Pea Pisum sativum cv' Oregon Sugar Responses to Fertilizer Nitrate Supply

1
Pea (Pisum sativum cv. Oregon Sugar) Responses to
Fertilizer Nitrate Supply

• JulieAnn Rader 2007

2
(No Transcript)
3
Nitrogen Sources

• Seed nitrogen

4
Nitrogen Sources

• Seed nitrogen
• Nitrate-N or ammonium-N assimilation from soil or
  fertilizer

5
Nitrogen Sources

• Seed nitrogen
• Nitrate-N or ammonium-N assimilation from soil or
  fertilizer
• Biological nitrogen fixation

6
Nitrogen Fixation

• Atmospheric nitrogen is fixed to ammonia by
  nitrogenase enzymes
• N2 8 H 8 e- 2 NH3 H2

nitrogenase
7
Nitrogen Fixation

• Atmospheric nitrogen is fixed to ammonia by
  nitrogenase enzymes
• N2 8 H 8 e- 2 NH3 H2

nitrogenase
8
Nodulated roots of a pea legume
9
Fixation Process
10
Fixation Process
11
Fixation Process
12
Photosynthetic Carbon Cost

• Carbon energy required to obtain nitrogen from
  any external nitrogen source

13
Previous Studies

• Pate (1971) Nitrogen fixation decreases when
  increased nitrate is available
• Viosin et al. (2003) More photosynthetic carbon
  was allocated to nodules of nitrogen fixing
  plants as opposed to roots of plants assimilating
  nitrate-N
• Mahon (2001) Plant photosynthesis rates were
  higher in plants fixing nitrogen than
  assimilating nitrate-N

14
Goals

• To determine the effects of fertilizer nitrate-N
  concentration on nitrogen fixation by pea plants
  (Pisum sativum cv. Oregon Sugar)
• To determine if the carbon energy requirement for
  nitrogen fixation is different from fertilizer
  nitrate-N assimilation

15
Shaded and non-shaded pea plants
16
Hypotheses

• Based on Pate Nitrogen fixation would decrease
  as fertilizer nitrate-N concentrations increased
• 2. Based on Voisin et al. and Mahon Plants
  fixing nitrogen would have a greater carbon
  energy requirement than plants assimilating
  nitrate-N from fertilizer

17
Methods Nitrate Fertilizers

• Five fertilizers with the following nitrate-N
  concentrations
• 0 (control) µg/mL
• 10 µg/mL
• 30 µg/mL
• 100 µg/mL
• 500 µg/mL

18
Methods Isotope Labeling

• Fertilizer nitrate-N was labeled with 15N
• Assimilated nitrogen quantified by mass
  spectroscopy

19
Methods Mass Spectroscopy
ionization
20
Methods Mass Spectroscopy
ionization
magnetic field
acceleration
21
Methods Mass Spectroscopy
ionization
magnetic field
acceleration
14N
15N
22
Methods Mass Spectroscopy
ionization
magnetic field
acceleration
14N
15N
detection
23
Methods Photosynthesis Chamber
24
Methods Net Photosynthesis
25
Methods Net Photosynthesis
26
Methods Net Photosynthesis
LI-COR CO2 analyzer
27
LI-COR CO2 analyzer
28
Results
(µg/mL)
29
Results
(µg/mL)
30
Results
(µg/mL)
31
Results
(µg/mL)
32
Results
(µg/mL)
33
Results
(µg/mL)
34
Results
(µg/mL)
µ
35
Results
(µg/mL)
36
Conclusions

• Hypothesis supported nitrogen fixation decreased
  as fertilizer nitrate-N concentrations increased

37
Conclusions

• Hypothesis supported nitrogen fixation decreased
  as fertilizer nitrate-N concentrations increased
• Nitrogen fixation began to decline only after
  concentrations exceeded 30 µg/mL nitrate-N

38
Conclusions

• Hypothesis supported nitrogen fixation decreased
  as fertilizer nitrate-N concentrations increased
• Nitrogen fixation began to decline only after
  concentrations exceeded 30 µg/mL nitrate-N
• Nitrogen fixed by shaded plants was lower than
  plants grown in light

39
Conclusions

• Hypothesis supported nitrogen fixation decreased
  as fertilizer nitrate-N concentrations increased
• Nitrogen fixation began to decline only after
  concentrations exceeded 30 µg/mL nitrate-N
• Nitrogen fixed by shaded plants was lower than
  plants grown in light
• Nitrogen fixation increased from five to seven
  weeks in all plants

40
Limitations

• No relationship between net photosynthesis and
  nitrate-N concentration was found

41
Limitations

• No relationship between net photosynthesis and
  nitrate-N concentration was found
• No success in determining carbon energy
  requirements for nitrogen fixation vs. fertilizer
  nitrate-N assimilation

42
Future Work

• Pinpoint where nitrogen fixation begins to
  decline by applying fertilizer nitrate-N
  concentrations between 30 and 100 µg/mL to pea
  plants
• Measure net photosynthesis rates and repeat study

43
Acknowledgements

• Dr. Michael Russelle
• United States Department of Agriculture
• University of Minnesota
• Ms. Fruen
• Team Research

44
Pea (Pisum sativum cv. Oregon Sugar) Responses to
Fertilizer Nitrate Supply

• JulieAnn Rader 2007