1. Plant Nitrogen Assimilation and Use Efficiency
03/21/2012

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)

12. outline GENETICALLY CONTROLLED DIFFERENCES IN NITROGEN USE EFFICIENCY
AGRONOMY EFFICIENCY OF SOIL NITROGEN AND FERTILIZER NITROGEN

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

18. AGRONOMY EFFICIENCY OF SOIL NITROGEN AND FERTILIZER NITROGEN
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)