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Breaking The Rest Period Of Plants

( Originally Published 1920 )



THE object of greenhouse culture is to grow certain crops or blooms at a time and season when these cannot be produced outdoors. All plants undergo a period of rest. Bulbs, for instance, enter their resting state, when the leaves all die. No matter how cold, warm or wet, bulbs will not grow again before the fall. Howard* has found that it is very difficult to shorten this dormant period, at least during the earlier phases of the rest. He further found that of all treatments, drying, followed by injection with ether and Knop's solution (made up as follows: Calcium nitrate 1 gr., magnesium sulphate 25 gr., acid potassium phosphate 25 gr., and water 1 liter.), and combinations of these were most effective in shortening the rest period of bulbs. The injection may be accomplished by piercing the bulb with a hypodermic needle. Herbaceous perennials, too, like the bulbs, undergo a rest period. Frost, drying, and ether appear to be the most effective agents in breaking this rest period. To treat plants with ether, a galvanized iron chamber is preferred. The latter as used by Howard is shaped like a cylinder, with a diameter of about two feet and is made in two sections, each about three feet in length. The lower section is fitted with a bottom and at the top, around the rim, with a groove which is filled with fine sand. The rim of the upper section flares out) so as to accommodate a lid. The latter fits in tightly by being forced down in the sand. The second section of the cylinder is like the first, except that it is bottomless. When treating a large number of plants at one time, the second section is placed upon the first, the lower end being forced into the sand. The ether is poured in through an opening in the lid, which may be tightly closed by means of a screw cap. The amount of ether used is at the rate of 40 grams to each 100 meters of space. The lid is weighted with bricks to prevent its being pushed off by the ether vapor. Treatments should preferably be given in the afternoon, or where there is no likelihood of changes of temperatures. The results of the treatment are summarized by Howard in Table 14 on following page.

From Table 14, it is seen that with certain plants etherization breaks the rest period and hastens growth (fig. 13, a-f.) while with others the treatment has the opposite effect. In his investigations Howard* further found that the rest period of a large number of woody plants may be largely overcome by ether treatment (fig. 14, a-b.). On the whole, however, the use of anęsthetics is still in the experimental stage, although much that has been already discovered could be applied with great advantage commercially.



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