124 PLANT GROWTH SUBSTANCES 



In many studies of auxin-controlled curvatures the Avena coleoptile 

 has been used as the standard experimental material. Therefore, this 

 discussion is to analyze the inherent electrical pattern, as a possible 

 correlation mechanism, of the same plant. For convenience of organiza- 

 tion this paper will be divided into the three following parts: examination 

 of the bioelectrical pattern of the nonstimulated coleoptile; changes of 

 certain components of the electrical field that result from stimulation 

 by different types of energy; effects of altering the inherent electrical 

 field by superimposing an electrical polarity of external origin. 



The Electrical Field of the Nonstimulated Coleoptile 



By performing a large number of experiments in which every possible 

 precaution was taken to keep all of the environmental factors constant, 

 Wilks was able to work out the distribution of electrical potentials of 

 the Avena coleoptile in considerable detail (39). His observations were 

 completely confirmed and extended by Schrank during the course of a 

 later investigation (27). The results of these many experiments can be 

 briefly summarized by the use of a diagram, which shows the dimensions 

 of the electrical pattern quite distinctly. In presenting the diagram, 

 shown in Figure i, a few explanatory remarks should be included. First, 

 it is important to remember that one of the general characteristics of 

 electrical polarities of living systems is that they vary quite appreciably 

 from one instant to the next, even though a source of stimulation is not 

 apparent (39). It is not uncommon for the longitudinal electrical polarity 

 of an intact Avena coleoptile to change from 10 to 20 millivolts during 

 the course of ten minutes. Second, the magnitude of a given polarity is 

 not necessarily the same in all plants which are otherwise similar. These 

 circumstances naturally demand that the magnitudes of the voltages 

 expressed in the figure are only approximate averages. 



Examination of Figure i reveals several relevant points to which 

 attention should be directed. In so far as the external longitudinal 

 electrical polarity is concerned (circuits labeled X, Y, and Z), it becomes 

 apparent that the apical region is electronegative to the base; the magni- 

 tude of the polarity is of the order of about 50 millivolts. The most 

 negative region, with respect to the base, is the section about 5 to 8 

 millimeters below the apex. This also appears to be the region of the 

 greatest radial polarity (circuits L, M, N, O, and P). It is noted that the 

 orientation of the radial polarities of the apical 17 millimeters is such 



