The influence of electricity upon vegetation has been the subject of numerous investigations. Some have been made to ascertain the effects of the electric current through the soil; others to ascertain the effect of the electric light upon growth through the air. Among the latter are those of Prof. L.H. Bailey of the Cornell University Agricultural Experiment Station. In Bulletin No. 30 of the Horticultural Department is given an account of experiments with the electric light upon the growth of certain vegetables, like endive, spinach, and radish; and upon certain flowers like the heliotrope, petunia, verbena primula, etc. The results are interesting and somewhat variable. The forcing house where the experiments were carried on was 20 × 60 ft., and was divided into two portions by a partition. In one of these the plants received light from the sun by day and were in darkness at night. In the other they received the sunlight and in addition had the benefit of an arc light the whole or a part of the night. The experiment lasted from January until April during two years, six weeks of the time the first year with a naked light and the balance of the time with the light protected by an ordinary white globe. It is not the purpose here to enter into any great details, but to give the general conclusions.
The effect of the naked light running all night was to hasten maturity, the nearer the plants being to the light the greater being the acceleration. The lettuce, spinach, etc., "ran to seed" in the "light" house long before similar plants in the dark. An examination of the spinach leaves with the microscope showed the same amount of starch in each, but in the electric light plants the grains were larger, had more distinct markings and gave a deeper color with iodine.
With lettuce it was found that the nearer the plants were to the light the worse the effect; and conversely those furthest away were the best developed. Cress and endive gave the same results. In the case of the latter, some of the plants were shaded from the light by an iron post, and these grew better and were larger than those exposed to its direct rays. The average weight of eight plants in full light was 49.6 grains, as opposed to an average of six plants in the shade of 93.8 grains. Radishes were strongly attracted to the light and moved toward it during the night. During the day they straightened up, but moved again toward the light at night. The plants nearest the lamp made a poor growth and were nearly dead at the end of six weeks. Averaging the weight of plant, of top and of tuber, it was found that those grown in the dark were heavier in every instance than those grown in the light; and the percentage of marketable tubers from the light-grown plants was twenty-seven, as opposed to seventy-eight in the dark. Chemical analyses showed the plants in the light to be more mature than those in the dark, although they were much smaller. Dwarf peas showed the same facts, those in full light being smaller than those in the dark. The former bloomed a week earlier than the latter, but the production of seed was less, being only about four-sevenths as great.
Further experiments were made by excluding the sun during the day and exposing the plants to the diffused electric light only. In all cases, with radishes, lettuce, peas, corn, and potatoes, the plants died in about four weeks. Only a little starch and no chlorophyl was found in the plants deprived of sunlight and only receiving the electric light. Thus the experiments with a naked light showed conclusively that "within range of an ordinary forcing house the naked arc light running continuously through the night is injurious to some plants." In no case did it prove profitable.
Experiments with the light inclosed in a white globe and running all night were different in their results. The effect was much less marked. Lettuce was decidedly better in the light house; radishes were thrifty but did not produce as much as in the dark house. A third series of experiments with the naked light running a part of the night only were also made. Radishes, peas, lettuce, and many flowers were experimented upon. The lettuce was greatly benefited by the light. "Three weeks after transplanting (Feb. 5)," we are told, "both varieties in the lighthouse were fully 50 per cent. in advance of those in the dark house in size, and the color and other characters of the plants were fully as good. The plants had received at this time 70½ hours of electric light. Just a month later the first heads were sold from the light house, but it was six weeks later when the first heads were sold from the dark house. In other words, the electric light plants were two weeks ahead of the others. This gain had been purchased by 161¾ hours of electric light, worth at current prices of street lighting about $7."
This experiment was repeated with the same results. In the second experiment the plants receiving eighty-four hours of electric light, costing $3.50, were ready for market ten days before the plants in the dark house. The influence of the light upon color of flowers was variable. With tulips the colors of the lighted plants were deeper and richer than the others, but they faded after four or five days. Verbenas were injured in every case, being of shorter growth and losing their flowers sooner than those in the dark house. "Scarlet, dark red, blue and pink flowers within three feet of the light soon turned to a grayish white." Chinese primulas seven feet from the light were unaffected, but those four feet away were changed. Lilac colors were bleached to pure white when the light struck them fairly. An elaborate series of tables of the effect of the light is given in the paper. The author believes it possible that the electric light may be used some day to pecuniary advantage in floricultural establishments.
These experiments naturally open up many questions. Those which will be of most importance to the practical man will be such as relate to the benefits to be derived from the use of the electric light. That electricity has a great effect upon vegetation can no longer be denied. What remains now is to ascertain how to use the force with the most economy and to the best advantage. If by its use early vegetables will be made earlier, bright flowers be made brighter, it will be a question of only a short time before it will come into general use. To the student of plant physiology there are also many questions of interest, but into these it is not the intention to enter. Prof. Bailey's general conclusions are, in part, as follows: "There are a few points which are clear: the electric light promotes assimilation, it often hastens growth and maturity, it is capable of producing natural flavors and colors in fruits, it often intensifies colors of flowers and sometimes increases the production of flowers. The experiments show that periods of darkness are not necessary to the growth and development of plants. There is every reason, therefore, to suppose that the electric light can be profitably used in the growing of plants. It is only necessary to overcome the difficulties, the chief of which are the injurious influences upon plants near the light, the too rapid hastening to maturity in some species, and in short the whole series of practical adjustments of conditions to individual circumstances. Thus far, to be sure, we have learned more of the injurious effects than of the beneficial ones, but this only means that we are acquiring definite facts concerning the whole influence of electric light upon vegetation; and in some cases, notably in our lettuce tests, the light has already been found to be a useful adjunct to forcing establishments.... It is highly probable that there are certain times in the life of the plant when the electric light will prove to be particularly helpful. Many experiments show that injury follows its use at that critical time when the planetlet is losing its support from the seed and is beginning to shift for itself, and other experiments show that good results follow from its later use.... On the whole, I am inclined toward Siemens' view that there is a future for electro-horticulture."
JOSEPH P. JAMES.
Washington, Jan. 20, 1892.