Contribution of the Root System to Nitrate Assimilation in Whole Cotton Plants.

Radin, JW

doi:10.1071/pp9770811

Cited by 32 publications

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“…The variation in these percetitages reflects the (so far tmknown) presence or absence, respectively, of shoot NR activity in situ in the dark (cf. Abrol et al, 1983, Radin 1977, Reed et al, 1983, Secondly, the RQ found for roots utilizing nitrate was 0.9 to 1,0 (Tab, 2), These values indicate a low NR activity in the roots, since high rates of nitrate reduction lead to a high RQ, as fotind ie roots of white lupin (Lambers et al 1980) atid in excised roots of barley (Willis and Yemm 1955),…”

Section: Carbon Dioxide Measurementsmentioning

confidence: 99%

Efficiency of respiration and energy requirements of N assimilation in roots of Pisum sativum

Devisser

1985

Physiologia Plantarum

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Ries de Visserde Visser, R, 1985, Efficiency of respiration and energy requiretnents of N assimilation in roots of Pisiun sativum. Plant, The function of alternative path respiration in roots was investigated in pea plants (Pisum sativum L, cv. Rondo), Plants were grown in symbiosis with Rhizobium leguminosarum (strain PF2), cotnpletely dependent on N^ fijtation, or non-nodulated, receiving nitrate or ammonium at the same rate as Nj was fixed in symbiosis. Under these conditions, relative growth rates of plants grown with N,, NOj or NHJ were the same. This facilitated interpretation of the effect of the N source on the efficiency of root respiration, as determined by the relative activity of the non-phosphorylating alternative path. The 'wasteful' oxidation of carbohydrate via this pathway was defined as the glucose equivalent of the difference between the amounts of ATP (mol O;)"' produced in cytochrome and alternative path respiration, 'Wasteful' carbohydrate oxidation maximally amounted to 4% (NJ, 15% (NOj") and 25% (NH^) of the daily carbohydrate oxidation in the roots. It is concluded that the 'wasteful' oxidation of carbohydrate via the alternative path is of minor importance for the adaptation of root respiratory metabolism to different energy requirements of N assimilation. The total carbohydrate import by roots fixing N, was ca 60 and 30% higher than the import by roots assimilating NO,^ or NHj", respectively. Two factors are shown to account for these differences: the high carbohydrate cost of N, fixation, and the small contribution (30%) of the roots to NO3" reduction by the plant. The high carbohydrate requirements of roots fixing N2 were met by higher rates of photosynthesis as compared with piants utilizing NO3" or NH,,

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Section: Carbon Dioxide Measurementsmentioning

confidence: 99%

Efficiency of respiration and energy requirements of N assimilation in roots of Pisum sativum

Devisser

1985

Physiologia Plantarum

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“…NRA assayed in vivo without additional NO − 3 best approximated NO − 3 assimilation rates in situ in cotton ( G. hirsutum ) (Radin et al, 1975). Consequently, this assay was used to study regulation of NO − 3 assimilation in cotton (Radin et al, 1975; Radin, 1977) and to determine the partitioning of NO − 3 between shoots and roots in most legume (Andrews et al, 1984) and grass (Andrews et al, 1992; Jiang and Hull, 1999) species. Further, the NRA assay in vivo has been suggested for use as a tool in monitoring systems that determine the changes of N concentration in cotton leaves (Chu et al, 1989).…”

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Diurnal Fluctuations of Nitrate Uptake and In Vivo Nitrate Reductase Activity in Pima and Acala Cotton

2001

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This study was conducted to determine whether diurnal fluctuations of nitrate reductase activity in two cotton species, Pima (Gossypium barbadense L.) and Acala (Gossypium hirsutum L.), are regulated by NO−3 uptake or leaf NO−3 concentration. The two species differ greatly in their N use efficiency. The seedlings were grown for 25 d in nutrient solutions containing 0.05, 0.10 or 1.0 mM NO−3 under a 14‐h light/10‐h dark cycle at 30°C/20°C. Uptake rates were measured by following NO−3 depletion from the uptake solutions at 20°C or 30°C. Nitrate reductase activity (NRA) in fully expanded first true leaves was determined by an anaerobic method in vivo. Upon illumination uptake rates for both species, measured at 30°C, increased until they plateaued in about 5 h and were maintained at that level for the remainder of the light period and the following dark cycle. When measured at 20°C in the dark, however, the uptake rates decreased 25 to 30% for the first 3 h and then remained constant. Leaf NRA increased rapidly during the first hour of illumination, reached a plateau and then decreased after 4 to 6 h of illumination. The decline was more rapid when NRA was assayed in the absence of NO−3 In darkness, NRA levels were low and did not fluctuate. Upon illumination, leaf NO−3 concentration also increased for about 7 h and then decreased gradually. The results indicate that (i) the diurnal rhythm of NO−3 uptake is modulated by temperature rather than by light/dark transitions, and (ii) while the increase in NRA upon illumination may be regulated by NO−3 flux from roots to shoots, the decrease in NRA under prolonged illumination is independent of that flux.

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“…A maioria das espécies herbáceas, incluindo importantes culturas econômicas, reduzem nitrato tanto nas raízes como nas folhas. Em culturas como o algodão (RADIN, 1977), cevada (CHANTAROTWONG et ai., 1976;ASLAM & HUFFAKER, 1982;LEWIS et ai., 1982), soja (CRAFTS-BRANDNER & HARPER, 1982) e milho (HAGEMAN & FLESHER, 1960;WALLACE, 1973), os níveis de redutase de nitrato são mais altos na parte aérea do que nas raízes. Em outras espécies, como girassol (WEISSMAN, 1972), tremoço e rabanete (PATE, 1980), as raízes apresentam atividade bem maior do que a das folhas.…”

Section: Introductionunclassified

Distribuição da assimilação de nitrato e de matéria seca em plantas jovens de café cultivadas em diferentes níveis de nitrogênio

Carelli

Fahl

1991

Bragantia

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Foi estudado o efeito de níveis de nitrogênio na distribuição do processo de redução de nitrato e de matéria seca entre as raízes e a parte aérea, em plantas de café de nove meses de idade, cultivadas em areia em casa de vegetação e irrigadas com soluções nutritivas contendo 3,75, 7,5 e 15mM de nitrato. A área foliar e a matéria seca das folhas aumentaram com o nível de nitrato das soluções, enquanto a matéria seca das raízes e o número de pares de folhas no ramo ortotrópico não foram alterados. A atividade in vivo da redutase de nitrato nas raízes mais jovens foi bem maior do que a das folhas recém-expandidas e aumentou com a concentração de nitrato no meio de crescimento. Os valores da atividade enzimática, quando determinada com a adição de nitrato no meio de reação, foram superiores às análises sem nitrato, sugerindo que a atividade da redutase de nitrato nas raízes e, principalmente, nas folhas, foi limitada pela quantidade de substrato. O aumento na disponibilidade de nitrogênio para as plantas proporcionou maior crescimento da parte aérea, em relação às raízes.

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Contribution of the Root System to Nitrate Assimilation in Whole Cotton Plants.

Cited by 32 publications

References 0 publications

Efficiency of respiration and energy requirements of N assimilation in roots of Pisum sativum

Efficiency of respiration and energy requirements of N assimilation in roots of Pisum sativum

Diurnal Fluctuations of Nitrate Uptake and In Vivo Nitrate Reductase Activity in Pima and Acala Cotton

Distribuição da assimilação de nitrato e de matéria seca em plantas jovens de café cultivadas em diferentes níveis de nitrogênio

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