Hugo H. Rogers

A field technique for the study of plant responses to elevated carbon dioxide concentrations

Field techniques that would permit the study of elevated CO/sub 2/ levels on plants are described. The design, construction, and testing of a system for dispensing and monitoring CO/sub 2/ in the number of open top chambers are discussed. (JMT)

Response of agronomic and forest species to elevated atmospheric carbon dioxide

The effects of atmospheric carbon dioxide on corn, soybeans, loblolly pine, and sweetgum were studied in the field during a growing season. The plants were exposed to a range of concentrations of carbon dioxide day and night in open-topped, flow-through chambers. At a mean daytime carbon dioxide concentration of 910 parts per million, increases in total biomass ranged from 157 to 186 percent of the control values. Seed yield and wood volume increased and there were changes in plant anatomy and form. Net photosynthesis increased with increasing carbon dioxide concentration in soybeans and sweetgum, but was unaffected in corn. Water use efficiency also increased in corn, soybeans, and sweetgum.

Nitrogen-15 Dioxide Uptake and Incorporation by Phaseolus vulgaris (L.)

The sorption rate and metabolic fate of nitrogen dioxide, a major air pollutant, have been determined for Phaseolus vulgaris (L.). Sorption was determined kinetically by chemiluminescent monitoring of 15NO2 removal from the test atmosphere and directly by mass spectrometric analysis of nitrogen derived from the plant tissue. Sorptive processes were first order with respect to 15NO2 concentration. Virtually all of the 15NO2 taken up was metabolized.

Uptake of atmospheric ammonia by selected plant species.

Abstract Rates of NH 3 uptake were measured for 10 crop species by direct kinetic techniques. A continuous stirred tank reactor (CSTR) system designed for plant gas exchange studies was used in the NH 3 exposures. Ammonia was monitored with an analyzer that permitted real time measurement of atmospheric NH 3 down to 5 ppb. This permitted measurement of dynamic sorption of NH 3 at concentrations much closer to ambient levels than previously reported. Uptake rates increased with increasing light, temperature, and NH 3 concentration. An inverse correlation was observed between total diffusion resistance of leaves and NH 3 sorption. Rates did not vary significantly with repeated exposure or with changes in growth media N.

Estimation of leaf area of soybeans grown under elevated carbon dioxide levels

Abstract Leaf area (LA) data are required for describing numerous canopy processes. However, determining LA for a crop is both time consuming and labor intensive, requiring a substantial investment of resources. The objectives of this study were (1) to develop statistical models for estimating LA of field-grown soybean ( Glycine max ) plants grown in open-top field chambers from measurements of destructive (leaf and top dry weight) and non-destructive (leaf number, plant height, and branch length) variables, (2) to examine the effect of CO 2 concentration on these statistical relationships, and (3) to test the applicability of such models to independent data collected under different experimental conditions. Predictive models of LA based on either branch length (LA = 147.6· BRL 0·635 , CV = 11%) or top dry weight (LA = 328.8·TDW 0·731 , CV = 12%) were found to have the lowest coefficient of variation about the regression line, to be unaffected by increasing CO 2 , and to be reasonable predictors of LA under different growth conditions. Both leaf area per leaf and specific leaf area ratios changed with increasing CO 2 and growth conditions. Plant height was a poor predictor of LA.

Dry deposition of ammonia at environmental concentrations on selected plant species

The deposition velocity of NH/sub 3/ on six plant species at environmental concentrations has been studied in a dynamic plant gas exchange reactor. The total resistance to the transport of NH/sub 3/ was studied. The aerodynamic resistance was determined directly by NH/sub 3/ gas absorption in aqueous solutions at environmental concentrations in a two-phase gradientless reactor modeling the transfer processes through the stomata in a leaf. The concentration of NH/sub 3/ in the gas phase ranged from 50 to 1000 ppb and the temperature varied from 25 to 30/sup 0/C. The results for the deposition velocity for NH/sub 3/, during the day, varied from 0.3 to 1.3 cm/s. The deposition velocities at night were about one order of magnitude smaller. These results are compared with estimates from the Froessling equation which consistently yields higher values of the same order of magnitude. To determine accurate atmospheric transport models or global budget models, a variable deposition velocity should be used to account for the diurnal and seasonal variations in the surface resistance.

Dynamic atmospheric chamber systems: applications to trace gas emissions from soil and plant uptake

Atmospheric emissions, transport, transformation and deposition of trace gases may be simulated through chambers. The dynamic flow-through chamber system has been developed in response to a need to measure emissions of nitrogen, sulphur and carbon compounds for a variety of field applications. Oxides of nitrogen (NO, NO2, NOY) emissions have been measured from agricultural fertilised/unfertilised soils. Ammonia-nitrogen (NH3–N) and reduced organic sulphur compound emissions have been measured using this same technique across a gas-liquid and soil-atmosphere interface at swine waste treatment anaerobic storage lagoons and in agricultural fields. Similar chamber systems have also been deployed to measure the uptake of nitrogen, sulphur, ozone and hydrogen peroxide gases by crops and vegetation to examine atmospheric-biospheric interactions. Emission measurements compare well with a coupled gas-liquid transfer with chemical reaction model as well as a US Environmental Protection Agency (EPA) WATER9 model.