Grantee Research Project Results
Physiological Controls of NO2 Uptake by Corn (Zea Mays)EPA Grant Number: U915141
Title: Physiological Controls of NO2 Uptake by Corn (Zea Mays)
Investigators: Hereid, Daniel P.
Institution: University of Colorado at Boulder
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1997 through January 1, 1999
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1997)
Research Category: Academic Fellowships , Air Quality and Air Toxics , Fellowship - Atmospheric Sciences
The objective of this research project is to investigate the processes that control the atmospheric uptake of nitrogen dioxide (NO2) by corn plants. Variables analyzed include NO2 concentration, light intensity, seasonal variation, leaf canopy location, and leaf nitrogen status.Approach:
The experimental system I use involves enclosing part of a leaf in the leaf cuvette of a portable photosynthesis system, which measures photosynthetic rate, transpiration, stomatal conductance, and several related parameters. This system also has the ability to tightly control conditions within the cuvette, such as temperature, light, and CO2 concentration. Several known NO2 concentrations are delivered to the cuvette by introducing NO2 from a compressed gas cylinder into the incoming air stream. The concentration of NO2 exposed to the leaf is varied from 0.5 to 30 ppb. NO2 concentrations are measured in the sample air with a chemiluminescent NO2 detector. NO2 is initially passed through the system with an empty cuvette until the background level of NO2 equilibrates. A leaf then is enclosed in the cuvette, and the difference between the NO2 concentration of the empty cuvette and the leaf-filled cuvette is attributed to the assimilation or emission of NO2 by the leaf. Variables that have been investigated in field-grown corn include ambient NO2 concentration, light intensity, leaf age, and leaf location in the canopy. The field measurements were conducted by the National Oceanic and Atmospheric Administration (NOAA) as part of a large field campaign. This campaign also addressed the question of the role of biogenic uptake of NO2 in atmospheric chemistry. NOAA's work included tower flux and aircraft measurements, and there are future plans to compare our measurements to address the question of scale. I also am taking measurements on greenhouse grown plants. Corn plants have been grown with different levels of nitrogen fertilization to determine if the uptake rate of NO2 is related to leaf-level nitrogen status. Additionally, greenhouse plants are being used to investigate the importance of stomatal control and leaf age on NO2 uptake.Supplemental Keywords:
fellowship, atmospheric uptake, nitrogen dioxide, corn plants, nitrogen dioxide concentration, photosynthesis, photosynthetic rate.