\H A. B. Plowman — Electromotive Force in Plants. 



Art. YIII. — Electromotive Force in Plants ; by Amon 



B. Plowman. 



Every disturbance of the atomic relations within any 

 material body is, in all probability, attended by a more or 

 less pronounced electrical disturbance in the ether surrounding 

 the atom. Whether or not this condition of electrical stress 

 can be detected depends upon the amplitude of the atomic 

 displacement, the nature of the body, and the sensitiveness of 

 the instruments used. Thus when copper and zinc plates are 

 placed in a dilute solution of sulphuric acid there is an inter- 

 change of atoms between metal and acid, and the rate of inter- 

 change is so much greater in the case of zinc that the electrical 

 equilibrium of the system is at once destroyed, and this dis- 

 turbance is easily shown by means of suitable apparatus. Here, 

 as in all cases, the galvanic current is the manifestation of a 

 difference of atomic activity in two parts of a closed circuit, 

 and this in turn is due to a difference in "solution tension" or 

 " chemical affinity " of the substances employed. The diffusion 

 of liquids is attended by similar electrical phenomenon. For 

 example, when two solutions of different concentration of the 

 same substance are brought in contact, the greater solution 

 tension of the more concentrated solution forces its ions into 

 the weaker solution more rapidly than the ions of the latter 

 move in the opposite direction, and we have what is known as 

 a " concentration element." Since hydrogen and hydroxy 1 

 ions take the lead for rapidity of motion in solutions, we find 



that the more dilute solution of an acid is positively charged 



+ 

 (H) in the concentration element, while the more dilute solu- 

 tion of a base is always negatively charged (OH). 



We may say then, in general, that wherever there are dif- 

 fusion currents in non-homogeneous liquids, or — even more 

 broadly stated — where there are differences of solution tension 

 in the parts of a material body, there will be electrical differ- 

 ences of a corresponding magnitude. 



In view of these facts it is not at all surprising to find that 

 living organisms frequently show well-marked evidence of 

 electrical disturbances within their bodies. Considering the 

 great variety of substances which enter into the composition of 

 an ordinary plant body, the presence of diffusion currents as 

 an ever-essential condition, and the comparatively high resist- 

 ance offered by living tissues to the passage of electrical 

 currents, it is fair to expect a difference of electrical potential 

 in the parts of such a body when performing its normal 

 functions. 



