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Plant Nitrogen Assimilation and Use Efficiency

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Presentation on theme: "Plant Nitrogen Assimilation and Use Efficiency"— Presentation transcript:

1 Plant Nitrogen Assimilation and Use Efficiency

2 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)

3 Pathway of nitrogen from rhizosphere to seeds
N efflux and N transportation and remobilization N assimilation N acquisition Rhizosphere

4 N forms and concentration changes in Rhizosphere
aerobic soils nitrate flooded/acidic soils ammonium (Kirk GJD, Kronzucker HJ. 2005)

5 low external concentrations (1 μM to 1 mM)
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) CHATS available even when plants have not been previously supplied with NO3−

6 Nitrogen assimilation
(Masclaux-Daubresse C, et al., 2010)

7 Nitrogen remobilization
95% of seed protein is derived from amino acids

8 Nitrogen transportation
NTR1s: nitrate transporter (Kirk GJD, Kronzucker HJ. 2005)

9 Nitrogen efflux ATP-dependant H+-pumping activity low-affinity
(Kirk GJD, Kronzucker HJ. 2005) nitrate efflux transport activity (Km = 5 mM).

10 Volatile nitrogen losses
imbalance between N accumulation and N assimilation gaseous N losses: 40 kg of N/ha (soybean and maize)

11 Young leaves senescing leaves (Masclaux-Daubresse C, et al., 2010)


13 Natural Variation in Different Genotypes of the Same Plant Species
Genetic variation total N uptake postanthesis N uptake N translocation N assimilation Accurate fertilizer N for different cultivars developmental stages harvest stage Ex: tillers, HI↑ NpUE↑

14 Favorable alleles for breeding
N uptake & remobilization genes are independently inherited traits Modulating the activities of enzymes which related to high NUE Ex:GS1 & GS2 in wheat

15 genotype & genotype × N fertilization level
Variation of Nitrogen Use Efficiency at Limited and Sufficient Nitrogen Conditions genotype & genotype × N fertilization level Low N supplies High N inputs Major changes of NUE N remobilization NUtE (maize and arabidopsis) NUpE (wheat) N uptake (postanthesis N uptake) Result in NUE and NRE ↑ NUE and NRE ↓

16 Nitrogen use efficiency (NUE)
Biomass or Yield(N)-Biomass or Yield(C)/ fertilizer N Nitrogen uptake efficiency (NUpE) Root acquire(N) - root acquire/fertilizer N Nitrogen utilization (assimilation) efficiency (NUtE) the capacity of plant roots to acquire N from the soil (commonly referred to as the percentage of fertilizer N acquired by plant) Nitrogen Remobilization efficiency (NRE) the ratio of N remobilization from source or senescent leaves to that of sink leaves or developing grains (seeds)

17 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

Soil and Fertilizer Nitrogen Use Efficiency Integrated Nutrient Management in Intensive Agriculture

19 Soil and Fertilizer Nitrogen Use Efficiency
Soil surface Leaching Ground water Denitrification to N2 Soil erosion Fluxes to atomosphere Volatilization Mismatching of N availability with crop needs is probably the single greatest contributor to excess N losses

20 fertilizer application
Base on leaf chlorophyll level & N concentration deep placement, controlled release materials multiple-split applications biological sources of supplement fertilizer N Azolla and legumes

21 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

22 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)

23 Cytosolic pH Balance Rice prefer ammonium than nitrate
alkalinization in the cytoplasm influences pH homeostasis ammonium and nitrate uptake


25 pH balance, N & organic acid metabolism
A tonoplast dicarboxylate (malate and fumarate) transporter (AttDT) C-N metabolism pH balance, N & organic acid metabolism

26 Increasing Yield and Nitrogen Harvest Index
NUpE N losses from soil NUtE and NpUE N concentration Target : improve the grain yield per unit of N application A low seed N concentration HI and NHI are highly correlated

27 Gln1-3 : specific to grain production (Martin, 2006)
Gpc-B1 :enhancing N remobilization from source leaves to the seeds (Uauy, 2006) Asn synthetase 1 : enhancing HI and N remobilization from vegetative tissues to the seeds (Masclaux-Daubresse, 2010)


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