Walter W. Heck

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)

Ozone: Nonlinear Relation of Dose and Injury in Plants

Ozone produces a sigmoidal dose-injury response in sensitive tobacco and pinto bean. A definite threshold concentration and presentation time are required before injury is initiated.

Interactions of environmental factors on the sensitivity of plants to air pollution

Before potential damage to vegetation can be adequately forecast, even after an air pollution alert has been placed in effect, a clear understanding of the interactions of environment on plant sensitivity must be ascertained. This involves detailed study of single factors and then multiple factors using the phytotoxicants in question. Factors studied or suggested include light (quality, intensity, and duration), temperature, carbon dioxide concentration, humidity, wind, soil moisture, soil aeration, nutrient levels, and soil texture. This paper presents a review of the work relating plant injury to specific air pollutants as conditioned by several environmental conditions supported by research on the interactions of ozone with these environmental conditions.

The Effects Of Ozone On Tobacco And Pinto Bean as Conditioned by Several Ecological Factors

The sensitivity of tobacco and/or pinto bean to ozone, as an air pollutant, is increased by growing plants in a shortened photoperiod under reduced light intensity and in a light potting mix. Sensi...

Effects of acute ozone exposures on snap bean at various stages of its life cycle

Abstract Snap beans ( Phaseolus vulgaris L. ‘BBL-290’) were exposed to ozone (O 3 ) at 0 (carbon-filtered air), 30 and 60 pphm for two 1.5 h periods that were 3 days apart. Plants were exposed to O 3 at six different stages (8+11, 14+17, 20+23, 26+29, 32+35, or 38+41 days after seeding). Half of the plants were harvested 7 days after the second exposure and the other half were harvested 48 days after planting. Ozone reduced relative growth rate, absolute growth rate, pod production, nodulation, and total nitrogen content, but increased the amount of nitrogen per gram of plant tissue. The magnitude of these responses of growth, nodulation and nitrogen content varied with the O 3 concentration and plant age at the time of exposure. Recovery of growth and nodulation at the final harvest was partial for plants exposed at 8+11 and 14+17 days. Nitrogen content was correlated with both plant dry weight (root + top dry wt; r 2 = 0.95) and nodule number ( r 2 = 0.93). These relationships were described by exponential equations.

An Air Quality Data Analysis System for Interrelating Effects, Standards, and Needed Source Reductions: Part 3. Vegetation Injury

Acute leaf injury data are analyzed for 19 plant species exposed to ozone or sulfur dioxide. The data can be depicted by a new leaf injury mathematical model with two characteristics: (1) a constant percentage of leaf surface is injured by an air pollutant concentration that is inversely proportional to exposure duration raised to an exponent; (2) for a given exposure duration, the percent leaf injury as a function of pollutant concentration tends to fit a lognormal frequency distribution. Leaf injury as a function of laboratory exposure duration is modeled and compared with ambient air pollutant concentration measurements for various averaging times to determine which exposure durations are probably most important for setting ambient air quality standards to prevent or reduce visible leaf injury. The 8 hour average appears to be most important for most of the plants investigated for most sites, 1 hr concentrations are important for most plants at a few sites, and 3 hr S02 concentrations are important for...

Nature, Extent, and Variation of Plant Response to Air Pollutants

Publisher Summary The investigations of air pollution injury to vegetation began near the middle of the 19 th century. Injury from leaking illuminating gas mains also was an early problem. Ethylene was identified as the toxicant in the illuminating gas. The complete loss of vegetation may be avoided in the future, but interest in the problem has continued, primarily because of the increased number of large power plants that burn sulfur-containing fuels and emit high concentrations of sulfur oxides. This chapter identifies the major air pollutants and discusses the nature and extent of air pollution problems. It also describes the symptoms of injury caused by these pollutants, especially on crop plants. Air pollution problems have increased because of multiple sources and mixtures of pollutants. There is increased concern about chronic injury and reduced growth attributed to air pollutants such as photochemical oxidants and sulfur oxides. The response to pollutants may be altered by many factors such as genetic, environmental, cultural conditions, time-concentration relationships, and the presence of mixtures of pollutants. The identification and use of tolerant varieties, including resistant varieties developed by breeding, will help reduce losses and assure maximum agricultural production.

Response of Bean and Tobacco to Ozone: Effect of Light Intensity, Temperature and Relative Humidity

Pinto bean (Phaseolus vulgaris, L.) and Bel W3 tobacco (Nicotiana tabacum, L.) were grown and exposed to 40 pphm ozone for 1 hr under a range of light intensities, temperatures, and relative humidities. Foliar injury to the more sensitive plant leaves was determined on the third day after exposure. Each atmospheric factor was independently assessed. Two significant three-way interactions were found: exposure light intensity by growth light intensity by species, and growth temperature by exposure temperature by species. Three significant two-way interactions were found for humidity: growth humidity by exposure humidity, growth humidity by species, and exposure humidity by species. The sensitivity of each species to ozone changed with changes in each environmental condition.

Response of soluble sugars and starch in field-grown cotton to ozone, water stress, and their combination

Abstract Ozone (O3) stress is known to reduce the growth and yield of a number of crops, and water stress can modify the extent of these effects. Both O3 and water stress alter the carbohydrate status of plants. Little is known, however, concerning O3 effects on carbohydrate pools of field-grown plants and whether water stress will modify the carbohydrate response to O3. Cotton (Gossypium hirsutum L. “McNair-235”) plants were exposed to five O3 concentrations in open-top field chambers for 12 hr/day throughout the growing season at two levels of soil water (well-watered or periodically water-stressed). The O3 concentrations ranged from 0.021 to 0.073 μl/l (seasonal mean 12 hr/day concentration). Plants were sampled from each plot on four occasions encompassing the early- to late-reproductive stages of growth. Soluble sugars (glucose, fructose and sucrose) and starch were measured in leaves, stems and roots at each sampling date. Analysis of variance was performed for main effects and interactions of O3 and water treatments at each sampling date (O3 effects were partitioned in linear and quadratic components). Effects of O3 and water stress on soluble carbohydrates and starch were most common in stems and roots. Ozone suppressed carbohydrate concentrations in all cases where significant O3 effects were detected in the absence of O3 × water interactions. On the other hand, soluble carbohydrate concentrations were greater in water-stressed plant tissues when effects were significant and in the absence of interactions. Water-stress effects on starch were variable. Interactions of O3 and water stress were not consistent but often included interaction with the quadratic O3 component.

ENVIRONMENTAL CONDITIONS AFFECTING THE USE OF PLANTS AS INDICATORS OF AIR POLLUTION.

The present study was initiated to determine the effect of stomatal opening, soil, and nutrient level on the sensitivity of plants to photochemical air pollutants. Pinto bean and tobacco were used at test plants. Results indicate that the degree of plant damage can be reduced by controlling the soils, nutrient, and water requirements of plants.