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EFFECT OF ELECTRICITY ON PLANTS 



EFFECT OF ELECTRICITY ON PLANTS 



By G. E. Stone 



The relation that exists between electrical 

 stimulation and plant growth has been a subject of 

 much study, covering a great range of methods and 

 conditions, and producing varied and conflicting 

 results ; but the question has not yet had the care- 

 ful and systematic study necessary to the formu- 

 lation of rules for practical application. Much 

 has been written on the subject, and the reader 

 will find a few citations at the end of this article. 

 It is here possible to give only a very general 

 outline of the experimental methods that have 

 been tried and the results. 



Historical sketch of methods and results. 



Investigations pertaining to the effects of elec- 

 tricity on plants have been made by various ex- 

 perimenters for 150 years or more. It might be 

 supposed that electricity, which so universally 

 manifests itself in nature, would under certain con- 

 ditions be capable of acting as a stimulus to plants. 

 That the roots of plants are susceptible to the 

 influence of galvanic currents (galvanotropism) 

 has been shown by the experiments of Elfving, 

 Brunchorst and others ; and Hegler has shown that 

 the aerial hyphse of Phyeomyces nitens are nega- 

 tively electrotropic ; that is, they bend away from 

 Hertz waves. It has also been known for some 

 time, through the experiments of Kunkel and 

 others, that electric currents exist in the plant 

 itself. The cause of these currents has been attrib- 

 uted to minute streams of water passing through 

 the plant. The experiments of Haake have shown 

 that differences in the electrical potential in the 

 plant are chiefly caused by metabolism and res- 

 piration. 



The influence of current electricity on plants has 

 received the most attention. Attention was first 

 called to the influence of electricity on growing 

 plants about the middle of the eighteenth century. 

 The experiments made by Dr. Mainbray, of Edin- 

 burgh, in 1746, were among the first. He electrified 

 two myrtles for a period of one month, and reported 

 that not only was their growth accelerated but 

 that they put forth blossoms, which was not true 

 of myrtles not electrified. About the same time, 

 Nollet, a distinguished French physicist, who had 

 heard of Mainbray's experiments, took up the sub- 

 ject. He had previously been occupied with the 

 phenomena connected with the behavior of fluids in 

 capillary tubes, and Mainbray's experiments sug- 

 gested to him the possibility of the increased 

 growth in plants being due to the increase in the 

 flow of sap brought about by electrical stimulation. 

 His first experiments were made on various fruits, 

 which after being weighed were electrified and then 

 weighed again, and the result showed that elec- 

 tricity considerably accelerated evaporation. In 

 1747, Nollet experimented with two wooden pots 

 filled with earth, in which were planted mustard 

 seeds. One was treated daily with an electrical 

 machine, the other being kept as a check. He found 

 as a result of electrifying that germination was 



considerably increased, and in the course of a week 

 or more the electrified plants were nine inches 

 high, while the non-electrified ones were only three 

 inches high. Nollet repeated the experiment a 

 number of times with various plants, always 

 obtaining the same result. He found, howeyer, 

 that the electrified plants were, as a rule, weaker 

 than the non-electrified. Jallabert, in 1746, re- 

 peated Nollet's experiments on mustard and cress 

 seeds, and obtained similar results. He also elec- 

 trified bulbs of hyacinths, jonquils and narcissus 

 placed on cakes of resin in glasses filled with 

 water, the resin being connected with wires leading 

 to a frictional machine. He found, as had Nollet, 

 that the electrified ones gave off more moisture 

 than the non-electrified ones, and also that the 

 electrified plants grew more rapidly. Their leaves 

 were larger and their flowers opened sooner than 

 the ones not electrified. 



Experiments were made about the same time 

 also on bulbs planted in boxes, with similar results. 

 In 1747, Boze electrified several different kinds of 

 shrubs, the growth of which was accelerated. 

 Similar results were obtained by Menon, in 1748. 

 In 1771, Sigaud de la Fond experimented with 

 bulbs, and found that when they were electrified 

 they grew faster and formed more healthy plants. 



De Lacepede, in 1779, found growth and germina- 

 tion invariably accelerated by the use of electricity. 

 Marat, in 1782, experimented with lettuce and ob- 

 tained positive results. Bertholon subsequently 

 repeated the experiments of Nollet and obtained 

 similar results, and he moreover made many obser- 

 vations in regard to the effects of electricity on the 

 ripening of fruit, color of fiowers, and the like. He 

 was the first to attempt to apply electricity in a 

 practical way in the growth of crops, and he even 

 went so far as to recommend it as a panacea for all 

 diseases caused by insects and fungi. Achard, De 

 Saussure and Gardini likewise reported beneficial 

 results from the use of electricity. 



Gardini stretched iron wires over his garden at 

 Turin for the purpose of experimenting with atmos- 

 pheric electricity. After a short time the garden, 

 which had been unusually prolific, began to fail, 

 the plants became unfruitful and wilted. Ingen- 

 housz and Schwankhard, in 1785, made experiments 

 with plants cultivated in Leyden jars filled with 

 water, and obtained negative results. The experi- 

 ments were criticized by Duvarnier, who maintained 

 that the methods employed were not satisfactory. 

 Ingenhousz's negative results were confirmed by 

 Sylvestre, Paets, Van Troostwyck and Krayenhoff. 

 Ingenhousz and von Breda repeated Gardini's 

 experiments with overhead wires across a garden, 

 but both failed in observing any effect whatsoever 

 on the plants. In 1768, Carmoy sowed grains of 

 wheat in electrified tin vessels and found germi- 

 nation and growth accelerated. Rouland secured 

 negative results with cress seeds planted on plates 

 of cork in electrified porcelain vessels filled with 

 water. D'Ormoy electrified mustard and lettuce seed 

 for several days in moist earth and found their 

 germination always accelerated. Bertholon enclosed 

 seeds of turnip, endive and spinach in tin-foil and 



