Laurence I. Heller

Effects of acidity of simulated rain and its joint action with ambient ozone on measures of biomass and yield in soybean

Abstract An experiment was performed to determine whether the presence of ozone modified the effects of acidity of simulated rain on growth and yield of soybean ( Glycine max. [L.] Merr.). Beeson, a type II cultivar, was grown in field chambers and exposed to simulated rain at 3 levels of acidity, pH 4.0, 3.4 and 2.8. Each level of acidity was applied to plants grown either in unfiltered ambient air or in charcoal filtered (to remove ozone) ambient air. An interaction between acidity of simulated rain and filtration of ambient air on growth and yield was present. The difference in total dry mass between plants grown in filtered and unfiltered chambers increased with increased acidity, of simulated rain treatments. In filtered air, vegetative mass was only slightly decreased with increased acidity, whereas reproductive mass was increased with increased acidity. In unfiltered air vegetative mass decreased with increased acidity but reproductive mass was only slightly decreased at pH 2.8. Components of yield also were differentially affected by acidity, which indicates the need for a better understanding of the sensitivities of different development processes of the plant to each kind of pollutant. The apparent interaction between ozone and acidic rain indicates that further investigations on this combination must be conducted before acidic rain effects on plant growth can be accurately assessed in ambient atmospheres.

A Simple, Rapid Potentiometric Method for the Estimation of Fluoride in Vegetation

Abstract A new method for the estimation of fluoride in vegetation has been developed. The technique employs a selective ion electrode for measurement of fluoride obtained by acid extraction from pulverized plant tissue. This potentiometric method is simple and rapid and provides results which correlate with those obtained by established methods.

Phenology and cold tolerance of Picea rubens sarg. Seedlings exposed to sulfuric and nitric acid mist

During the growing seasons of 1985–88, red spruce (Picea rubens Sarg.) seedlings were exposed repeatedly in field chambers to sulfuric and/or nitric acid mist in the range of pH 2.5 to 4.5. Hydrogen ion, sulfate, and nitrate concentrations in mist were within the range found in cloudwater of the northeastern USA where high‐elevation spruce forests are declining. After the period of exposures, seedlings remained outdoors and buds were sampled in the autumn to determine effects of mist treatments on the number of developing needle primordia. Current‐year foliage was sampled from autumn to spring for measurement of cold tolerance by freeze‐induced electrolyte leakage (FIEL) and buds were scored for degree of bud break in the early spring. In the 1985–87 experiments when 16‐hour overnight mist events were continuous, there were few statistically significant effects of acidic mist on needle primodia development, foliar FIEL, and bud‐break. However, in the 1988 experiment when 16‐hour overnight mist events were...

Effects of simulated acidic rain applied alone and in combination with ambient rain on growth and yield of field-grown snap bean

Abstract Field-grown snap bean (Phaseolus vulgaris L. cultivar ‘Provider’) plants were treated with simulated acidic rain applied either alone or in combination with ambient rain and the effects on growth and yield were determined. In plots where ambient rain was excluded, a retractable canopy was activated to shield the crop. Four levels of acidity at pH values of 5.0, 4.2, 3.4 and 2.6 were applied in four replicate treatments and the experiment was conducted in two successive years (1981 and 1982). In plots that received only simulated rain, yield was not adversely affected by acidic rain; in 1981, a positive linear relationship was present between acidity of simulated rain and yield, but in 1982, no effect was found. In contrast, in plots that received both simulated and ambient rain, a negative linear relationship between acidity in simulated rain and yield was observed in both years. Changes in yield were due to effects on the number of pods per plant. Vegetative mass and size of pods were unaffected by acidity in simulated rain in either experimental condition. Apparently, acidic rain has no detrimental effect on growth or yield of snap bean, especially under conditions of normal water supply. Plant response to acidic rain, however, was altered by the presence of ambient rain. Consequently, previous research performed without exclusion of ambient rain should be re-evaluated, and current research should provide for control of water supply as well as deposition of hydrogen ions and other components in rain.

Effect of fertilizer on the growth of radish plants exposed to simulated acidic rain containing different sulfate to nitrate ratios.

Two successive experiments were performed in the greenhouse to test the hypothesis that plant response to the amounts and ratios of sulfuric and nitric acids in rain is affected by the amount of fertilizer added to the growing medium. Radish plants, grown with different levels of N?P?K fertilizer, were given ten 1-h exposures over a 3-week period to simulate acidic rain at pH values from 2.6 to 5.0 and sulfate to nitrate mass ratios from 0.3 to 7.5. Increased acidity of simulated rain reduced plant growth, with a greater depression of hypocotyl mass than shoot mass. The reverse growth response occurred with increased supply of fertilizer: plant biomass rose with a larger increase in shoot mass than hypocotyl mass. In one experiment, plants that received a greater supply of fertilizer exhibited more obvious reductions in growth of hoots at the higher levels of acidity of simulated rain. There were no significant effects of sulfate to nitrate ratios in simulated rain on plant growth, nor any effect of this ratio on the response of shoots and hypocotyls to acidity of simulated rain. Addition of fertilizer had no effect on plant response to sulfate to nitrate ratios. These results do not support the hypothesis that nutrient-deficient plants are either more or less responsive to sulfate and nitrate in rain than plants grown with optimal supplies of nutrients. They support previous results indicating no effects of sulfate to nitrate ratio in simulated acidic rain on plant growth. The results also suggest that the greatest risk of harmful effects on vegetation may come from the combination of high sulfate and high acidity in rainfall.