Etherization
Read about Etherization in the Standard Cyclopedia of Horticulture
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Etherization of plants. Etherization, as applied to plants, means strictly the forcing of a dormant plant into growth by subjecting the plant to ether vapors at certain concentrations in a closed chamber for a definite period of time, usually twenty-four to seventy-two hours. The plant after such treatment is placed under environmental conditions favorable for growth. Since in practice the use of chloroform is similar in its application and effects, it will be discussed here. The general nature of etherization was first noted by Johannsen in 1890, and following his investigation a wide stimulus was given to the commercial forcing of flowering shrubs. For other methods of forcing a dormant plant, see Rest-period. Before discussing the method of etherization, its effects and application, it is necessary first to have some idea of what is meant by the term rest-period or the condition of dormancy. Rest-period. Perennial plants, especially those in the temperate regions, in general have a season of growth and active metabolism followed by a period of quiescence as regards any outward manifestations of metabolism. During this period, not all of the vital processes are at a standstill and changes in the reserve food may be in progress, but the plant appears to be at rest "and is dormant. The rest-period begins with the advent of the unfavorable growth conditions of the autumn, and normally continues until the favorable conditions of the spring. One might reasonably assume that growing perennial plants removed from out-of-doors at the approach of autumn conditions to a greenhouse, would continue growth and not pass into the rest condition. One might assume, also, that if a plant in a dormant condition be brought into favorable conditions it would resume growth immediately. But experience and investigations show that many plants will not immediately continue growth, and, provided they do continue growth, it is at a slower rate. Dormant plants, that is those in the rest-period, may require considerable time before resuming growth. There are some plants that during dormancy respond quickly when brought into the greenhouse; there are others that remain dormant despite the most favorable environmental conditions. The rest-period in various species of Acer (maple), of Quercus (oak), of Fraxinus (ash), and of Fagus sylvatica, as well as other plants, is so well fixed as to make it almost impossible to force the dormant plants into growth by warmth and moisture alone. Special treatment is necessary, such as etherization. There are other plants in which the rest-period is not well established. These quickly respond to favorable growth conditions normally prevailing in a greenhouse. In many plants this rest-period has attained an almost habit- like character. The following table with data taken from results secured by Howard with branches brought into the greenhouse at Halle, Germany, is instructive: In the investigation made by Howard, 234 species were collected from October 20 to November 4, and of these only 125 grew; and of the 125, only 18 per cent began growth within a period of nine days. Between January 8 to 10, another collection was made including practically all the species of the first lot and others in addition, so that the number totaled 283 species. Of this number 244 grew, of which 50 per cent began growth within the first nine days. The species that did not grow when brought into the greenhouse January 8 to 10 made growth when brought into the greenhouse on February 26. From these and the results of other experiments the conclusion is drawn that plants in general tend to pass out of the rest condition as the season advances toward the spring. Dormancy is less stable in January than in November. This condition holds true not only for woody plants but also for bulbs and other herbaceous plants. Method of breaking the rest-period. The one method which has been largely employed for forcing dormant plants into growth is the etherization method. An air-tight chamber is provided, the size depending on the quantity or size of the material to be treated. The plants being placed in the chamber, it is tightly sealed except for a small opening through which ether may be introduced. Usually just below this opening is placed a sponge on which the ether is poured and then the opening is again sealed. If one desires to etherize a few bulbs, a wide-mouth bottle of two quarts capacity may be employed and the ether added in a small vial and the bottle then tightly stoppered. Special etherizing chambers are described for commercial work. The main desideratum is to have a chamber that will not permit of leakage of the ether vapor. The stopper must be securely fastened or weighted down. Quantity of ether.—The quantity of ether best employed in forcing plants may vary with the nature of the plant, the season of the year, and the temperature of the etherization chamber. In general, the quantity to be added varies from 5 to 15 cubic centimeters per cubic foot of space (10 cubic centimeters equal about one-third fluid ounce). Early in the rest-period at 60° F., one should use about 15 cubic centimeters per cubic foot of space. In the middle of the rest-period, one should employ less and the amount should be further decreased toward the end of the rest-period. If the relative humidity of the chamber is high, a slight increase in the quantity of ether may be made. If chloroform is used, the quantity should be one-fourth to one-third of the quantity of ether recommended. The following figures are from Stuart: Treatment Recommended For Plants At Different Seasons Time of exposure.—The time of exposure is also variable, being of greater duration in the early part and shorter in the latter part of the rest-period. In the early rest-period, a long exposure is given, varying from forty-eight to seventy-two hours to even as much as ninety-six hours. In case of long exposure, the practice is usually followed of making a forty-eight-hour exposure, after which the plant is removed from the etherization chamber for a day and then re-etherized for another twenty-four-hour period. Toward the middle and late rest-period, the time of exposure may be shortened as well as the quantity of ether. The results. The effect of etherization is to shorten the rest- period of the plant. Etherized plants come into bloom earlier and may be forced at lower temperature than unetherized plants. Howard found that seventy species of woody plants collected December 17 to 24 and etherized for forty-eight hours, opened their buds fully in an average of 20.3 days, while the untreated plants required an average of 28.1 days for the same development. Many experiments have been made with lilacs. Jannvek states that lilacs etherized August 24 were in bloom September 18. The following table compiled from results secured by Stuart show conclusively the value of etherization with lilacs: Influence of Ether And Chloroform On Lilacs In the foregoing table it is noted that treatment in the middle of December resulted in no beneficial effect. The plants at the time were in the middle rest-period, when growth-response requires no strong stimulation outside of normal growth conditions. In general it may be stated that lilacs if etherized before December 1 will respond markedly to the influence of etherization. General results show that etherized lilacs blossom in seventeen to twenty-five days. The saving in time may be eight to twenty days. Favorable results have been secured with flowering shrubs. Positive results have been reported frequently for Azalea mollis, for Viburnum and Astilbe. Negative or slight results have been reported for Deutzia gracilis, Prunus triloba, roses, and Spiraea prunifolia. Similar results have been reported for lily-of-the-valley. The method of action of the ether is not understood and any discussion of the subject is yet hypothetical. Etherization of bulbs. On the forcing of bulbs the evidence is unsatisfactory. At the Cornell Station, positive results were reported (see Bailey, "Cyclopedia of Agriculture," Vol. II: 29), but more recently Stuart has reinvestigated the forcing of bulbs and finds conflicting results. He states that the etherization of bulbs is not commercially practicable. Some unpublished data on the etherization of bulbs at the Cornell Station sustain this conclusion. Theoretically, those results are to be expected because the bulbs in practice are gathered in the late spring or early summer and then stored for months. After planting, the bulb is allowed to remain in a cold- frame for several months so that when brought into forcing conditions it is well over the rest-period and, indeed, has probably passed through its period by the time it is first planted. Effect on rhubarb.—Some positive results have been secured at the Vermont Agricultural Experiment Station with etherization of rhubarb. Different lots of rhubarb were etherized on December 9, January 9 and February 24. The first gave an increase over the control of 34.4 per cent, the second 89.7 per cent and the third 5.7 per cent. General conclusions.—Certain general rules may be applied to the practice of etherization: Bibliography.—Howard, W. L., "Winter Rest-Period in Plants. Missouri Experiment Station, Research Bulletin No. 1 (1910). Johannsen. W., "Das Aether verfahren beim Fruhtreiben mit besonderer Beruck- sichtigung der Fliedertreiberei." Jena, 1900. Zweite wesentlich erweiterte Auflage. Jena, 1906. Stuart, W., "The Ro1e of Anesthetics and Other Agents in Plant- Forcing," Vermont Experiment Station, Bulletin No. 150(1910). Lewis Knudson. CH
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
