Fluctuations in Sensitivity of the Avena Test Due to Air Pollutants

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A daily and seasonal fluctuation in sensitivity of the Avena test to given concentrations of applied auxin is well known. It was found that in filtered and unfiltered air, the durnal fluctuation which occurred in plants grown in unfiltered air was absent in those grown in filtered air, indicating that the variation in sensitivity was a function of fluctuations in concentrations of air pollutants.

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It appears from the preceding chapters of this volume that growth under almost all circumstances is more or less intimately connected with metabolism. One experimental difficulty in studies of growth is to discern conditions directly, or more or less directly, affecting growth from those connected with metabolism not specifically essential for growth. This also holds true with regard to chemical growth factors. — Let us consider a unicellular bacterium or an alga. Its growth depends upon the external supply of different organic and inorganic compounds. According to the prevailing conditions sometimes one, sometimes another is deficient, thus becoming the chemical factor limiting growth. Together they form a heterogeneous set of chemical growth factors with varying modes of action.
The plant in innumerable chemical ways controls its own development from germination to flowering and the ripening of fruits and seeds. These chemical controls are “self„ controls as certain substances, like growth hormones, germination inhibitors etc., produced by the plant body itself, regulate the physiological functions of this self-same body.
In diesem Bericht sind die Veröffentlichungen aus den Jahren 1953 und 1954 zusammengefaßt, die sich mit genetischen und genphysiologischen Fragen befassen. In einzelnen Fällen war es zum Verständnis der neueren Untersuchungen notwendig, auf ältere Arbeiten zurückzugreifen, die in den vorigen Referaten nicht berücksichtigt wurden. Die Gewichtsverteilung auf wenige, im Mittelpunkt der Diskussion stehende Probleme hat sich nur geringfügig verändert. Um die Orientierung zu erleichtern und den Anschluß an die früheren Berichte zu wahren, wurde daher im wesentlichen die Reihenfolge der Abschnitte aus den letzten Bänden beibehalten.
Phytotoxic effects of air pollutants are well known. In experiments with relatively higher concentration of pollutants, reduction in plant growth and productivity and visible injuries such as chlorosis and necrosis have been frequently observed. However, in the ambient atmosphere, air pollutants exist at low concentrations and at these concentration they may not induce any visible damage, although they may interefere with several metabolic or enzymic activities of the plants (Srivastava, 1978). Since hormones play an important role in growth and differentiation of plants and they also modify metabolic or enzymic activities, very often the effects of air pollutants on plants are interpreted in terms of changes in hormonal metabolism. In addition, applicalion of exogenous hormones modifies the effects of air pollutants on plants by interferring with the normal growth and metabolism. The present review relates to these interactions of air pollutants and hormones.
With the improvements in instrumentation and the application of more and more precise chemical and physical methods in the physiological analysis of plants, the uniformity of the experimental material usually becomes the limiting factor in experiments with plants. This aspect of experimental procedure has not received the attention of Botanists it deserves. It has been shortly discussed in Kostyschew-Went (1931) on pp. 301–303.
The physical environment in which plants generally grow and develop is not constant. There are fluctuations in the environment, many of which do not occur solely as random or sporadic events. Rather, these changes appear at regular and predictable intervals. For example, each day as the earth rotates on its axis, plants growing out of doors are subjected to alternating spans of light and darkness. Furthermore, depending on the season of the year, the duration of each span changes predictably in relation to the inclination of the planetary axis. This single feature of solar radiation involving the lengths of light and dark spans is but one of many physical events that occur in rhythmic cycles.
Raphanus sativus L. cv. Cavalier (radish) plants were sprayed with 30 mg/l concentration of each of 4 growth regulators, and fumigated with ozone at a concentration of 25 parts per hundred million for 4 h. Plants treated with the growth regulators responded to ozone in different directions and with varying magnitudes. Overall, N6-benzyladenine was the most active in terms of the protection of plants from oxidant damage. This was followed by indole-3-acetic acid and gibberellic acid. 2-chloroethylphosphonic acid accentuated phytotoxicity as well as root (radish) weight reduction.
Air pollution damage to vegetation has been recognized for more than a century. In this paper the occurrence and distribution of photochemical air pollution are described. Enumerated are some of the raw materials and products of these oxidation systems responsible for plant damage. The biochemical, physiological, and pathological effects of these contaminants on plants were indicated. The development of standards for ambient air quality are essential for the conservation of air as a limited natural resource and the protection of our agricultural economy through the prevention of photochemical air pollution damage to plants. 62 references.
The role of auxin in the recovery of plant tissue from oxidant treatment was investigated. Treatment of oat coleoptile sections with concentrations of indoleacetic acid (IAA) or 2,4-dichlorophenoxyacetic acid (2,4-D) optimal for normal growth, following pretreatment with moderately inhibiting levels of peroxyacetyl nitrate (PAN) immediately accelerated recovery of growth rate. In some cases inhibition was also less at supraoptimal values of auxin. Treatment of ozonepretreated tissue with IAA or 2,4-D enhanced inhibition at high levels of auxin and produced an optimal growth concentration level which was lower than for sections not given ozone pretreatment. Auxin treatment also reduced the degree of inhibition in fluoride and iodoacetamide-pretreated sections. Mechanisms by which auxin-induced recovery from inhibition may occur are discussed.
1. In the Avena-test the curvatures produced by auxin can be considerably increased by ether-vapour. 2. The effect is optimal in the daylight test (Söding 1952) when water saturated with ether to about 25% is placed next to the seedlings in a separate beaker under a glass cylinder (Fig. 1). 3. The curvature produced by auxin is increased by the ether vapour over the whole length of the curved zone. In plants treated with ether the curvature extends about 1 mm farther towards the base of the coleoptile. 4. The increase of the curvature is caused by a temporary stimulation of growth by the ether vapour. Thus the temporary stimulation of growth by low concentrations of ether demonstrated by Schroeder as early as 1908 has been confirmed with the Avena-cylinder-test.
SAMPLES of human urine have been examined for indole and phenol acids as a matter of routine in this laboratory for several months; the methods used for extraction and two-dimensional paper chromatography were described earlier1,2. The chromatograms were satisfactory until certain days in April, when the normally pink and purple spots given by indoles with p-dimethylaminobenzaldehyde showed a diminished colour intensity and brown discoloration. The colours became so weak in May that indole spots could not be seen with certainty. Unlike the indoles, the phenolic acids gave colours which were normal immediately after spraying with diazotized sulphanilic acid, but which faded and were discoloured afterwards to an increasing extent. No improvement was obtained when the components of the chromatographic solvents were purified extensively.
Emissions from motor vehicles are now known to be the principal source of the raw materials contributing to photochemical air pollution in California. Some of the products of the reaction, ozone, peroxyacyl nitrates, and the unidentified products of ozone-olefin reactions, are very damaging to the leaves of a variety of crop plants. The injury that was once confined to Los Angeles County now occurs in many states and causes economic loss estimated in excess of $25,000,000 annually. Ethylene, one of the compounds found in the exhaust, is also very injurious to several crops. The ability of a given toxicant to incite injury is dependent on the age of the leaf and the conditions of illumination under which the plant is grown prior to, during, and after fumigation. In addition, the growth of plants, even in the absence of visible injury, is materially affected. Evidence is presented to indicate that the chemical and physical systems within the plant are disrupted by the phytotoxicants.
Avena coleoptile sections incubated in solutions through which photochemically produced oxidant mixtures, ozone or peroxyacetyl nitrate (PAN) are passed, display subsequent repressed growth in fresh solutions to which auxin has been supplied. Treatment by oxidant recording as 1.4 ppm derived from an irradiated mixture of trans-2-butene and NO/sub 2/ results in about 50% inhibition of elongation. About 1.5 ppm PAN also inhibits growth to the same degree or more. Approximately 170 ppm ozone produced comparable magnitudes of inhibition. In all cases basal respiration was inhibited little or not at all.
Aqueous solutions of indole-3-acetic acid are inactivated by standing for a variable period of time. Inactivation results from conversion by oxidation of the plant hormone to polymerized deuterauxin, which is depolymerized by boiling of the solution, which restores activity.
Zusammenfassung Es wurde die Wirkung einer Standardlösung von β-Indolyl-Essigsäure auf dieAvena-Koleoptile mittels der in Kopenhagen verwendeten Wuchsstoffbestimmungsmethode untersucht. Die Schwankungen der Krümmungsgröße von Tag zu Tag betrugen in zwei Versuchsreihen nur etwa 35%.
The established phytotoxic agents of air pollution, such as SO2 and fluorine, are not the primary constituents causing plant damage in the air pollution of this area. The initial injury in most cases is in the lower mesophyll. Leaves of crop plants which have little or no pubescence and a moderate amount of cuticle develop a shiny, glazed appearance. Pubescent leaves having little or no cuticle appear somewhat bleached and lack the metallic luster. Subsequently extensive necrotic areas develop. As a result of a survey of 11 susceptible crops in 1949 in Los Angeles County, it is estimated that the aggregate loss due to smog injury was nearly $500,000. || ABSTRACT AUTHORS: G. K. Parris
Spinach, beet, endive, oat, and alfalfa plants were used for the determination of crop damaging pollutants in the air of metropolitan Los Angeles. The catalytic oxidation of the olefins with NO/sub 2/ under the influence of sunlight produces oxidation products very similar to those produced by ozone. In the plant fumigations with oxidation products of olefins, lachrymatory effects were often observed. These investigations demonstrate the utility of plants in analyzing air pollutants. They further show for the first time that hydrocarbons, normally harmless air pollutants of organic nature, can cause severe damage through their reaction with substances know to be in the air. In this way these experiments have contributed to a better understanding of the smog problem.
The effect of synthetic smog (1-n-hexene plus ozone) on growth and transpiration of tomato plants (Lycopersicon esculentum) and on elongation of etiolated pea sections (Pisum sativum) has been studied. Use has been made of hidden damage (growth decrease in the absence of visible injury) to measure the effect of light, sucrose spray, ..beta..-naphthoxyacetic acid, and water supply on smog injury. Growth of tomato plants fumigated in the dark or light just following a 12-hour dark period or in the dark after one and one half hours of light was unaffected by smog. Growth of plants fumigated in the light at mid-day or early afternoon was signficantly decreased by smog treatment. Sucrose spray partially protected tomato plants against smog damage. ..beta..-naphthoxyacetic acid did not significantly affect the response of tomato plants to smog. Smog treatment did not affect the elongation of etiolated pea sections either in water or in 2,4-D solution. Tomato plants given limited water supply were resistant to smog damage while comparable plants receiving ample water were susceptible. Transpiration and water uptake rates of tomato plants were decreased by subjection to smog. The decrease was followed by recovery to slightly less than control rates. Subsequent fumigation caused repeated drops in transpiration rates followed by partial recovery. No direct correlation between stomatal opening and response of plants to smog was observed.
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