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Plant Nitrogen Assimilation and Use Efficiency. 03/21/2012. relative amount of nitrate. Nonlegume plants: 20–50 g of N 1 kg of dry biomass 44 million tons for 9 billion people by 2050. ( Dechorgnat J, et al., 2011) . Pathway of nitrogen from rhizosphere to seeds. N efflux and

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relative amount of nitrate
relative amount of nitrate
  • Nonlegume plants: 20–50 g of N 1 kg of dry biomass
  • 44 million tons for 9 billion people by 2050

(Dechorgnat J, et al., 2011)

pathway of nitrogen from rhizosphere to seeds
Pathway of nitrogen fromrhizosphere to seeds
  • N efflux and
  • N transportation and remobilization
  • N assimilation
  • N acquisition
  • Rhizosphere
n forms and concentration changes in rhizosphere
N forms and concentration changes in Rhizosphere
  • aerobic soils nitrate
  • flooded/acidic soils ammonium

(Kirk GJD, Kronzucker HJ. 2005)

nitrogen acquisition
Nitrogen acquisition

low external concentrations (1 μM to 1 mM)

  • transport system :
      • high affinity transport system (HATS)
        • constitutive system (cHATS)
        • inducible system (iHATS)
      • low affinity transport system (LATS)
nitrogen assimilation
Nitrogen assimilation

(Masclaux-Daubresse C, et al., 2010)

nitrogen remobilization
Nitrogen remobilization
  • 95% of seed protein is derived from amino acids
nitrogen transportation
Nitrogen transportation
  • NTR1s: nitrate transporter

(Kirk GJD, Kronzucker HJ. 2005)

nitrogen efflux
Nitrogen efflux
  • ATP-dependant H+-pumping activity
  • low-affinity

(Kirk GJD, Kronzucker HJ. 2005)

volatile nitrogen losses
Volatile nitrogen losses
  • imbalance between N accumulation and N assimilation
  • gaseous N losses: 40 kg of N/ha (soybean and maize)
outline
outline
  • GENETICALLY CONTROLLED DIFFERENCES IN NITROGEN USE EFFICIENCY
  • AGRONOMY EFFICIENCY OF SOIL NITROGEN AND FERTILIZER NITROGEN
natural variation in different genotypes of the same plant species
Natural Variation in DifferentGenotypes of the Same Plant Species
  • Genetic variation
  • total N uptake
  • postanthesisN uptake
  • N translocation
  • N assimilation
  • Accurate fertilizer Nfor different cultivars
  • developmental stages
  • harveststage

Ex: tillers, HI↑

NpUE↑

favorable alleles for breeding
Favorable alleles for breeding
  • N uptake & remobilization genes are independently inherited traits
  • Modulating the activities of enzymes which related to high NUE
  • Ex:GS1&GS2in wheat
variation of nitrogen use efficiency at limited and sufficient nitrogen conditions
Variation of Nitrogen Use Efficiency at Limited and Sufficient Nitrogen Conditions
  • genotype & genotype N fertilization level
strategy of breeding high nue cultivars
Strategy of breeding high-NUE cultivars
  • high-yield breeding in Chinese maize

Root growth was improved only under N-sufficient conditions

  • root growth traits have been inadvertently selected to adapt to the increasing N supply in the environment
  • Genetical materials of Arabidopsis was unaffected by N supply levels at the vegetative stage
  • breeding high-NUE cultivars should occur under conditions of moderate N supply
agronomy efficiency of soil nitrogen and fertilizer nitrogen
AGRONOMY EFFICIENCY OF SOIL NITROGEN AND FERTILIZER NITROGEN
  • Soil and Fertilizer Nitrogen Use Efficiency
  • Integrated Nutrient Management in Intensive Agriculture
soil and fertilizer nitrogen use efficiency
Soil and Fertilizer Nitrogen Use Efficiency
  • Mismatching of N availability with crop needs is probably the single greatest contributor to excess N losses

Soil surface

  • Leaching
  • Ground water
  • Denitrification to N2
  • Soil erosion

Fluxes to atomosphere

Volatilization

fertilizer application
fertilizer application
  • Base on leaf chlorophyll level & N concentration

deep placement,

controlled release materials

multiple-split applications

  • biological sources of supplement fertilizer N

Azollaand legumes

integrated nutrient management in intensive agriculture
Integrated Nutrient Management in Intensive Agriculture
  • management tools

Rotations

Intercropping

perennial crops

  • site-specific conditions to decrease N losses and optimize crop performance
  • remote sensing of the visible light reflected
root nue
Root & NUE

In previous review

  • a root system that is more efficient at taking up N
  • maintaining root activity enhance NUpE

Nitrate and ammonium transporter (NRT, AMT)

(Werner, 2010)

cytosolic ph balance
Cytosolic pH Balance

Rice prefer ammonium than nitrate

  • alkalinization in the cytoplasm
  • influences pH homeostasis
  • ammonium and nitrate uptake
slide23

A tonoplastdicarboxylate

(malate and fumarate) transporter (AttDT)

  • C-N metabolism
  • pH balance, N & organic acid metabolism
increasing yield and nitrogen harvest index
Increasing Yield and Nitrogen Harvest Index
  • NUpEN losses from soil
  • NUtEand NpUEN concentration
  • Target : improve the grain yield per unit of N application
    • A low seed N concentration
  • HI and NHI are highly correlated
slide25

Gln1-3 : specific to grain production (Martin, 2006)

  • Gpc-B1 :enhancing N remobilization from source leaves to the seeds (Uauy, 2006)
  • Asnsynthetase 1 : enhancing HI and N remobilization from vegetative tissues to the seeds (Masclaux-Daubresse, 2010)