Molecular Frameworks of Nitrogen Response in Plants: A Review

Nitrogen is a crucial element for all living organisms especially plants which rely on substantial nitrogen quantities to sustain their growth and productivity. Crop production is greatly influenced by nitrogen consumption efficiency and a significant amount of nitrogen fertilizers is used to increase yield. Approximately half of N fertilizers are not utilized by the crops and are lost to the environment by polluting water sources or by releasing pollutants into the atmosphere. From the rhizosphere, plants absorb nitrogen in the form of nitrate (NO3-), ammonium (NH4+), or organic nitrogen (amino acids and urea). Plants exhibit an array of sensing and adaptive mechanisms to respond to the diverse nitrogen nutrition conditions which include morphological and physiological responses. Two primary systems govern nitrogen uptake in plants: the High-affinity transport system (HATS) and the Low-affinity transport system (LATS). Nitrate transporters fall into two categories, Nitrate Transporter 1 (NRT1) and Nitrate Transporter 2 (NRT2) transporters, Chloride Channel Family (CLC) transporters and Slow Anion Associated Channel Homologs (SLAC/SLAHs). The ammonium transporter family includes Ammonium Transporter 1 (AMT1) and Ammonium Transporter 2 (AMT2) transporters. The uptake of organic nitrogen is facilitated through amino acid and urea uptake and transport systems. In fluctuating environmental conditions, plants employ nitrogen response mechanisms to fine-tune homeostasis. A comprehensive understanding of these regulatory mechanisms holds the potential to yield valuable insights for the development of crops with enhanced nitrogen use efficiency.

A critical review on: Significance of floral homeotic APETALA2 gene in plant system

Flower development is a complex procedure regulated by combinatorial factors, such as transcription factors,peptides, hormones, and small RNAs. One of the important gene determining the floral structure and floral meristem isAPETALA2 (AP2) which belongs to a large family of transcription factors. AP2 contributes stochastically in signalingpathway in flower development and in various bioactive components synthesis. The presence of GbAP2 transcriptsin live fossil Ginkgo biloba leaves and female strobili tissue showed that GbAP2 might be involved directly in leafand female strobili development, whereas it may possible that GbAP2 indirectly involved in synthesis of bioactivecompounds such as flavonoids, terpenoids, ginkgolides, and organic acids. Gingko or Ginkgo biloba is among themost popular plant used in United States. Bioactive compounds isolated from the ginkgo plant are thought to exhibitas antioxidant and antiplatelet activity. Due to the pleotropic nature of AP2, it is involved in various tissues such asregulating in floral pattern, stem cell maintenance, floral organ identity, floral meristem, leaves, development of stems,and seed development. AP2 also regulate number of downstream genes but its own expression is negatively regulatedat translational or post-translational levels by miRNA172 which is a small RNA (22 bp) and binds to complementaryregion of AP2 transcript. Mutation in AP2 showed increases in seed size and seed mass, this property of AP2 could beused in medicinal plant to enhance the valuable product. Since AP2 is engaged in various pathways it is essential tocompile the functioning in the form of presented manuscript, which discusses the structure and functioning of AP2.We likewise explain how AP2 involved in various expressions and its regulatory mechanism, especially in the plant.

Phenotypic stability and homeostasis in Assam rice landraces at varying nitrogen regimes

Aim: The present study was designed to identify stable rice (Oryza sativa L.) genotypes for nitrogen use efficiency (NUE), yield and its component traits and also to identify component traits associated with yield stability. Methodology: Twenty-one landraces along with five high yielding varieties (HYVs) of rice were evaluated at three nitrogen levels (0, 40 and 60 kg N ha-1) for two years (2014 and 2015). Eberhart and Russel’s (1966) stability analysis were employed to assess the genotype × environment (GE) interaction and the stability of the genotypes across six environments. To study homeostasis, simple correlation analysis among ten different traits was done based on stability parameters. Results: The present study revealed that environments created by graded nitrogen levels were fruitful for inducing environmental variations. The highly significant linear environmental variances were found for all ten traits. Linear GE interaction was significant for all the traits, except harvest index, grain nitrogen and nitrogen harvest index. The stability analysis identified four genotypes viz., Kolabor, Aki Bora, Rongdoi and Luha Sali with average stability whereas Betguti Sali was found to be stable below average. Correlation analysis based on stability parameters revealed the existence of homeostasis. Interpretation: Present study revealed that genotypes namely Kolabor, Aki Bora, Rongdoi and Luha Sali are suitable to grow under both nitrogen limiting and nitrogen non-limiting environments whereas Betguti Sali was suitable for nitrogen non-limiting environments. Correlation analysis, based on stability parameters, revealed that yield stability was due to the plasticity of some other component traits under study.

Palisadegrass effects on N fertilizer dynamic in intercropping systems with corn

ABSTRACT Corn grain yield, nitrogen (N) fertilizer efficiency and distribution to corn alone and three forms of corn and palisadegrass (Urochloa spp.) intercropping implantation was investigated. A field experiment with 15N labeling fertilizer was performed in randomized block design. No form of palisadegrass intercropping implantation affected corn grain yield, total N accumulation and N use efficiency (NUE), which were 8.7 t ha-1, 205 kg ha-1 and 37% respectively. The palisadegrass produced on average 1.9 t of dry mass, absorbing a maximum of 6 kg ha-1 or 5.5% of N fertilizer during corn growing. Furthermore, the palisadegrass did not affect N fertilizer distribution in soil-plant system, in which 28.2% was recovered in the soil and 40.4% in the plants (corn + palisadegrass). The results show that for the three intercropping implantation methods the palisadegrass did not compete with corn for N fertilizer.

Production and chemical composition of hybrid Brachiaria cv. Mulato II under a system of cuts and nitrogen fertilization / Produção e composição bromatológica da Brachiaria híbrida cv. Mulato II sob regime de cortes e adubação nitrogenada

The production capacity of green and dry mass of the entire plant, efficiency of N conversion, apparent N recovery and the chemical composition of cultivar Mulato II was evaluated under a system of cuts and nitrogen doses. The assay, conducted in the municipality of Goiânia, GO, Brazil, had a totally randomized 2 x 4 factorial design (2 height cuts, 0.40 and 0.50 m and 4 nitrogen doses), with three replications and subdivided subplots. Treatments comprised four N doses (0, 50, 100 and 150 kgha-1 N, with urea as nitrogen source). There was no significant interaction (p>0.05) between N doses and cut heights for the variables productivity of green (PGM) and dry (PDM) mass, nitrogen use efficiency (NUE) and apparent N recovery (ANR), which were neither affected (p<0.05) by N doses nor by evaluated cut heights. Average productivity reached 59,450 kgha-1 (PGV) and 10,367 kgha-1 (PDM) and it was produced an average of 19.62 kg of DM per kg of N, with a mean 56.00% recovery. N doses and cut heights did not affect (p>0.05) DM rates of the plant, whilst mean dry matter rate was 17.49%. CP rates were affected (p<0.05) by N doses (0, 50, 100 and 150 kgha-1) and cut heights (0.40 and 0.50 m) and by the interaction of these factors. CP rates of the entire plant hybrid Brachiaria cv. Mulato II increased (p<0.05) due to N doses through an increasing linear relationship. Since there was a significant effect (p<0.05) with regard to cut height and CP rates decreased with height increase. NDF rates were significantly influenced by N doses (p<0.05) and by cut heights (p<0.05), with significance for the interaction (p<0.05) of over 100 kgha-1 N doses only. No significant interaction (p>0.05) occurred in ADF rates among the variables analyzed. ADF contents were influenced by N supply (p<0.05) with decreasing quadratic regression as N doses increased.

O presente trabalho de pesquisa teve como objetivo avaliar o potencial produtivo de massa verde e seca da planta inteira, a eficiência de conversão do N, a recuperação aparente do N, bem como a composição bromatológica do cultivar Mulato II, sob regime de cortes e submetido a doses de nitrogênio, no município de Goiânia, GO, Brasil. Utilizou-se um delineamento experimental inteiramente casualizado com arranjo fatorial 2 X 4 (2 alturas de corte (0,40 e 0,50 m) X 4 doses de nitrogênio) com três repetições e parcelas subdivididas. Os tratamentos foram constituídos por quatro doses de N (0, 50, 100 e 150 kgha-1 de N) (sendo a fonte ureia). Não ocorreu interação significativa (p>0,05) entre doses de N e alturas de corte para as variáveis produtividades de massa verde (PMV) e massa seca (PMS), eficiência de conversão aparente de nitrogênio (ECAN) e recuperação aparente de nitrogênio (RAN), que não foram influenciadas (p<0,05) pelas doses de N, nem em função das alturas de corte avaliadas. A média de produtividade encontrada foi de 59.450 kgha-1 (PMV) e 10.367 kgha-1 (PMS), produzindo em média 19,62 kg de MS para cada kg de N aplicado, com uma recuperação média de 56,00%. As doses de N aplicadas e as alturas de corte não influenciaram (p>0,05) os teores de MS da planta. A média do teor de matéria seca encontrada foi de 17,49%. Os teores de PB foram influenciados (p<0,05) pelas doses de N (0, 50, 100 e 150 kgha-1) e alturas de corte (0,40 e 0,50 m) bem como a interação desses fatores. Os teores de proteína bruta (PB) da planta inteira Brachiaria híbrida cv. Mulato II aumentaram (p<0,05) em função das doses de N, apresentando uma relação linear crescente. Quanto à altura de corte, ocorreu também efeito significativo (p<0,05), evidenciando que os teores de PB diminuíram com o aumento da altura. Os teores de FDN foram influenciados significativamente pelas doses de N (p<0,05) e pelas alturas de corte (p<0,05), apresentando significância para a interação (p<0,05) apenas nas doses acima de 100 kgha-1 de N. Para os teores de FDA não houve interação significativa (p>0,05) entre as variáveis analisadas. O conteúdo de FDA foi influenciado pelo fornecimento de N (p<0,05), apresentando regressão quadrática decrescente com o aumento das doses de N.

Heterobeltiosis in Wheat (Triticum aestivum L.) F1 Diallel Crosses under Contrasting Soil-N Conditions.

Breeding wheat cultivars with improved adaptation to low soil-N, has gained importance worldwide in order to decrease N fertilizer consumption and overcome the ecological and economic problems of the misuse of this fertilizer. Identification of wheat crosses that show useful heterosis (heterobeltiosis) is an important issue in breeding programs. The main objective of the present investigation was to estimate heterobeltiosis for nitrogen use efficiency and other studied traits of F1 diallel crosses among six wheat parents in order to identify the superior ones for future use in breeding programs. Genetic materials were evaluated at two seasons (2007/2008 and 2008/2009) in a split-plot design with randomized complete block arrangement, using three replications. Main plots were assigned to N levels (0 and 75 kg N/fed), while sub plots were devoted to genotypes. Data combined across the two seasons were presented. In general, low N caused a significant reduction in 9 out of 14 studied traits. These reductions were relatively high in magnitude for number of spikes/ plant (SPP) for parents (23.65%) and F1's (23.99%). On the contrary, low–N caused increases in the averages of nitrogen use efficiency (NUE) by 89.5 and 97.60% for parents and F1's, respectively. Averages of heterobeltiosis for all studied characters were either nonsignificant or significant but non favorable, except for plant height under both low and high N, NUPE under high N and GPS under low N. However, some crosses for each trait showed significant and favorable heterobeltiosis. Under low–N, the highest favorable and significant heterobeltiosis estimate was shown by L27 x Gem 7 for GYPP (14.94%), NUTE (44.81%) and GPS (25.82%), L25 x L26 for 100 GW (13.87%), L 25 x L 27 for SPP (12.53%), L 27 x Gem 9 for GPS (26.19%) and Gem 7 x Gem 9 for BYPP (28.99%).

Natural selection for efficiency in the use of nitrogen in common bean identified by analysis of microsatellites and grain yield

This study was carried out in order to verify whether natural selection acts on segregating common bean populations grown in the presence and absence of N, and to verify that natural selection affects the frequency of microsatellite alleles specifically, and in order to identify those that can assist in selection. Four populations from the crosses Ouro Negro x CI-107 and VC-5 x IAPAR-81 were carried forward in bulk to F8 at both levels of N. Ouro Negro and VC-5 are considered stress tolerant to nitrogen and IAPAR-81 and CI-107 responsive. One hundred progenies were obtained from each cross and grown in the presence and absence of N. DNA was extracted from 400 progenies, of which 194 were evaluated in the rainy season and 79 in the winter crop for grain yield. These progenies were evaluated in two separate experiments with and without N, in a 14 x 14 lattice design during rainy season and 9 x 9 in the winter season. We selected 35 pairs of polymorphic primers from the parents, with 20 being common from the two crosses. Using DNA of the 400 progenies, it was found that natural selection acted in 33 loci, in at least one environment and cross, and that alleles of the four parents were favoured by natural selection. QTLs were identified for the response rate of N and for grain yield and the linked markers are potential for assisted selection, especially the two most stable; BMD-20, in response to the use of N and PVBR-93 for grain yield.

Eficiência nutricional e aproveitamento do nitrogênio pelo capim-marandu de pastagem em estágio moderado de degradação sob doses e fontes de nitrogênio / Nutritional efficiency and nitrogen uptake by capim-marandu at pasture in moderate stage of degradation under doses and sources of nitrogen

O presente estudo foi desenvolvido sob condições de campo, visando avaliar a eficiência no uso e no aproveitamento do nitrogênio pelo capim-marandu por meio de diversos índices. O experimento foi conduzido na Fazenda Modelo da Universidade Estadual de Goiás (UEG) num Latossolo Vermelho distrófico, no período de julho de 2003 a março de 2006. O delineamento experimental utilizado foi de blocos ao acaso, com três repetições. Os tratamentos nas parcelas foram caracterizados por um fatorial 2 x 4, sendo duas fontes de N (sulfato de amônio e uréia) e quatro doses de N (0, 100, 200 e 300 kg/ha). Na subparcela, os tratamentos foram representados pelos anos (2004, 2005 e 2006), referentes ao tempo de recuperação da pastagem. A adubação nitrogenada foi parcelada em três aplicações após cada corte de avaliação da forrageira. Foram realizados três cortes da forrageira por ano, avaliando-se a massa seca e os teores de N nos tecidos. Com esses resultados, avaliaram-se os índices de Eficiência de Utilização do N (EUN), Recuperação do N Aplicado (RNA), Eficiência Agronômica do N Aplicado (EA) e Eficiência Fisiológica (EF) ou Eficiência Biológica. Os resultados mostraram que a EUN aumentou, enquanto que a RNA, EA e a EF diminuíram com o aumento das doses de N aplicadas. Em todos os casos, os índices foram influenciados pelos anos de recuperação da forrageira estudados, mas não pelas fontes de N.

This study was accomplished under field conditions, to evaluate the use and efficiency of nitrogen uptake, through various indexes, in pasture of Brachiaria brizantha. The experiment was conduced at the Model Farm of the Goiás State University in a distrophic Dark Red Latosol, from 2003 July to 2006 March. The experimental design was randon blocks, with three replicates. The treatments were placed in parcels characterized by a 2x4 factorial, with two sources of N (ammonium sulfate and urea) and four doses of N (0, 100, 200 and 300 kg/ha/year). In sub - parcel, the treatments were represented per years (2004, 2005 and 2006) refering to time of pasture recovery. The use of nitrogen was divided in three times, after each cut evaluation of the forage pasture. Three cuts were made per year, evaluating dry mass and N accumulation in the tissue. Nitrogen Utilization Efficiency, Recovery from the N Applied, Agronomic Efficiency from the N Applied, Physiological or Biological Efficiency indexes were evaluated. The results showed that EUN increased, while RNA, EA and EF reduced with the increase in the N doses applied. In all cases, the indexes were influenced by the years of recovery the herbage, and not by the sources of N.

Parcelamento da adubação nitrogenada na cultura do milho e utilização do N residual pela sucessão aveia preta-milho / Nitrogen fertilization splitting in maize and residual N utilization for the-black oats-maize succession

Com o objetivo de avaliar a eficiência de utilização do N pela cultura de milho (Zea mays L.), usando-se fertilizante marcado com 15N, aplicado parceladamente (duas formas), e o efeito residual deste fertilizante nas duas culturas subseqüentes em sucessão (aveia preta e milho), sob implantação do sistema plantio direto, foi conduzido um experimento, no sudeste do Brasil, nos anos agrícolas 2003/2004 e 2004/2005, sob um solo de textura areno-argilosa (Hapludox). Os tratamentos consistiram da dose de 120kg ha-1 de N, na forma de sulfato de amônio marcado (15N) e dois parcelamentos de N 30-90 e 60-60kg ha-1. Nas plantas de milho e aveia preta, avaliaram-se o N total acumulado, o N proveniente do fertilizante e a recuperação de N-fertilizante. O incremento da dose de fertilizante nitrogenado aplicado na semeadura (60kg ha-1 de N), no ano agrícola 2003/2004, proporcionou aumento no aproveitamento de N pela planta (65 por cento) em relação ao tratamento que recebeu 30kg ha-1 de N na semeadura (45 por cento).

The objective of this research was to evaluate: a)the N use efficiency by a maize (Zea mays L.) crop, using 15N labeled fertilizer applied in two splittings, and b) the residual effect of this fertilizer in two subsequent crops in succession (black oats and maize), under the introduction of the no tillage system. The experiment was carried out in Southest Brazil, in the cropping seasons 2003/2004 and 2004/2005, under a sandy-clayey loam soil (Hapludox) The first maize crop was in 2003/2004, the second one in 2004/2005 and the black oats crop in between. Treatments consisted of two ways of application of two N splittings (30-90 and 60-60kg ha-1) as 15N labeled ammonium sulphate fertilizer. In the maize and black oat plants, the following were evaluated: accumulated total N, nitrogen in plant derived from fertilizer and N fertilizer recovery. The treatment with 60kg ha-1 of N applied at sowing, in the 2003/2004 crop, increased the plant N use (65 percent) in relation to the treatment that received 30kg ha-1 of N at sowing (45 percent).

Eficiência bioeconômica da adubação de pastagem natural no sul do Brasil / Bioeconomic efficiency of native pasture fertilization in southern Brazilian

O objetivo deste trabalho foi avaliar as produções vegetal e animal e a resposta econômica de uma pastagem natural submetida à adubação de correção e doses de nitrogênio durante a estação de crescimento 1998/99. O experimento foi conduzido em área da Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul (EEA - UFRGS). Em 1996 foram aplicados 3000kg ha-1 de calcário e adubação correspondente a 500kg ha-1 da fórmula 5-20-20. Na análise econômica, considerou-se um terço destas quantidades como referente à utilização na estação de crescimento 1998/99. Os tratamentos foram doses de nitrogênio (N) na forma de uréia (zero, 100 e 200kg ha-1 de N), em um delineamento de blocos ao acaso com duas repetições de área por tratamento. Os animais experimentais foram novilhas de corte com um ano de idade e peso médio inicial de 160kg. A massa de forragem, a taxa de acúmulo diário de matéria seca, a produção total de matéria seca verde e a eficiência de transformação do N em produção primária foram maiores (P<0,1) quanto maior foi a dose de N aplicado. As aplicações de 100 e 200kg ha-1 de N elevaram os custos em 104,1 e 208,2 por cento, respectivamente. A aplicação de 200kg ha-1 de N em pastagem natural apresentou maior produção de peso vivo, margem bruta e eficiência de conversão do N em produto animal. Quando foram utilizados apenas o calcário e a adubação N-P-K de correção, obteve-se o maior retorno financeiro direto. A pastagem natural mostrou resposta positiva à aplicação de fertilizantes, dentro da amplitude de quantidade destes insumos aplicadas no presente trabalho.

This research was aimed at evaluating the plant and animal production and the economic response of a native pasture submitted to the application of N-P-K and nitrogen levels during the 1998/99 growing season. The experiment was conducted at Estação Experimental Agronômica of the Universidade Federal do Rio Grande do Sul (EEA - UFRGS). The pasture was fertilized in 1996 using 3000kg ha-1 of lime and 500kg ha-1 of 5-20-20. The one third of these amounts was considered as that concerning the 1998/99 growing season, in the economic analysis. The treatments were nitrogen (N) levels (zero, 100 and 200kg ha-1 of N) as urea, in a randomized block design with two plots by treatment. The experimental animals were beef heifers with initial age of 1,5 year-old and average live weight of 160kg. The forage mass, dry matter accumulation rate, green dry matter total production and the N transformation efficiency in primary production were enhanced by the N level applied (P< 0.1). The treatments 100 and 200kg ha-1 of N increased the costs in 104.1 and 208.2 percent, respectively. The treatment 200kg ha-1 of N presented the greater area live weight gain, the gross margin and the N conversion efficiency in animal product. The greater net financial return was reached when only lime and N-P-K fertilization were applied. The native pasture showed a positive response to the fertilizer application, within the amplitude of amount of the input applied in this experiment.