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Sunflower (Helianthus annuus L.) has great economic importance due to its oil yield and quality. Among the factors influencing these parameters, nitrogen fertilization stands out. In this study we evaluated the effect of different N-urea doses (0,10,30,50,90,130 kg N-urea ha-1) at planting and 30 days after emergency on soluble fractions, oil profile and yield of three sunflower cultivars (BRS324, Catissol 01and Neon). Plants were harvested at the flowering stage for metabolic study, and at the end of the cycle for oil extraction and characterization. The Catissol 01 genotype presented the highest N-NO3- accumulation capacity, mainly in the stem. The Neon genotype presented the highest achene production at 30 and 50 kg N ha-1. Oleic oil had the highest yield, with the Catissol 01 and Neon cultivar standing out. Among the cultivars, Catissol 01 is economically more suitable for biofuel production, when cultivated at 50 kg N ha-1 since higher N doses did not result in increased oil yield. O girassol é uma espécie com importante valor econômico pela qualidade e rendimento de óleo. Entre os fatores que influenciam esses parâmetros se destaca a fertilização nitrogenada. Este trabalho avaliou o efeito de doses crescentes de N-uréia (0, 10, 30, 50, 90, 130 kg de N-Uréia ha-1 aplicadas no plantio e aos 30 dias após a emergência) sobre as frações solúveis, rendimento e perfil do óleo de três genótipos de girassol (BRS324, Neon e Catissol 01). As plantas foram coletadas no estádio de floração para o estudo metabólico e ao final do ciclo para a extração e caracterização de óleo. O genótipo Catissol 01 apresentou maior capacidade de acúmulo de N-NO3-, preferencialmente no caule. A maior produção de óleo por planta foi observada no BRS324, nas doses entre 30 e 50 kg N ha-1, embora o genótipo Neon tenha apresentado a maior produção de aquênios. O ácido oléico foi o de maior rendimento com destaque para os genótipos Catissol 01 e Neon. Dentre os genótipos avaliados, o Catissol 01 é economicamente mais indicado para a produção de óleo destinada ao biocombustível, quando cultivado com a dose de 50 kg N ha-1, pois doses superiores de N não resultam em aumento na produção de óleo.

Four genetically contrasting rice varieties (IAC-47, Bico Ganga, Arroz de Revenda and Manteiga) according to Random Amplified Polymorphic DNA (RAPD) analysis were assessed regarding expression of the genes OsNRT1.1, OsNRT2.1 and OsNRT2.2 and the nitrate uptake kinetics parameters (Km and Vmax). Up to 250-fold increases in the induction of gene expression after nitrate resupply were observed for the high-affinity transporter (OsNRT2.1 and OsNRT2.2). However, no significant variations in Vmax among the varieties were obtained. The lower value of Km of the IAC-47 cultivar in relation to the Arroz de Revenda variety suggests a greater role of high-affinity transporter genes. These results indicate that closer attention should be paid to the expression levels of these genes in selecting varieties aiming to enhance nitrogen uptake efficiency.

Nitrogen is essential for plant growth and development and directly influences both grain production and oil content. Boron has been studied in sunflower cultivation due to high demand of this culture for this nutrient. This study aimed to evaluate the N and B differential supply effect on the grain and oil production of sunflower plants. The experiment was conducted in a greenhouse and used two sunflower hybrids: BRS 321 and Neon. N and B were applied via nutritive solution according to the following treatments: B + 50 N (2.49 kg ha-1 B and 10 kg ha-1 N at planting and 40 kg ha-1 B as additional fertilization); B + 10 N (2.49 kg ha-1 B and 10 kg ha-1 N at planting); 50 N (0 B and 10 kg ha-1 N at planting and 40 kg ha-1 N as additional fertilization) and 10 N (0 B and 10 kg ha-1 N at planting). Analyses of total N and B in all collected plant parts were performed, as well as measurements of grain production for each chapter and oil extraction at the end of the cycle. The association between B fertilization and a greater amount of N fertilization was essential to BRS 321 oil production. Regarding grain production at lower levels of N fertilization, Neon presented the best response to B application. RESUMO. O nitrogênio é essencial para o crescimento e desenvolvimento das plantas e tem influência direta na produção de grãos e conteúdo de óleo. O boro tem sido bastante estudado no cultivo de girassol, devido a alta exigência desta cultura por este nutriente. Este trabalho teve por objetivo avaliar o efeito de nitrogênio e boro na produção de grãos e óleo em plantas de girassol. O experimento foi conduzido em casa de vegetação utilizando-se dois híbridos: BRS 321 e Neon. N e B foram aplicados em solução nutritiva: B + 50 N (2,49 kg de B ha-1 e 10 kg de N ha-1 no plantio e 40 kg de N ha-1 suplementar); B + 10 N (2,49 kg de B ha-1 e 10 kg de N ha-1 no plantio); 50 N (sem B e 10 kg de N ha-1 no plantio e 40 kg de N ha-1 suplementar); 10 N (sem B e 10 kg de N ha-1 no plantio). Ao final do ciclo foi analisado os teores de N e B total em todas as partes das plantas, produção de grãos por capítulo e teor de óleo. A combinação entre o fornecimento de B com a maior adubação nitrogenada foi essencial para a produção de óleo pelo híbrido BRS 321. Em relação à produção de grãos com menor adubação nitrogenada Neon apresentou a melhor resposta à aplicação B.

Duas cultivares de arroz, Piauí (tradicional) e IAC-47 (melhorada), foram colocadas em solução nutritiva contendo 20 mg de N-NO3- L-1 até 32 dias após a germinação (DAG). Depois disso, um grupo de plantas passou a receber 200 mg de N-NO3- L-1, enquanto o outro continuou recebendo 20 mg de N-NO3- L-1 até os 42 DAG. De 42 até os 56 DAG, todas as plantas receberam 5 mg de N-NO3- L-1 até o fim do ciclo. Esses tratamentos foram empregados visando simular o fluxo sazonal de nitrato existente nos solos de regiões tropicais. As plantas foram coletadas aos 133 DAG e separadas em folha bandeira, folha 2, colmos e raízes. Foram determinados os teores de N na forma de aminoácidos, nitrato e amônio, açúcares solúveis, atividades da nitrato redutase (NR) e glutamina sintetase (GS). O fluxo sazonal de nitrato influenciou significativamente a absorção e o uso de N. As variedades estudadas foram responsivas de maneira diferenciada em relação ao acúmulo e à translocação de N, quando submetidas ao fluxo sazonal de nitrato. A cultivar Piauí parece acumular mais NO3- em seus tecidos na fase inicial do seu ciclo, podendo permitir sua posterior translocação. A folha bandeira e folha 2 parecem atuar como local preferencial de acúmulo de N, sendo este acúmulo mais intenso na cultivar Piauí. Two rice cultivars, Piaui (a landrace) and IAC-47 (an improved variety), were grown in nutrient solution containing 20 mg nitrate (N-NO3-) L-1 up to 32 days after germination (DAG). After this, a group of plants received 200 mg N-NO3- L-1, while the other was kept at 20 mg N-NO3- L-1 up to 42 DAG. From 42 until 56 DAG, all plants received 5 mg N-NO3- L-1 until the end of the cycle. These treatments were applied with the objective to simulate nitrate flush in tropical regions. Plants were collected at 133 DAG and separated in to leaf flag, leaf 2, stem and roots. N contents in amino acids, nitrate and ammonium forms, soluble sugars, nitrate reductase (NR) and glutamine synthetase (GS) enzymatic activities were determined. The evaluated varieties replay in different manner about accumulate and translocation nitrate. The variety Piaui seems to accumulate more NO3- in the tissues at the initial phases of its cycle, allowing subsequent remobilization. Flag leaf and leaf 2 seem to act as preferential sites of N accumulation, being this accumulation more intense in the landrace variety.

Two rice varieties, ‘Piaui’ (a landrace) and ‘IAC-47’ (an improved variety), were grown in nutrient solution containing 20 mg nitrate (NO3 −)-nitrogen (N) L− 1 up to 32 days after germination (DAG). After this, a group of plants received 200 mg NO3 −NL− 1, while the other was kept at 20 mg NO3 −NL− 1 up to 42 DAG. From 42 until 56 DAG, all plants received 5 mg NO3 −NL− 1. Plants were collected at 42 and 56 DAG, soluble fractions, nitrate reductase (NR) and GS enzymatic activities were determined. The nutritional history of the plants affected significantly the uptake and use of nitrogen (N), and should be taken into consideration in the studies of N-use efficiency. The variety ‘Piaui’ was more efficient than ‘IAC-47’ in N-uptake use, accumulating more NO3 − in its tissues at the initial phases of its cycle for subsequent utilization.

Hairy roots can be used for metabolic studies and also as a substrate for arbuscular mycorrhizal fungi (AMF). However, little is known about the behavior of these roots when infected with AMF. The metabolism of hairy roots grown with or without AMF, on two culture media, was investigated. An increase in protease activity was observed when the roots were cultured on medium with high nitrogen (N)-content. Glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) activities increased along the development in both carrot and clover hairy roots. With the advancement of root senescence (at 132 d) a greater degradation of root tissue occurred, which was characterized by an increase in catabolic enzymes activity (proteases and GDH deamination). The results indicate that the glutamine synthetase/GOGAT pathway, characteristic of plant tissues, ceases to act in synchronism and is replaced by the GDH/GOGAT system under conditions of stress or senescence when excess ammonium is present.

An upland rice variety IAC‐47 was grown in a greenhouse to determine the effect of foliar nitrogen (N) supplementation during grain development on the activity of the N assimilation enzymes, nitrate reductase (NR) and glutamine synthetase (GS), on free amino‐N content and leaf soluble sugars, and on grain crude protein content. At 10 and 20 days after anthesis (DAA), the leaves were fertilized with a liquid fertilizer containing 32% N as 12.8% urea, 9.6% ammonium (NH4), and 9.6% nitrate (NO3) in increasing rates corresponding to 0,20+20, 40+40, and 60+60 kg N ha‐1. Leaves were collected twice (at 12 DAA and 14 DAA for GS activity, sugar and amino‐N content, and at 11 and 13 DAA for NRA) after each application of leaf N. The late foliar application of N increased significantly grain crude protein without a corresponding decrease in grain weight. The NR activity (NRA) increased after the foliar application of N. In the flag leaf, 60+60 kg N ha‐1 (21 DAA) resulted in higher NRA (20x over the control...

Grain yield and grain protein levels are usually negatively correlated. However, when the appropriate timing for nitrogen (N) supplementation is used, a significant increase in rice grain protein can be obtained without a corresponding decrease in grain yield. Increased N doses, equivalent to 40, 80, and 120 kg N ha‐1, applied at 10 and 20 days after anthesis (DAA), led to 13, 27, and 18% increases in grain crude protein, respectively, compared to the control. The shoot weight of plants receiving foliar spray of N, did not differ significantly from that of untreated check plants, indicating that the extra N was utilized for other processes. The highest crude protein level (86.2 mg g‐1) was obtained at 40+40 kg N ha‐1, whereas the crude protein content, resulting from the highest N dose (60+60 kg ha‐1), was only 80.0 mg g‐1. Glutelin was the fraction that most contributed to the increase in grain protein content. A positive correlation between crude protein and glutelin level (r=+0.92**) indicated...

A study was conducted on the effect of supplemental nitrogen (N) (20 hg/ha) applied as a foliar spray or to the soil on seed production, protein percentage, and protein fractions of rice. Plants were grown in a greenhouse over two different periods of time, i.e., August 1988 to January 1989 (Period I), and December 1988 to April 1989 (Period II). Nitrogen was applied to the leaves 10 and 20 days after anthesis (DAA), and to the soil at anthesis and at 15 DAA. Average temperature was 28.7°C during Period I and 32°C during Period II, corresponding to 18.7 and 22.0 growing degree‐day/day (GDD/day), respectively. The difference in GDD/day reduced the plant cycle from 130 days during Period I to 109 days during Period II. Plants grown during Period II had larger numbers of spikelets, a higher percentage of “full grown grains”;, and higher grain weight. Although percentage crude protein was about the same for the two periods, prolamin content was increased and the albumin+globulin fraction was decrease...