Assimilação metabólica de nitrogênio em plântulas de seringueira cultivadas com nitrato ou amônio

Abstract

Resumo -O objetivo deste trabalho foi avaliar a assimilação metabólica de nitrogênio em plântulas de seringueira cultivadas na presença de nitrato ou de amônio, por meio da quantificação da atividade das enzimas redutase do nitrato (RN), glutamina sintetase (GS), glutamato sintase (GOGAT) e glutamato desidrogenase (GDH). Os seguintes tratamentos foram avaliados: fontes de N -controle, sem aplicação de N; amônio a 8 mmol L -1 ; e nitrato a 8 mmol L -1 -e tempos de exposição -0 e 27 dias -, em arranjo fatorial 3x2, no delineamento inteiramente casualizado, com quatro repetições. A forma amoniacal promoveu maior assimilação metabólica de N, o que resultou em maior acúmulo de aminoácidos. A assimilação, tanto da forma nítrica quanto da amoniacal, aconteceu principalmente via GS/GOGAT; parte do N nítrico é assimilado nas raízes, com pequena participação da GDH, e parte é translocada para outros órgãos. O N amoniacal é totalmente assimilado nas raízes, com significativa participação da GDH. Nas folhas, a GS participa tanto da assimilação primária como da reassimilação do amônio fotorrespirado, independentemente da fonte nitrogenada, enquanto a enzima GDH tem papel secundário, independentemente da fonte ou do tempo de exposição. A atividade da RN in vitro é detectada somente em raízes e caules.Termos para indexação: Hevea brasiliensis, amônio, atividade enzimática, fonte de nitrogênio, metabolismo, nitrato. Metabolic assimilation of nitrogen in rubber tree seedlings grown with nitrate or ammoniumAbstract -The objective of this work was to evaluate metabolic assimilation of nitrogen in rubber tree seedlings grown with nitrate or ammonium, by quantifying the activity of the enzymes nitrogen reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH). The following treatments were evaluated: nitrogen sources -control, without N application; 8 mmol L -1 ammonium; and 8 mmol L -1 nitrate -, and exposure times -0 and 27 days -, in a 3x2 factorial arrangement, in a completely randomized block design with four replicates. The ammoniacal form favored higher N metabolic assimilation, which lead to a higher aminoacid accumulation. Both nitrate and ammonium assimilations occurred mainly by GS/GOGAT route; part of the nitric nitrogen is assimilated in the roots, with little GDH participation, and the other part is translocated to other organs. Ammonium nitrogen is totally assimilated in roots, with a significant participation of GDH. In the leaves, GS participates in the primary assimilation, as well as in the photorespiratory ammonium re-assimilation, irrespective of the N source, while GDH has a secondary role, independently of the source or of the exposure time. In vitro RN activity is detected only in the roots and stems.

Changes induced by co-inoculation in nitrogen–carbon metabolism in cowpea under salinity stress

“…There are two possible metabolic pathways for the incorporation of ammonium ions to form amino acids: the first involves the enzymes glutamate dehydrogenase (GDH) and glutamine synthetase (GS), and the second involves glutamine synthetase (GS) and glutamate synthase (GOGAT). 43 The present study demonstrated that some co-inoculations are more efficient at maintaining GS activity under salt stress, indicating that those plants have a greater capacity to incorporate ammonium under saline conditions corresponding to an EC of 5.6 mS cm −1 . The results show that co-inoculations elicit different metabolic pathways for the formation of amino acids; some plants prioritize the GS/GOGAT metabolic pathway for the incorporation of ammonium, while other co-inoculations elicit the alternative pathway GDH/GS of nitrogen assimilation.…”

EFFECT OF SOIL COMPACTION AND CO-INOCULATION WITH Azospirillum brasilense ON THE DEVELOPMENT OF PEANUT PLANTS

“…Higher value of plant height in noncompacted soil than in compacted soil is due to the fact that compaction reduces macroporosity and affects the amount of oxygen in the soil (TREVISAN et al, 2017). Thus, the oxidation of ammonium to nitrate, which corresponds to the form of greatest absorption by plants, is compromised (SHAN et al, 2012). In addition, under anoxic conditions there are losses of nitrate due to denitrification (CHANG et al, 2011).…”

Chlorophyll, nitrogen and antioxidant activities in Cumaru (Dipteryx odorata (Aubl.) Willd) (Fabaceae) in two water regimes

“…The ammonium and the nitrate are the main forms of nitrogen available to plants, reduction processes and nitrogen assimilation can be absorbed both in the leaves and in the roots simultaneously or between these bodies becoming an essential process for the plant, since it is through it that It is controlled growth and development of the plant (Shan et al, 2012).…”