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Grantee Research Project Results

NCER Grantee Research Project Results

Differences in Nitrogen Uptake Between Mycorrhizal Bromus Madritensis and Artemisia Californica

EPA Grant Number: U914994
Title: Differences in Nitrogen Uptake Between Mycorrhizal Bromus Madritensis and Artemisia Californica
Investigators: Yoshida, Lidia C.
Institution: University of California - Riverside
EPA Project Officer: Edwards, Jason
Project Period: January 1, 1996 through January 1, 1999
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996)
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems

Description:

Objective:

The objectives of this research project were to: (1) to determine the effect of two forms of nitrogen (N), ammonium (NH4+), and nitrate (NO3-), on the growth and mycorrhizal infection of Artemisia californica Less. (California sagebrush) and Bromus madritensis ssp. rubens L. Husnot (foxtail chess),; (2) to examine the short -term fate of N supplied as 15N-NH4 and 15N-NO3 to Bromus and Artemisia, and to discern whether there are any differences in the form of N taken up by the plants due to the presence of its mycorrhizal fungi; and (3) to determine whether there is any competition between Artemisia and Bromus for either form of N when mycorrhizal plants are grown together in the field.

Approach:

Seeds of Artemisia and Bromus were sown in pots, and given the following treatments in a factorial plant growth experiment: (1) inoculation with mycorrhizal spore inoculum; and (2) 50 ppm of NH4+ or NO3-, using NH4Cl or Ca(NO3)2, simulating high N deposition conditions. After 8 weeks, the plants were harvested, and the roots and shoots were dried and weighed for biomass determination. Shoots were ground and analyzed for C and N with a Carlo Erba CNS analyzer, and roots were examined for mycorrhizal colonization. To study the nature of NO3- and NH4+ uptake by Artemisia and Bromus separately, mycorrhizal plants were grown in another set of greenhouse experiments. Mycorrhizal plants were grown for 7 weeks, supplied with 4.3 mM K15NO3 or (15NH4)2SO4, then harvested after 24 hours. Roots were assessed for mycorrhizal colonization. Leaf and root tissue were ground and analyzed by isotope ratio mass spectrometry to assess N and 15N concentrations. To understand how N deposition might affect competition between Artemisia and Bromus, field plots were prepared with mycorrhizal inoculum. Artemisia and Bromus seedlings were planted in monoculture or were (b) mixed. Plant pairs were supplied with 15N, harvested after 24 and 72 hours, and for N and 15N concentration and mycorrhizal colonization.

Supplemental Keywords:

fellowship, nitrogen uptake, Bromus madritensis, Artemisia California, micorrhizal infection, colonization, isotope ratio mass spectrometry, nitrogen deposition, nitrogen concentration.

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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