Root growth as a function of ammonium and nitrate in the root zone

Bloom, Arnold J.; Jackson, Louise E.; Smart, David R.

doi:10.1111/j.1365-3040.1993.tb00861.x

Cited by 80 publications

(43 citation statements)

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“…Roots growing in the presence of low levels of nutrients displayed higher nitrogen uptake capacities on a root weight basis, in agreement with the majority of studies (Bloom et al 1993;Crawford 1995). This is due to an increase in the number of transporters per unit root area in the presence of low concentrations of nutrients (Bloom et al 1993;George et al 1995). The higher nitrate uptake rates observed for the elongation and younger zone (yellow parts of the root) of the mycorrhizal plants grown with low levels of nutrients may be due to the presence of the fungi, since these areas have the highest rates of AM colonisation.…”

Section: Discussionsupporting

confidence: 91%

“…This gradient was still visible when assessed on the basis of root pigmentation, with higher uptake rates through the white and yellow parts of the root. Roots growing in the presence of low levels of nutrients displayed higher nitrogen uptake capacities on a root weight basis, in agreement with the majority of studies (Bloom et al 1993;Crawford 1995). This is due to an increase in the number of transporters per unit root area in the presence of low concentrations of nutrients (Bloom et al 1993;George et al 1995).…”

Section: Discussionsupporting

confidence: 86%

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Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity

Cruz

Green²,

Watson³

et al. 2003

Mycorrhiza

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The aim of this research was to investigate the effect of arbuscular mycorrhizal (AM) colonisation on root morphology and nitrogen uptake capacity of carob (Ceratonia siliqua L.) under high and low nutrient conditions. The experimental design was a factorial arrangement of presence/absence of mycorrhizal fungus inoculation (Glomus intraradices) and high/low nutrient status. Percent AM colonisation, nitrate and ammonium uptake capacity, and nitrogen and phosphorus contents were determined in 3-month-old seedlings. Grayscale and colour images were used to study root morphology and topology, and to assess the relation between root pigmentation and physiological activities. AM colonisation lead to a higher allocation of biomass to white and yellow parts of the root. Inorganic nitrogen uptake capacity per unit root length and nitrogen content were greatest in AM colonised plants grown under low nutrient conditions. A better match was found between plant nitrogen content and biomass accumulation, than between plant phosphorus content and biomass accumulation. It is suggested that the increase in nutrient uptake capacity of AM colonised roots is dependent both on changes in root morphology and physiological uptake potential. This study contributes to an understanding of the role of AM fungi and root morphology in plant nutrient uptake and shows that AM colonisation improves the nitrogen nutrition of plants, mainly when growing at low levels of nutrients.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 86%

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity

Cruz

Green²,

Watson³

et al. 2003

Mycorrhiza

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“…Positive effects of ammonium on plant Van Dijk & Roelofs, 1988;Schulze, Oren & Lange, growth have been observed at low ammonium 1989). Ammonium toxicity may have several causes, concentrations (Bloom, Jackson & Smart, 1993). At which are not easily distinguished.…”

Section: Introduction |J^g ^J^j Nitrification Is Slowed Down In Acidimentioning

confidence: 99%

Solute content and energy status of roots of barley plants cultivated at different pH on nitrate‐ or ammonium‐nitrogen

Lang¹,

Kaiser²

1994

New Phytologist

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SUMMARYBarley seedlings (Hordeum vulgare cv. 'Gaulois') were precultured hydroponically for 4 d on nutrient solutions with nitrate (3 mM) as N-source at pH 4-7, and were then transferred to solutions with ammonium or nitrate as N-source (3 mM), buffered and adjusted to different pH (4-0, 5-5, 6-8). Variations in shoot and root growth and solute contents were examined and grouped into pH-effects, ammonium effects and interactions.Shoot biomass was not affected under all conditions. Root fresh weight was insensitive to the external pH when nitrate was the N-source, but was drastically affected by a combination of ammonium and low pH. In contrast, root length was negatively affected by low pH per sc.In nitrate-grown plants, ammonium levels in roots and shoots were low (0-5 to 1 mM). After transfer of plants to ammonium solution, roots accumulated ammonium within 24 h about sixfold (18 mM) above the external concentration. At pH 5-5 or 6-8, but not at pH 4, root ammonium contents decreased afterwards to a lower steady state value (10 mM). Leaves also accumulated ammonium, especially at the most acidic pH.Concentrations of major inorganic cations in roots were markedly but differentially affected by acidic pH and ammonium. The magnesium content of roots was drastically decreased (from 18 to 2 mM) by ammonium nutrition, and this was independent of the external pH. In contrast, calcium levels in roots were decreased by low external pH, independent of the N-source. Potassium levels in roots were rather insensitive to both low pH and ammonium.The pH of crude root homogenates was measured in order to obtain at least crude information about trends in possible cellular pH changes. At an external pH of 4-0 and 5-5, the pH of the homogenates was 5-8, and it increased to 6-3 when the external pH was 6-8. The pH of the homogenates was not affected by the N-source.In spite of the drastic effects of the N-source on the concentration of ammonium and magnesium in root tissues, ATP/ADP-ratios were not affected. Also, sugar levels were unchanged or even increased. Thus, growth impairment could not be traced back to impaired carbohydrate or ATP-supply, which might occur as a consequence of ammonium accumulation or Mg''^-deficiency.

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“…Most likely, AMT1;1 assembles as a trimer and the phosphorylation signal transinhibits the two neighboring subunits, representing an example of cooperative transporter regulation . The tightly controlled transport of ammonium is not only essential for maintaining the cation-anion balance and plant growth (Bloom et al, 1993;Marschner, 1995) but also for adjusting levels of phytohormones regulating leaf development (Walch-Liu et al, 2000;Rahayu et al, 2005) and for preventing overaccumulation of ammonium that may otherwise cause membrane depolarization and cellular damage (Britto and Kronzucker, 2002).…”

Section: Introductionmentioning

confidence: 99%

The Organization of High-Affinity Ammonium Uptake in Arabidopsis Roots Depends on the Spatial Arrangement and Biochemical Properties of AMT1-Type Transporters

et al. 2007

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The AMMONIUM TRANSPORTER (AMT) family comprises six isoforms in Arabidopsis thaliana. Here, we describe the complete functional organization of root-expressed AMTs for high-affinity ammonium uptake. High-affinity influx of 15 N-labeled ammonium in two transposon-tagged amt1;2 lines was reduced by 18 to 26% compared with wild-type plants. Enrichment of the AMT1;2 protein in the plasma membrane and localization of AMT1;2 promoter activity in the endodermis and root cortex indicated that AMT1;2 mediates the uptake of ammonium entering the root via the apoplasmic transport route. An amt1;1 amt1;2 amt1;3 amt2;1 quadruple mutant (qko) showed severe growth depression under ammonium supply and maintained only 5 to 10% of wild-type high-affinity ammonium uptake capacity. Transcriptional upregulation of AMT1;5 in nitrogen-deficient rhizodermal and root hair cells and the ability of AMT1;5 to transport ammonium in yeast suggested that AMT1;5 accounts for the remaining uptake capacity in qko. Triple and quadruple amt insertion lines revealed in vivo ammonium substrate affinities of 50, 234, 61, and 4.5 mM for AMT1;1, AMT1;2, AMT1;3, and AMT1;5, respectively, but no ammonium influx activity for AMT2;1. These data suggest that two principle means of achieving effective ammonium uptake in Arabidopsis roots are the spatial arrangement of AMT1-type ammonium transporters and the distribution of their transport capacities at different substrate affinities.

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Root growth as a function of ammonium and nitrate in the root zone

Cited by 80 publications

References 50 publications

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity

Solute content and energy status of roots of barley plants cultivated at different pH on nitrate‐ or ammonium‐nitrogen

The Organization of High-Affinity Ammonium Uptake in Arabidopsis Roots Depends on the Spatial Arrangement and Biochemical Properties of AMT1-Type Transporters

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