CHAPTER 4 



Physiological Effects of Ethylene and Other 

 Unsaturated Carbon-containing Gases 



Early Experiments 



Beginning at the University of Chicago and continuing later at Boyce 

 Thompson Institute in a much more detailed way, a group of investigators 

 have made extensive studies of the effects of gases upon plants. In the 

 later phases, the researches were extended to the effect of some of the gases 

 upon animals. In regard to the physiological effect of the gases upon 

 plants we may speak of two groups: (1) gases low in lethal action and high 

 in anesthetic and growth-modifying effects, among which are certain un- 

 saturated C-containing gases such as ethylene, acetylene, propylene, and 

 carbon monoxide; (2) gases mainly lethal that have only minor physio- 

 logical action other^^ise, including hydrocyanic acid, mercury vapor, 

 sulfur dioxide, ammonia, chlorine, and hydrogen sulfide. The physiologi- 

 cally active gases will be discussed in this chapter and the lethal gases in 

 the follo\\ing chapter. 



This work was initiated by a question from a Polish greenhouse operator, 

 a good grower but painfully short on English, "What is the effect of illumi- 

 nating gas on carnations?" Answering his question raised others; as a 

 result, much of the w^ork reported in this and the two chapters that follow 

 was an outgrowth of his question. Since the hormone work at the Institute 

 originated in the anesthetic and formative effects of ethylene upon plants, 

 all the work reported in the hormone chapter is a continuation of the 

 answer to the Polish greenhouse operator's query. The author has been 

 assigned two botany problems in his time. One was the reason for the dif- 

 ference in behavior of the two seeds in the cocklebur, assigned by Professor 

 Chas. F. Hottes of the University of Illinois (1902), and the other was the 

 illuminating gas problem (1908) here discussed. The previous two chapters 

 show what has come of the first assignment, and this and the next two 

 chapters set forth the results of the second. Each, of course, has involved 

 the cooperation of a number of investigators, not only in the laboratories 

 with wliich the author has been associated, but in laboratories throughout 

 the world. The literature on the remarkable physiological effects of the 

 unsaturated C-gases has become almost voluminous smce 1908, though 

 most of it has appeared since 1930; only a portion can be cited in this 

 popular discussion. Which assigned the better problem, the learned uni- 

 versity professor or the practical greenhouse operator, quite innocent of 

 higher learning? 



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