NO. 17 INHIBITION OF PLANT GROWTH — WEINTRAUB AND PRICE 5 



zett and Woodcock, 1910, 1912). It has been demonstrated, further, 

 that oxidation of various fats and fatty acids results in development 

 of antibiotic activity ^ ( Sabalitschka, 1939; Spoehr et al., 1945, 1946) 

 and that in some instances such activity is due to volatile substances 

 (Harris, Bunker, and Milas, 1932a, b) ; the reputed sanitary value 

 of oil paints has been ascribed to production of volatile aldehydes 

 (Gardner, 1914b; Hewitt, 1943). The vapors of a number of essen- 

 tial oils, too, have been found to be bactericidal or bacteriostatic 

 (Schobl and Kusama, 1924; Schobl, 1925). 



On the other hand, some w^orkers have ascribed the antibiotic effects 

 which accompany oxidation of oils to emission of radiant energy 

 (Wrenn, 1927; Ried, 1930). 



Radiation versus chemical vapor. — In order to determine whether 

 the growth inhibition of seedlings caused by wood is due to a vapor 

 or to radiant energy emitted by the wood, th^ following experiments 

 were performed. 



In a metal box containing a few small boards were placed two 

 dishes of seeds, one of which was in turn enclosed in a cell with 

 2.1-mm. thick windows of Corning No. 791 glass. According to the 

 manufacturer, this glass transmits ultraviolet radiation of wave lengths 

 greater than 2200 A. The plants exposed directly to the wood were 

 strongly inhibited while those within the cell, which were protected 

 from any chemical vapor arising from the wood, all developed nor- 

 mally (pi. 6, fig. i). This experiment demonstrates that no apprecia- 

 ble part of the inhibition by wood can be due to radiation of wave 

 lengths greater than about 2200 A., although it does not eliminate the 

 possibility of activity by shorter wave lengths. 



In the second test, dishes of seeds were placed in two similar 1.5- 

 liter bell jars which were connected separately to a compressed-air 

 line. Humidified air was blown through each jar at about 15 liters 

 per hour, the air being directed onto the seeds by means of an in- 

 verted glass funnel situated immediately above them. The air supply 

 to one jar was first passed through a metal can containing seven 

 small pieces of board (total weight = 770 g.). The plants exposed 

 to air which had been in contact with the wood were markedly in- 

 hibited (pi. 6, fig. 2) indicating that the active agent had passed from 

 the wood-containing can to the bell jar. As these were connected by 

 a 40-cm. length of small-bore rubber tubing bent in a semicircle, the 

 conclusion seems inescapable that the inhibitory agent was trans- 

 mitted as vapor rather than as radiant energy. 



6 Antibiosis is here employed in its broadest sense of an action inimical to 

 normal life processes. 



