Christian Bredemeier

Regulação da absorção e assimilação do nitrogênio nas plantas

A presente revisao tem por objetivo discutir os mecanismos de regulacao da absorcao e assimilacao do nitrogenio nas plantas, de modo que a eficiencia de uso desse nutriente seja aumentada. O nitrogenio e absorvido nas raizes sob a forma de NO3 ou NH4 , sendo entao incorporado em aminoacidos na propria raiz ou na parte aerea. A taxa e a quantidade de nitrogenio absorvido e assimilado durante o ciclo da planta dependem da presenca de carregadores especificos na membrana plasmatica, da atividade das enzimas envolvidas no seu ciclo, da disponibilidade de energia necessaria para os processos de absorcao e assimilacao e do estadio de desenvolvimento da planta. Inumeros grupos de pesquisa tem centrado esforcos na identificacao dos pontos mais limitantes do metabolismo do nitrogenio nas plantas. Os limitadores tem sido relacionados com: a) a afinidade dos carregadores pelo nitrato e amonio; b) o suprimento de carboidratos as raizes; c) o nivel de aminoacidos no floema radicular; d) a atividade das enzimas redutase do nitrato (RN), sintetase da glutamina (GS) e sintase do glutamato (GOGAT); e) a fonte de N suprida as plantas (NO3 ou NH4 ); f) o local de assimilacao do N (raiz ou parte aerea). Esses estudos tem mostrado que o metabolismo do N e multiregulado e integrado ao metabolismo geral da planta. A identificacao de pontos metabolicos especificos que sao mais limitantes para o incremento da produtividade e complexa. A perspectiva e que a clonagem dos transportadores de N podera auxiliar os programas de melhoramento genetico na obtencao de plantas mais eficientes na absorcao do nitrogenio.

Modelo para estimativa do potencial produtivo em trigo e cevada por meio do sensor GreenSeeker

Areas with different yield potential within a field need to be managed separately as for nitrogen application in small grain cereals. Terrestrial remote sensing-based equipment such as the GreenSeeker sensor is one of the tools available to handle different management zones. To do this, the sensor allows the definition of classes to estimate yield potential. A model which correlated the Normalized Difference Vegetation Index (NDVI) to shoot dry biomass at the 6-leaf-stage was developed for estimating yield potential classes for wheat and barley. The model eliminated differences between species and cultivars as no correction for these factors is necessary. The effects of surface background (corn or soybean crop residues) were considered in this model. When readings are carried out before or after the recommended period, the model can be adjusted for under or overestimation. Spatial variability analysis may evaluate if yield potential zones estimated by the NDVI classes proposed in the model are related to spatial variability of shoot biomass, N rates applied and grain yield.

Expression of an osmotin-like protein from Solanum nigrum confers drought tolerance in transgenic soybean

BackgroundDrought is by far the most important environmental factor contributing to yield losses in crops, including soybeans [Glycine max (L.) Merr.]. To address this problem, a gene that encodes an osmotin-like protein isolated from Solanum nigrum var. americanum (SnOLP) driven by the UBQ3 promoter from Arabidopsis thaliana was transferred into the soybean genome by particle bombardment.ResultsTwo independently transformed soybean lines expressing SnOLP were produced. Segregation analyses indicated single-locus insertions for both lines. qPCR analysis suggested a single insertion of SnOLP in the genomes of both transgenic lines, but one copy of the hpt gene was inserted in the first line and two in the second line. Transgenic plants exhibited no remarkable phenotypic alterations in the seven analyzed generations. When subjected to water deficit, transgenic plants performed better than the control ones. Leaf physiological measurements revealed that transgenic soybean plants maintained higher leaf water potential at predawn, higher net CO2 assimilation rate, higher stomatal conductance and higher transpiration rate than non-transgenic plants. Grain production and 100-grain weight were affected by water supply. Decrease in grain productivity and 100-grain weight were observed for both transgenic and non-transgenic plants under water deficit; however, it was more pronounced for non-transgenic plants. Moreover, transgenic lines showed significantly higher 100-grain weight than non-transgenic plants under water shortage.ConclusionsThis is the first report showing that expression of SnOLP in transgenic soybeans improved physiological responses and yield components of plants when subjected to water deficit, highlighting the potential of this gene for biotechnological applications.

DISPONIBILIDADE DE NITROGÊNIO E SUA RELAÇÃO COM O AFILHAMENTO E O RENDIMENTO DE GRÃOS DE AVEIA

Nitrogen shows a strong influence on oat growth and development, mainly on early stages of plant cycle. Oat tiller number and survival and grain yield as affected by nitrogen supply was studied in five field experiments at Estacao Experimental Agronomica/UFRGS (Eldorado do Sul, RS), from 1993 through 1998, with cultivars UFRGS 10 and UFRGS 15. Treatments consisted in applying N in different plant stages (emergence to booting) or in different levels at plant emergence. In all situations, treatments received or not an extra N-supply at the 7th leaf stage. Tillering was stimulated mainly by N applied at plant emergence for tiller emission and by N applied at the 7th leaf stage which reduced tiller mortality and mantained synchrony between main stem and tiller development. The best grain yields were obtained when N was available from emergence up to 7th leaf stage. Late N application (booting stage) resulted in no yield increase. When soil nitrogen supply is restricted, N should be applied at sowing and 7th leaf emission.

Produtividade de arroz irrigado e eficiência da adubação nitrogenada influenciadas pela época da semeadura

The potential grain yield of late flooded rice is important for decision making of producers. Yields of rice crops sown after the recommended period are restricted due to unfavorable climatic conditions. The objective of this research was to evaluate grain yield and agronomic, technical and economic efficiency of broadcast nitrogen for flooded rice sown in December in the state of Rio Grande do Sul, Brazil. The field experiment was carried out in 2005/2006, in Cachoeirinha. Treatments consisted of two sowing dates, recommended (November) and late (December), four seeding rates (50, 100, 150, and 200 kg ha-1) and four nitrogen levels (0, 60, 120, and 180 kg ha-1). The experiment had a randomized block design using split plots with three replications. Rice grain yield and response to nitrogen topdressing were reduced by the late sowing date. The doses for maximum technical and economic efficiency were reduced with the sowing delay, and nitrogen agronomic efficiency was reduced with the sowing delay and N fertilizer dose. The number of panicles m-2 did not respond to nitrogen broadcast and was one of the most limiting yield components.

Densidade de plantas de milho híbrido em semeadura precoce no Rio Grande do Sul

A escolha da densidade de plantas e a sua adequacao a epoca de semeadura sao praticas de manejo importantes na determinacao do rendimento de graos de milho. Este trabalho foi realizado a fim de avaliar os efeitos da densidade de plantas sobre o rendimento de graos e seus componentes em dois hibridos cultivados em semeadura precoce (agosto) no Rio Grande do Sul. O experimento foi conduzido em Eldorado do Sul, em 2006/07. Os tratamentos consistiram de quatro densidades de plantas (5,5; 7,3; 9,1 e 11pl m-2) e dois hibridos, um de folhas decumbentes (Dow 2B587) e outro de folhas eretas (NB 4214). A semeadura foi realizada em 22 de agosto de 2006. O rendimento de graos do hibrido de folhas decumbentes aumentou linearmente com o incremento na densidade de 5,5 ate 11pl m-2, alcancando 16t ha-1. Ja no hibrido de folhas eretas, o rendimento aumentou de forma quadratica, sendo maximizado na densidade de 9,4pl m-2. O numero de espigas por metro quadrado foi o componente que melhor explicou o aumento da produtividade com o incremento na densidade de plantas. O uso de densidades superiores a 9pl m-2 e uma estrategia efetiva para aumentar o rendimento de graos sob alto nivel de manejo em semeadura precoce (agosto).

Dinâmica do afilhamento afetada pela disponibilidade de nitrogênio e sua influência na produção de espigas e grãos em trigo

Wheat tiller number and survival and ear and grain production as affected by nitrogen supply were studied in cv.Embrapa 16 in three field experiments at Estacao Experimental Agronomica (UFRGS), in Eldorado do Sul, RS, during 1995, 1997 and 1998.The first-year treatment consisted in applying 40kgha-1 of N in different plant stages (emergence to 5th leaf stage), followed or not by an extra N-supply at the 7th leaf stage. In 1997 and 1998, different N rates were applied at plant emergence, followed or not by an extra N-supply at the 7th leaf stage.Nitrogen applied early in the vegetative period stimulated tiller emission while N applied at the 7th leaf stage reduced tiller mortality and maintained synchrony between the main stem and tiller development.Consequently, ear number was increased, leading to a yield boost.

Validação de modelo para predição do potencial produtivo de trigo com sensor óptico ativo

The objective of this work was to validate a model based on the normalized difference vegetation index (NDVI) for the prediction of spatial variability of accumulated biomass in shoots and wheat grain yield. Georeferenced readings of NDVI and biomass, at the end of tillering, and of grain yield were carried out. The proposed method allowed relating classes of spatial variability of NDVI and biomass, with 81% of correspondence between them. However, the relation between spatial variability of yield and NDVI was lower, with 48% of correspondence.

Grazing management in an integrated crop-livestock system: soybean development and grain yield.

Grazing livestock in integrated crop-livestock systems can cause impacts in the subsequent crop cycle. Aiming to investigate how grazing could affect soybean, the 9th crop cycle of a pasture/soybean rotation was assessed. Treatments were grazing intensities (10, 20, 30 and 40 cm of sward height) applied since 2001 in a mixed of oat and annual ryegrass; and an additional no grazing area as control. Treatments were arranged in a completely randomized block design with three replicates. Grazing affected soybean population and the mass of individual nodules (P 0.05). Soybean yield showed differences among treatments, but no difference was found between grazed and non-grazed areas. Grazing intensities impact the coverage and frequency of weeds (P>0.05). In conclusion, grazing intensity impacts different parameters of soybean yield and development, but only the grazing intensity of 10 cm can jeopardize the succeeding soybean crop.

Regulation of nitrogen absortion and assimilation in plants

A presente revisao tem por objetivo discutir os mecanismos de regulacao da absorcao e assimilacao do nitrogenio nas plantas, de modo que a eficiencia de uso desse nutriente seja aumentada. O nitrogenio e absorvido nas raizes sob a forma de NO3 ou NH4 , sendo entao incorporado em aminoacidos na propria raiz ou na parte aerea. A taxa e a quantidade de nitrogenio absorvido e assimilado durante o ciclo da planta dependem da presenca de carregadores especificos na membrana plasmatica, da atividade das enzimas envolvidas no seu ciclo, da disponibilidade de energia necessaria para os processos de absorcao e assimilacao e do estadio de desenvolvimento da planta. Inumeros grupos de pesquisa tem centrado esforcos na identificacao dos pontos mais limitantes do metabolismo do nitrogenio nas plantas. Os limitadores tem sido relacionados com: a) a afinidade dos carregadores pelo nitrato e amonio; b) o suprimento de carboidratos as raizes; c) o nivel de aminoacidos no floema radicular; d) a atividade das enzimas redutase do nitrato (RN), sintetase da glutamina (GS) e sintase do glutamato (GOGAT); e) a fonte de N suprida as plantas (NO3 ou NH4 ); f) o local de assimilacao do N (raiz ou parte aerea). Esses estudos tem mostrado que o metabolismo do N e multiregulado e integrado ao metabolismo geral da planta. A identificacao de pontos metabolicos especificos que sao mais limitantes para o incremento da produtividade e complexa. A perspectiva e que a clonagem dos transportadores de N podera auxiliar os programas de melhoramento genetico na obtencao de plantas mais eficientes na absorcao do nitrogenio.