562 PLANT RESPONSE 



reacts to the action of salt, at least for a time, by an erectile 

 responsive movement. Under a less favourable tonic con- 

 dition, it responds by depression. That this latter is not 

 entirely due to plasmolytic action is seen from the fact that 

 the leaflet subsequently becomes erected, as is the case under 

 continuous stimulation. 



The localised and unilateral action of anode and kathode 

 on a pulvinated organ is as follows : 



The anode-make causes expansion, inducing convexity. 

 This effect attains its maximum in a short time. 



The anode-break induces contraction and concavity. 



The kathode-make induces contraction and concavity. 

 This effect is stronger and more persistent than the opposite 

 effect of expansion at anode-make. 



The kathode-break induces expansion and convexity. 



The polar effects on longitudinal growth are as follows : 



The anode-make causes expansion and acceleration of 

 growth. This effect attains its maximum in a short time. 



The anode-break causes contraction and transient retarda- 

 tion of growth. 



The kathode-make causes contraction and retardation of 

 growth. This effect is stronger and more persistent than 

 the opposite effect of acceleration at anode-make. 



The kathode-break induces an expansion and transient 

 acceleration of growth. 



The localised and unilateral action of anode and kathode 

 on a growing organ, results from the unilateral exhibition of 

 those growth-variations which have just been described. 

 Since a growing organ is virtually a diffuse pulvinoid, the 

 effects are exactly similar to those seem in a pulvinated 

 organ, already described. 



Owing to the fact that kathodic action is relatively 

 stronger than anodic, a feeble or moderate current flowing 

 through the soil exerts an excitatory action on roots, by 

 which the suctional activity of the plant is increased. The 

 result is an increased rate of growth, which is independent 

 of the direction of flow of the current through the soil. 



