The Effects of Illuminating Gas on Root Systems

Abstract

1. When illuminating gas is passed through soil, the odor-giving constituents of the gas are readily absorbed by the soil particles and strongly held. 2. These odorous substances are very slightly, if at all, toxic to roots of plants growing in a soil containing them. 3. The constituents of illuminating gas which remain in a gaseous state in the soil interstices are the chief cause of injury to root systems. 4. Among these constituents, ethylene is probably the most harmful, except in extremely high concentrations of illuminating gas, where the toxicity of other substances, together with other factors, would be expected to play a part. 5. Low concentrations of gas induce abnormal development of tissue. a) Illuminating gas.-These abnormalities appear in certain tree seedlings within 8-21 days, with concentration one part illuminating gas to four parts air (air of the soil), or as low as one part illuminating gas to forty of air. b) Ethylene.-This gas alone, when used in concentrations corresponding to the ethylene content of the illuminating gas used in the tests, gives abnormalities similar in type and degree. 6. High concentrations of illuminating gas result in the rapid killing of the roots, and the only symptom of injury to be observed is death. 7. If illuminating gas is allowed to flow very slowly through a soil in which woody plants are growing, abnormal tissue development in the root will very often ensue. 8. In low concentrations of illuminating gas, hydrolysis of starch and some other related chemical reactions are accelerated. 9. It was found that, by use of the etiolated sweet pea seedling, small amounts of illuminating gas in the soil could be detected where the odor of gas was indistinguishable by the usual methods.