O. C. Taylor

World-wide ambient measurements of peroxyacetyl nitrate (PAN) and implications for plant injury

Abstract Peroxyacetyl nitrate (PAN) is a major phytotoxic component of the photochemical oxidant complex in southern California, but its distribution and effects in other parts of the world are very poorly understood. Based on ambient air sampling at Riverside, California, in 1980, and published reports of PAN concentrations from other parts of the world, PAN concentrations in southern California appear to be five to ten times higher than those reported from eastern North America, western Europe, or Japan. PAN in Riverside, California, averaged 8.1 ppb in July, 9.4 ppb in September and 8.8 ppb in October 1980. These values represent the average of 48 measurements made at 15-min intervals between 0800 and 2000 LT. Potentially phytotoxic episodes, defined herein as PAN > 15 ppb for 4 h during the a.m. period or > 25 ppb for 4h in the p.m. period occurred 27 times in Riverside in 1980. These data were similar to PAN concentrations recorded in the mid 1960s in the Los Angeles Basin, indicating that PAN continues to be a serious air pollution problem in southern California. In contrast, PAN normally averages 1 ppb or less outside of southern California, and because of this low concentration, PAN by itself does not appear to be a major cause of photochemical oxidant injury to vegetation in those regions.

Fluorocarbons in the Los Angeles Basin

Ambient air concentrations of fluorocarbon 11 (fluorotrichloromethane) and fluoro-carbon 12 (dichlorodifluoromethane) have been measured using a gas chro-matograph equipped with a pulsed, electron capture detector. Air samples taken on a moderately smoggy day in July 1970, at several locations near Los Angeles gave average readings of fluorocarbon 12, 0.7 ppb and fluorocarbon 11, 0.56 ppb. These readings were contrasted with those taken in early February 1973 when the air was clear and marked with turbulence due to several seasonal rain storms. The readings of both fluorocarbon 1 1 and 12 averaged about 25% less during clear weather than those taken during moderate smog. The effects of weather conditions on the concentration were also dramatically pointed out by the February samples, in that as much as a tenfold change in concentrations of both fluorocarbons from location to location and from day to day at the same location was observed. A concentration versus altitude study clearly revealed that fluoroca...

The Effect of Light on Predisposing Plants to Ozone and Pan Damage

Experiments were carried out to examine the importance of light as a factor influencing the type and amount of smog damage to plants. The stomatal action of leaves under various light conditions and the correlation of stomatal opening to plant damage from atmospheric pollutants were studied. Results indicated that some other factor than stomates was more important in controlling plant susceptibility to smog. The differences in plant response of various age bean plants suggested that the mechanism of ozone damage is quite different from PAN damage. The relationships between sugar production and ozone damage are examined. 9 references, 11 figures, 2 tables.

Background and vertical atmospheric measurements of fluorocarbon-11 and fluorocarbon-12 over Southern California

Abstract Sample tubes containing air analyzed for fluorocarbon-11 and fluorocarbon-12 were collected in a twin-engined aircraft. The samples were collected at altitudes ranging from ground level to 22000 ft (MSL) over the Southern California area. Background levels of fluorocarbon-11 and fluorocarbon-12 were determined to be 0.060 and 0.090 ppb, respectively. Simultaneous ozone measurements suggest that these fluorocarbons can be used to trace polluted air below the inversion layer.

Effects of air pollutants on apparent photosynthesis and water use by citrus trees.

H Commercially producing lemon and navel orange trees were tested t o determine the effects of ambient air pollutants which occur in the Los Angeles basin on water use (transpiration) and apparent photosynthesis. The entire trees were enclosed in plastic covered greenhouses and were supplied various fractions of the atmosphere to find out whether ozone, peroxyacyl nitrates, or fluorides were causing deleterious effects. Nitric oxide was added t o the air in one treatment to reduce ozone selectively but in so doing, nitrogen dioxide in amounts equal to the ozone was formed. The results showed that the total photochemical smog complex reduced the rate of water use by lemon trees and also reduced the rate of apparent photosynthesis. Fluoride levels occurring in the atmosphere caused no detectable effects. Attempts to evaluate the separate effects of ozone and peroxyacyl nitrates were unsuccessful. Reduction of the ozone in the tree atmospheres by addition of nitric oxide failed t o overcome the reduced water use and lowered apparent photosynthesis.

Air Quality Criteria and Standards for Agriculture

Many food, fiber, forage, and forest crops and a number of animals are adversely affected by a variety of air pollutants. The more important and generally occurring of these pollutants are ethylene, fluorides, ozone, peroxyacyl nitrates (PAN), and sulfur oxides. Their effects upon animals and plants can best be judged by criteria which describe the reaction of biologic materials to pollutant concentration and exposure time. Four criteria are recognized: (1) interference with enzyme systems; (2) change in cellular chemical constituents and physical structure; (3) retardation of growth and reduction in production from altered metabolism; and (4) acute immediate tissue degeneration. Information on tissue degenerative effects due to these pollutants is the most common; there are some reports on growth and productivity reduction; but little data are available on cellular alterations and interference with enzymes. Determination and measurement of the latter two criteria are essential to the ultimate definition ...

APPARENT PHOTOSYNTHESIS AS A MEASURE OF AIR POLLUTION DAMAGE.

A system has been developed to automatically measure the effects of air pollutants in the ambient air on the rate of CO/sub 2/ exchange by intact leaves of citrus trees growing in the field. A miniaturized system utilizing the same nondispersive infrared CO/sub 2/ analyzer has been designed to study individually the effects of different concentrations of air pollutants on photosynthesis and respiration by plants. 16 references, 3 figures.

Ultracytopathological characterization of leaves following short-term exposures of hydrogen chloride gas

Abstract An ultrastructural investigation was conducted to determine the cells and structures in leaves of Phaseolus vulgaris that were affected by short term exposures to gaseous hydrogen chloride. Primary leaf tissues were sampled 24 h after exposure to approx 25 mg HCl m −3 for 20 min. We noted conformational alterations in mitochondria and chloroplasts, cytoplasmic membrane disruption and vesiculation, accumulation of a particulate electron dense material in vacuoles and vesicles, and the elaboration of densely staining globules within fumigated tissues. Most of the severely or totally disrupted cells were confined to the abaxial epidermis.

Phytotoxicity of hydrogen chloride gas with a short-term exposure

Abstract One selected variety from eight species of ornamental plants was used to determine the range of phytotoxic responses to hydrogen chloride gas. Plants of several ages were exposed to varied concentrations of the gas for periods of 20 min each. Injury on exposed plants was evaluated 24 h after completion of exposure and injury symptoms were numerically rated and described. The selected species of plants included aster (Callistephus chinensis), calendula (Calendula officinalis), cornflower (Centaurea cyanus), cosmos (Cosmos, sp.), marigold, American (Tagetes erecta), marigold, French (Tagetes patula), nasturtium (Tropaeolum, sp.), and zinnia (Zinnia angustifolia). Of these, cosmos and both marigolds appeared to be the most sensitive to HC1. Plant injury estimated at the 10% level was caused by 20 min exposure to 6.5 and 8.7 mg HCl m−3 ∗ .

Significance of Atmospheric Ozone as a Phytotoxicant

Since the recognition of ozone as a major phytotoxicant in crop plants in 1957, ozone type symptoms have been observed in a wide range of vegetation. These observations include leafy vegetables, field, forage, and textile crops, also shrubs, broad-leafed ornamental, fruit and forest trees, and various conifers. Fumigation experiments at various institutions have confirmed the etiological relation of ozone in many of these observations. Such visible injuries fail to provide a reliable index to the damaging impact of ozone on the numerous plants affected. Hidden injury or damage by ozone at sub-necrotic levels has been reported and experimentally established in a number of crop plants. Evidence is available which indicats that citrus varieties are so affected, and that much of the citrus decline in Southern California may be ozone induced. Photochemically induced ozone may prove to be the most persistent, if not the most difficult, of atmospheric phytotoxicants to control. Ozone type injury has been reporte...Since the recognition of ozone as a major phytotoxicant in crop plants in 1957, ozone type symptoms have been observed in a wide range of vegetation. These observations include leafy vegetables, field, forage, and textile crops, also shrubs, broad-leafed ornamental, fruit and forest trees, and various conifers. Fumigation experiments at various institutions have confirmed the etiological relation of ozone in many of these observations. Such visible injuries fail to provide a reliable index to the damaging impact of ozone on the numerous plants affected. Hidden injury or damage by ozone at sub-necrotic levels has been reported and experimentally established in a number of crop plants. Evidence is available which indicats that citrus varieties are so affected, and that much of the citrus decline in Southern California may be ozone induced. Photochemically induced ozone may prove to be the most persistent, if not the most difficult, of atmospheric phytotoxicants to control. Ozone type injury has been reporte...