Leandro Torres de Souza

Doses e formas de aplicação de nitrogênio no desenvolvimento e produção da cultura do trigo

Objetivou-se avaliar o efeito de doses e formas de aplicacao de nitrogenio sobre o desempenho e producao de duas cultivares de trigo. O experimento, conduzido em Vicosa-MG, de maio a setembro de 2005, foi instalado segundo um esquema fatorial 2x2x5 no delineamento de blocos casualizados, com quatro repeticoes. Os tratamentos avaliados consistiram da combinacao das cultivares de trigo, BRS 210 e Pioneiro, duas formas de aplicacao de adubo nitrogenado (dose total aplicada por ocasiao da semeadura ou 20 kg ha-1 na semeadura e o restante em cobertura no inicio da fase de perfilhamento) e cinco doses de nitrogenio (40, 60, 80, 100 e 120 kg ha-1) tendo como fonte o sulfato de amonio. A cultivar Pioneiro apresentou maior potencial produtivo que a cultivar BRS 210, mas foi menos resistente ao acamamento. O parcelamento da adubacao nitrogenada proporcionou maior acamamento e nao trouxe beneficios a produtividade dos graos. As doses de N promoveram resposta quadratica da produtividade dos graos, com ponto de maxima estimado na dose de 96,8 kg ha-1 e, aumento linear do acamamento de plantas da cultivar Pioneiro.

Effect of Nitrogen and Trinexapac-Ethyl Rates on the SPAD Index of Wheat Leaves

ABSTRACT The objective of this study was to evaluate the effect of nitrogen (N) and trinexapac-ethyl (TE) rates on the SPAD index in wheat flag leaf. The treatments were five N rates (30, 60, 90, 120, 150 kg ha−1) combined with four TE rates (0, 63, 125, 188 g ha−1). The experiment was carried out in a randomized block design with four repetitions. SPAD index, leaf N content and grain yield showed quadratic response to the increase in N rates, whereas area, wet and dry weight of flag leaf presented linear increase. TE caused linear increase in SPAD index, linear decrease in leaf area, reduction in grain yield with smaller N rates and increase with larger N rates. The N content, and the wet and dry weight of flag leaf were not affected by TE. SPAD calibration to estimate N status in wheat should be specific for each TE rate.

Rates of nitrogen and growth retardant trinexapac-ethyl on wheat

The objective in this study was to evaluate the effects of nitrogen rates in association with rates of the growth retardant trinexapac-ethyl on wheat. The experiment was conducted in Vicosa, MG and arranged in a 5×4 factorial, randomized block design, with four repetitions. A combination of five nitrogen rates (30, 60, 90, 120 and 150kg ha-1) with four rates of trinexapac-ethyl (0, 62.5, 125 and 187.5g ha-1) were tested. Trinexapac-ethyl promotes reduction of soot dry mass and grain yield at the lowest N rates, but at the highest N rates there is increase in these characteristics. The combination between N and trinexapac-ethyl rates that promotes higher shoot dry mass is 150kg ha-1 and 187g ha-1 but that promotes higher grain yield is 100kg ha-1 and 120g ha-1, respectively.

In vitro germination of beetroot seeds treated with Ga3 and sucrose

The objective of this study was to evaluate the in vitro germination of beetroot seeds, cv. Early Wonder Tall Top, treated with gibberellic acid and sucrose at different concentrations. A randomized complete block design in a 2 x 5 factorial arrangement with ?ve replications was used. The beetroot seeds ware presoaked in gibberellic acid (GA 3 ) and destilated water during six hours, maintained of ?ve concentration of culture medium (0, 15, 30, 45, 60 g L -1 ). Seeds treated with GA 3 and maintained in medium with sucrose in the concentrations of 15 g L -1 presented the highest germination, while seedlings with the highest vigor were obtained with seeds maintained in the medium at 15 and 30 g L -1 of saccharose.

COMPARAÇÃO DE METODOLOGIAS DO TESTE DE TETRAZÓLIO PARA SEMENTES DE CAFEEIRO

O teste de tetrazolio apresenta-se como uma alternativa promissora para a avaliacao rapida da viabilidade das sementes, sendo que para cafeeiro ha duas metodologias descritas. O presente trabalho teve como objetivo verificar, entre estas metodologias existentes, qual a mais eficiente para a determinacao rapida da viabilidade e do vigor. Para tal, sementes de 4 lotes foram submetidas as seguintes metodologias: 1) embebicao por 24 horas a 30 oC; corte da porcao do endosperma que contem o embriao; exposicao desta porcao a solucao de tetrazolio a 0,1%, durante 16 horas a 35 oC, retirando em seguida o embriao com ajuda de um bisturi para posterior avaliacao; 2) embebicao por 24 horas a 30 oC; retirada do embriao e exposicao a solucao de tetrazolio a 0,1%, durante 16 horas a 35 oC, para posterior avaliacao. Para comparacao dos resultados obtidos foi montado o teste de germinacao, avaliando-se a porcentagem final de germinacao e o vigor (1a contagem de germinacao). Os resultados indicaram que a metodologia 2 mostrouse mais promissora para a avaliacao da viabilidade e do vigor de sementes de cafeeiro, pois os valores obtidos se equivaleram aos valores do teste de germinacao. A metodologia 1 nao foi eficiente pois apresentou problemas quanto a coloracao dos embrioes, gerando assim duvida durante a avaliacao da viabilidade das sementes.

Effects of aluminum on the elongation and external morphology of root tips in two maize genotypes

The objective of this study was to evaluate the effects of toxic levels of aluminum (Al) on the growth and external morphology of root tips in two maize genotypes with differential Al tolerance. The maize genotypes UFVM-100 (Al-sensitive) and UFVM-200 (Al-tolerant) were treated with 0 and 50 mM Al in a 0.5 mM CaCl2 solution at pH 4.5; root elongation, Al content and the external morphology of the root tips were evaluated. Chemical analysis, hematoxylin staining and energy dispersive X-ray spectrometry (EDS) showed greater Al accumulation in the root tips of the UFVM-200 genotype. The inhibition of root elongation in the UFVM-100 genotype, however, was much stronger than in the UFVM-200 genotype. Both maize genotypes exhibited visible and intense alterations in external micromorphology of the root tip, especially the Al-sensitive UFVM-100 genotype. Scanning electron micrographs showed intense cell disorganization and transverse ruptures of the protodermic and outer cortex layers of the cells in both genotypes. The ruptures were deeper and wider and reached the inner cortex layers in the UFVM-100 genotype. The EDS analysis showed that, in addition to Al accumulation, there was a proportional increase in the P concentration in the root tips of the UFVM-200 genotype. This is indicative of possible precipitation and/or immobilization of Al in the root tip apoplast of this genotype, which contributes to symplastic detoxification.

Growth retardants in wheat and its effect in physiological quality of seeds

Plant lodging in wheat has been controlled through growth retardants. However, there is lack of information on the effect of these products on the physiological quality of seeds. The objective of this study was to evaluate the physiological quality of wheat seeds obtained under different rates and application times of three growth retardants. The trial was carried out in Vicosa-MG, from May to September 2005, in a factorial and hierarchical scheme, in randomized block design with four replications and a control treatment. The treatments consisted of 500, 1000 and 1500g ha-1 of chlormequat; 40, 80 and 120g ha-1 of paclobutrazol and 62.5, 125 and 187.5g ha-1 of trinexapac-ethyl applied at the 6 or 8 growth stage based on the scale of Feeks and Large, and a control treatment without growth retardant application. Leaf application of growth retardants as chlormequat, paclobutrazol and trinexapac-ethyl did not affect the germination and vigor of wheat seeds.

GERMINAÇÃO E VIGOR DE SEMENTES DE CENOURA EM SOLO DE MINERAÇÃO DE CALCÁRIO SOB DIFERENTES INTENSIDADES LUMINOSAS E ADUBAÇÕES

Dentre as condicoes ideais para germinacao, o tipo de solo e muito importante, pois, interfere nao apenas na germinacao das sementes mas, tambem, no desenvolvimento pos-seminal. Alem da adubacao, outro fator importante na emergencia e crescimento das mudas e a luminosidade devido sua influencia em processos como a fotossintese. Neste trabalho, objetivou-se avaliar a influencia da adubacao com esterco bovino, torta de filtro e vinhaca, bem como da luminosidade na germinacao e vigor de sementes de cenoura, em solo de mineracao de calcario. O experimento foi conduzido em casa de vegetacao, em 2005, em Alegre-ES. Utilizou-se o delineamento inteiramente casualizado, em arranjo fatorial 13 x 3 (adubacoes x luminosidades) e 4 repeticoes. Os tratamentos constaram de solo de mineracao de calcario enriquecido ou nao com adubacao e 3 niveis de luminosidade. A adubacao teve influencia direta nas plântulas, pois, as menores intensidades (13.8 µmol fotons m-2s-1) aumentaram a germinacao e altura destas, enquanto as maiores intensidades (1192.8 µmol fotons m-2s-1) aumentaram a velocidade de germinacao e o acumulo de materia seca. A adubacao com os 3 materiais orgânicos e NPK proporcionou maior altura e materia seca as plantas.