CHANGES ACCOMPANYING BREAKING OF REST PERIOD / 



to their specific effect. It is, indeed, striking to find that the phe- 

 nomenon of growth is started by such different agencies as heat, 

 cold, increased and decreased water content, anesthetics, narcotics, 

 gases and liquids, bases and acids, salts singly or combined, elec- 

 tricity, mechanical injury, and in vacuo. In other words, while the 

 different agencies mentioned may not all have the same specific 

 effect on the plant, they all produce the same ultimate results, that 

 is, tend to shorten the normal rest period of plants. 



But how do all these various agencies affect the physiological 

 processes of the resting tissue? Do all have a similar influence, or 

 do some bring about growth in one way, for example, by desiccation, 

 and some in another, as for example, by increasing respiration? 

 These were some of the main questions to be answered by the inves- 

 tigations reported in this bulletin. 



Not very much experimental data have been contributed toward 

 explaining the specific influence exerted by the various agencies used 

 for breaking the rest period in plants. However, considerable has 

 been written regarding the probable action of rest period breaking 

 agents. Claude Bernard 1 thought that etherization caused a coag- 

 ulation of the protoplasm. Raphael Dubois 2 found marked dehy- 

 dration taking place in plant tissues which were etherized. Johann- 

 sen 3 pointed out that dehydration occurs only after the ether has 

 severely injured the tissue. Nevertheless, Dubois' experiments seem to 

 have influenced later authors to adopt the theory that ether and chlo- 

 roform have the same influence on plants as drying and freezing viz., 

 that they cause a desiccation of the living tissue. Aymard 4 supports 

 this view very vigorously. Stuart 5 seems to favor this hypothesis. 

 Regarding anesthetics he says: "Their effect upon the plant is to 

 arrest growth, extract moisture from the cell protoplasm, and thru 

 these physiological derangements, impart a severe shock to the whole 

 plant which when removed causes a decided growth reaction." 

 Similarly, he believed that toxic substances (acetone, alcohol, etc.) 

 and non-toxic agents (freezing, vacuum treatment, desiccation) "ar- 

 rest growth and remove moisture from the plant tissue much in the 

 same manner as anesthetics." It is quite apparent that warm water 

 baths which are very useful in shortening the rest do not bring about 

 a drying effect. In this case Stuart believes that "hot water imparts 



1. Bernard, Claude, See reference to Johannsen, p. 65. 



2. Dubois, Raphael, See reference to Johannsen, p. 65. 



3. Johannsen, W., Das Aetherverfahren beim Fruhtreiben, etc. Zweite 

 Ann. 1906. 



4. Aymard, J., See Howard Mo. Exp. Sta. Research Bui. No. 1, p. 24. 



5. Stuart, W., The Role of Anesthetics and Other Agents in Plant Forcing. 

 Vt. Sta. Bui. 150, pp. 451-480. 



