Humic acids (HAs) have a major effect on nutrient uptake, metabolism, growth and development in plants. Here, we evaluated the effect of HA pretreatment applied with a nutrient solution on the uptake kinetics of nitrate nitrogen (N-NO 3 − ) and the metabolism of nitrogen (N) in rice under conditions of high and low NO 3 − supply. In addition, the kinetic parameters of NO 3 − uptake, N metabolites, and nitrate transporters (NRTs) and the plasma membrane (PM) H + -ATPase gene expression were examined. The plants were grown in a growth chamber with modified Hoagland and Arnon solution until 21 days after germination (DAG), and they were then transferred to a solution without N for 48 h and then to another solution without N and with and without the addition of HAs for another 48 h. After this period of N deprivation, the plants received new nutrient solutions containing 0.2 and 2.0 mM N-NO 3 − . Treatment of rice plants with HA promoted the induction of the genes OsNRT2.1-2.2/OsNAR2.1 and some isoforms PM H + -ATPase in roots. The application of HAs differentially modified the parameters of the uptake kinetics of NO 3 − under both concentrations. When grown with 0.2 mM NO 3 − , the plants pretreated with HA had lower K m and C min values as well as a higher V max /K m ratio. When grown with 2 mM NO 3 − , the plants pretreated with HA had a higher V max value, a greater root and shoot mass, and a lower root/shoot ratio. The N fractions were also altered by pretreatment with HA, and a greater accumulation of NO 3 − and N-amino was observed in the roots and shoots, respectively, of plants pretreated with HA. The results suggest that pretreatment with HA modifies root morphology and gene expression of PM H + -ATPases and NO 3 − transporters, resulting in a greater efficiency of NO 3 − acquisition by high-and low-affinity systems.
O girassol (Helianthus annuus L.) tem se destacado como cultura promissora, dentre as oleaginosas com importância agroenergética. Considerando-se os nutrientes exigidos pela cultura do girassol, o nitrogênio é o que mais limita a produção, além de afetar seu rendimento de óleo. Este trabalho objetivou avaliar aspectos do metabolismo e a cinética de absorção de nitrogênio (nítrico e amoniacal) na variedade de girassol BRS 324, cultivada em diferentes concentrações desse nutriente, em solução nutritiva, sob condições controladas, em câmara de crescimento. As plantas receberam 0,2 mmol L-1 e 2,0 mmol L-1 de N-NH4+ ou N-NO3-, em delineamento experimental inteiramente casualizado. Foram avaliados os parâmetros cinéticos de absorção (Km e Vmax), massa fresca, acúmulo de frações solúveis nitrogenadas e açúcares. Plantas cultivadas em 2,0 mmol L-1 de N-NH+ apresentaram maior Vmax, indicando maior capacidade de transporte desse íon. O caule apresentou acúmulo preferencial de NO3- e açúcares solúveis, atuando como principal local de reserva energética da planta. Os tratamentos com NH4+ resultaram em correlações negativas entre a massa fresca e a quantidade desse composto no tecido vegetal, o que pode ser responsável por sintomas de toxidez, resultando em redução na relação raiz/ parte aérea.
Iron is an essential nutrient but is toxic in excess mainly under acidic conditions. Yeasts have emerged as low cost, highly efficient soil inoculants for decontamination of metal-polluted areas, harnessing...
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.
Cinética de absorção e frações nitrogenadas em arroz expressando o fator de transcrição OsDof26
1Absorption kinetics and nitrogen fractions in rice as an expression of the OsDof26 transcription factor
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