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

Abstract

1971. Electrical stimulation and its effects on growth and ion accun~ulation in tomato plants. Can. J. Bot. 49: 1809-1815. 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 pA per plant with the plant negative to the ground. A reduction in growth occurred when the plants were treated with 15 pA positive to the ground or with any currents of magnitude greater than 30 pA per plant. The increased ion accumulatioil 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. IntroductionElectrical stimulation of plants is an attractive hypothesis but relatively unexplored scientifically. Both Lund (1931) and Waller (1925) showed that plants exhibit a constantly fluctuating potential difference or gradient, between the aerial part, the root, and the soil. Breazeale et al. (1951) and Breazeale and McGeorge (1953) demonstrated that cation uptake could be stimulated by application of controlled direct voltage and suggested that cation uptake by plants is an electrical phenomenon. Fensom (1957) studied the bioelectric potentials of plants and postulated an electrokinetic theory of transport. He attempted to alter the water intake of freshly cut maple shoots by applied voltage, up to 45 V (1962). Small electroosmotic flows were induced towards the cathode and from time to time a sudden surge of water flowed into the shoots. This surge seems now to be attributed to a summation of action potential~, for not only was the flow of short duration, but it was also associated with artificial guttation.Several workers such as Blackman et al. (1923) andBriggs et al. (1926) have attempted to influence plant growth with applied electricity by suspending a charged network over the plant,

Induction by Electric Currents of Ethylene Biosynthesis in Cucumber (Cucumis sativus L.) Fruit

“…These results indicated that the applied current may act as a kind of stress. Electric currents have various effects on plant physiology, and seem to promote polar transport of auxins in seedlings (4,9,25) and cultured tissue (11), and ion uptake by tomato plants (2), which in turn affects growth and differentiation. In those reports, the electric currents used were on the order of microamperes.…”

Air anions improve growth and mineral content of kale in plant factories

“…In previous studies, the uptake rates of macroelements such as N, P, Ca, and Mg were affected by an externally applied electric field (Murr, 1965;Murr, 1966). Black et al (1971) reported an increased absorption A B…”

“…Similarly, cations are likely to be attracted toward the negative electric field formed by air anions. The increased cations, including K + , could expand guard cells in leaf epidermal tissues and subsequently open the stomata (Black et al, 1971;Robinson, 1985). However, further studies are required to understand the underlying mechanism.…”

Different root growth patterns of tomato seedlings grown hydroponically under an electric field

“…In the presence of an EF, chemio-osmotic modifications of ion transport (an equivalent of salt influx or salt efflux driven at the expense of an equivalent of electrogenic proton efflux) could occur in roots (Robinson 1985). Furthermore, the increased ion accumulation seems not to be merely a passive movement under the applied potential, and it is thought that small currents could stimulate or inhibit active ion pumps or alter the internal distribution of growth-regulating compounds (Black et al 1971, Robinson 1985). An interesting observation could be related to another hypothesis: the root orientation in the growing medium.…”