Electrical stimulation and its effects on growth and ion accumulation in tomato plants

The effect of small increments of direct current on the growth and ion uptake in Scotia tomato plants was determined. The natural endogenous current in the plant was first assessed and the current applied to reinforce or oppose the natural with three treatment durations per day. Significant increases in linear growth (5 to 30%) were obtained and also significant increases in uptake by the plants of K, Ca, and P when currents were between 15 and 3 μA per plant with the plant negative to the ground. A reduction in growth occurred when the plants were treated with 15 μA positive to the ground or with any currents of magnitude greater than 30 μA per plant. The increased ion accumulation seems not to be merely a passive movement under the applied potential, and it is thought that small currents may stimulate active ion pumps or alter the internal distribution of growth-regulating compounds in a somewhat erratic manner.