560 PLANT RESPONSE 



effects of anode and kathode (figs. 230, 231). It is to be borne 

 in mind that the growth of a plant, other factors remaining the 

 same, is dependent on its suctional activity. And this again 

 depends on the excitation of the root. Now, we saw that 

 though the effects of anode and kathode at make are opposite, 

 yet they are at the same time not equal. The anodic effect 

 is relatively small and short-lived, and the kathodic effect is 

 stronger and more persistent. Hence, though the effects on 

 the two halves of the root may be electrically opposed, yet 

 there will be a resultant differential effect of excitation, due 

 to the predominance of kathodic action. Hence an electrical 

 current, whatever be its direction, would excite the roots, 

 causing a greater suctional activity, with consequent enhance- 

 ment of growth. This 

 deduction I have been able 

 to verify by experimenting 

 on the variation of the rate 

 of growth of seedlings of 

 ^ ^ TT^f . • * , .■ c T, . Ory.za sativa when the soil 



Fig. 233. Effect in Acceleration of Rate . -^ 



of Growth of Seedling of Oryza sativa in which they groW was 



of Current through the Soil subjected to a current, 



The continuous line shows effect during a^„.;„^ . :., j 



passage of current through the soil Aowmg noW m one, and 



(I) from left to right ( ->), and (2) rom again in the opposite 



right to left (<-). Dotted line shows i- ^- ^, , 



effect on cessation of current. Record direction. 1 he growth- 



of growth taken under balanced con- record of a single seed- 

 dilions. ° 



ling was first taken under 

 balanced conditions (fig. 233). The electrical current was 

 next sent through the soil from left to right, and during 

 the continuation of this current, we see from the up curve 

 the acceleration of growth above the normal that took 

 place. The current was now stopped, and the former 

 induced acceleration was replaced by a brief retardation, 

 as seen in the down curve, after which the normal rate 

 was restored. The current was next reversed, and yet 

 the response was one of accelerated growth, and on the 

 stoppage of the current after a brief retardation there waix- 

 again a restoration of the normal rate. This experime-^'- 



