Soluble fractions and kinetics parameters of nitrate and ammonium uptake in sunflower ("Neon" Hybrid)

Abstract

-Sunflower plants are source of oilseeds with great importance for agroenergy. Nitrogen deficiency is considered one of the factors limiting growth and yield. The objective of this study was to assess the nitrogen uptake (high and low supply of nitrate and ammonium) and to determine the uptake kinetics parameters (K m and V max ) of these ions in sunflower plants (Neon hybrid). The experiment was carried out in a growth chamber using a hydroponic system. The following treatments were applied: 0.2 and 2.0 mmol L -1 of N-NO 3 -and N-NH 4 + . The two kinetics parameters (K m and V max ) involved in the uptake of nitrate and ammonium were determined, as well as the soluble fractions (N-NO 3 -, N-NH 4 + , amino-N and sugars) and total N, in different plant tissues. The plants grown with ammonium showed higher V max than those cultivated with nitrate. High ammonium rates caused reduction of root volume and the plants supplied with 2.0 mmol L -1 of N-NO 3 -produced more biomass from the roots and aerial part. The highest concentrations of N-NO 3 -were found in the petioles. Analyzed together, the data suggest a greater potential for use of nitric-N as a nitrogen source for fertilization in the cultivation of sunflower. RESUMO -O girassol é uma oleaginosa de grande importância agroenergética e o nitrogênio é considerado um dos fatores limitantes para seu crescimento e produção. O objetivo deste trabalho foi avaliar a absorção de nitrogênio (alto e baixo suprimento de nitrato e amônio) e determinar os parâmetros cinéticos (K m e V max ) de absorção desses íons em plantas de girassol (híbrido Neon). O experimento foi conduzido em câmara de crescimento utilizando-se sistema hidropônico. Foram aplicados os seguintes tratamentos: 0,2 e 2,0 mmol L -1 de N-NO 3 -e N-NH 4 + . Foram determinados os parâmetros cinéticos (K m e V max ) da absorção de nitrato e amônio, bem como as frações solúveis -. N-NH 4 + , N-amino e açúcares) e N-total em diferentes tecidos das plantas de girassol. As plantas cultivadas com amônio exibiram maior V max quando comparadas com as cultivadas com nitrato. Altas doses de amônio provocaram redução no volume radicular e as plantas supridas com 2,0 mmol L -1 de N-NO 3 -produziram maior biomassa de raízes e parte aérea. Os maiores teores de N-NO 3 -foram encontrados nos pecíolos. Analisados em conjunto, os dados sugerem maior potencial de utilização de N nítrico como fonte de nitrogênio para a adubação nitrogenada no cultivo de girassol. Palavras-chave:Helianthus annuus L.. Oleaginosa. N-total. Nitrogênio.

δ15N values in plants are determined by both nitrate assimilation and circulation

“…In fact, roots were a site of nitrate accumulation, with very high nitrate content up to 80 µmol g −1 DW in sunflower (Fig. 3), as observed previously (Alves et al , 2016). The presence of two nitrate pools in roots has been demonstrated – although the biochemical nature of these two pools (cytosolic vs. vacuolar, apoplastic vs. symplastic, and so on) remains uncertain (Ferrari et al , 1973; MacKown et al , 1983; Siddiq et al , 1991; Devienne et al , 1994; Miller & Smith, 1996).…”

Contribution of dark septate fungi to the nutrient uptake and growth of rice plants

“…During 11 h, samples of the solution were then collected every 30 min by removing 0.5 mL aliquots from each pot to plot the depletion curves and determine the kinetic parameters V max and K m . 48 , 49 The samples were placed in microtubes and the NO 3 − concentration was measured according to 50 as adjusted following Alves et al 51 The V max and K m values were determined by using the mathematical graphing method proposed by Cometti et al 52 with the Cineticawin 1.0 program (Universidade Federal de Viçosa, Minas Gerais, Brazil).…”

Ammonium Nitrogen Tolerant Chlorella Strain Screening and Its Damaging Effects on Photosynthesis

“…Free nitrogen molecules in the atmosphere can be converted into combined nitrogen via atmospheric, industrial, and biological nitrogen fixation (Lanyon, 1995; Nishibayashi et al, 2004; Olivares et al, 2013). Combined nitrogen, primarily ammonium nitrogen and nitrate nitrogen, subsequently become the objects of intense competition among plants and microorganisms (Costa et al, 2001; Alves et al, 2016). Ammonium nitrogen can be directly assimilated into amino acids via the enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT) (Wu et al, 2016), whereas nitrate nitrogen must first be reduced to nitrite nitrogen in the cytosol, after which it is immediately reduced to ammonium nitrogen in chloroplasts or plastids (Monier et al, 2015).…”