predominantly in the southern region. Despite the historical importance in this region, so far, studies on crop nutrition to improve yields are scarce. Thus, this study evaluated the effect of potassium rates on K soil availability, and the yield and nutritional status of yerba mate. The experiment was conducted in São Mateus do Sul, State of Paraná, on a Humox soil, where K2O rates of 0, 20, 40, 80, 160, and 320 kg ha-1 were tested on 7-year-old plantations. The experiment was harvested 24 months after installation by removing approximately 95 % of the canopy that had sprouted from the previous harvest. The soil was evaluated for K availability in the layers 0-10, 0-20, 10-20, and 20-40 cm. The plant parts leaf fresh matter (LM), twigs (TW), thick branches (BR) and commercial yerba mate (COYM), i.e., LM+TW, were analyzed. In addition, the relationship between fresh matter/dry matter (FM/DM) and K concentration in LM, AG and BR were evaluated. The fertilization increased K availability in all evaluated soil layers, indicating good mobility of the nutrient even at low rates. Yerba mate responded positively to increasing K2O rates with higher yields of all harvested components. The crop proved K-demanding, with a maximum COYM yield of 28.5 t ha-1, when 72 mg dm-3 K was available in the 0-20 cm layer. Yerba mate in the plant production stage requires soil K availability at medium to high level; in clayey soil with low K availability, a rate of 300 kg ha-1 K2O should be applied at 24 month intervals to obtain high yields. A leaf K concentration of 16.0 g ha-1 is suitable for yerba mate in the growth stage