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

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Presentation on theme: "Plant Nitrogen Assimilation and Use Efficiency 03/21/2012."— Presentation transcript:

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

2 Nonlegume plants: 20–50 g of N 1 kg of dry biomass 44 million tons for 9 billion people by 2050 relative amount of nitrate (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 aerobic soils nitrate flooded/acidic soils ammonium (Kirk GJD, Kronzucker HJ. 2005) N forms and concentration changes in Rhizosphere

5 transport system : high affinity transport system (HATS) – constitutive system (cHATS) – inducible system (iHATS) low affinity transport system (LATS) low external concentrations (1 μM to 1 mM) Nitrogen acquisition

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

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

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

9 ATP-dependant H + - pumping activity low-affinity (Kirk GJD, Kronzucker HJ. 2005) Nitrogen efflux

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

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

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 Variation of Nitrogen Use Efficiency at Limited and Sufficient Nitrogen Conditions Low N suppliesHigh N inputs Major changes of NUEN remobilization NUtE (maize and arabidopsis) NUpE (wheat) N uptake (postanthesis N uptake) Result inNUE 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 Mismatching of N availability with crop needs is probably the single greatest contributor to excess N losses Leaching Ground water Denitrification to N 2 Soil erosion Volatilization Fluxes to atomosphere Soil surface

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 (Werner, 2010) Nitrate and ammonium transporter (NRT, AMT)

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

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

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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