246 GROWTH OF PLANTS 



of low-temperature exposure grow with low vigor or are dwarfish. This 

 may happen if the forcing chemical is used in too low a dosage, but if the 

 chemical is used in sufficient dosage the vigor of growth is the same as that 

 induced by adequate low-temperature exposure. 



Various physiological and chemical changes ^^ were induced in dormant 

 lilac buds by optimum forcing dosages of ethylene chlorhydrin. There was 

 a marked increase in catalase, and an increase in water content and soluble 

 nitrogen compounds, but no significant change in amylase. There was 

 marked increase in respiration ranging from 20 to 100 per cent from early 

 to later stages. These changes were greater in the buds than in the twigs. 



It is possible that even more effective bud-forcing methods may be found 

 by mixing other effective chemicals with ethylene chlorhydrin. This is 

 especially hopeful if the mixtures show more than additive or synergistic 

 effect. Denny is investigating this possibility. In the case of trees and 

 shrubs it is desirable to find effective chemicals that can be added to the 

 soil and reach the buds through the roots and stems. It is possible that if 

 such chemicals can be found, buds of evergreens can be forced without 

 foliar injury. This is a good deal to hope for, since the leaves have rapid 

 transpiration and may accumulate more of the chemical than the dormant 

 buds. 



Metabolic Changes Induced by Chemicals That Force Dormant 



Potato Buds 

 Extensive studies were made of the effects of bud-forcing chemicals upon 

 the metabolism of potato tubers. These studies were directed at answering 

 two questions. In the soak treatment the seed pieces absorbed large quan- 

 tities of ethylene chlorhydrin, and upon exposure of the seed pieces to the 

 air the chemical disappeared from them faster than could be accounted for 

 by evaporation alone. Explaining the disappearance of ethylene chlorhy- 

 drin led to the discovery that not only this but several other foreign and 

 more or less toxic chemicals, when absorbed by plants, are tied up with 

 glucose to form glucosides or with other sugars to form other glycosides 

 which are, on the whole, less toxic to plants than the chemicals themselves. 

 The second object of the metabolic studies was to see whether some meta- 

 bolic change or changes brought about by the several forcing chemicals would 

 explain why the chemicals changed the buds from the dormant to the active 

 conditions. While no definite positive answer was gained for this question, 

 since various forcing chemicals showed opposite effects on such basic proc- 

 esses as respiration, the studies as a whole added much to our knowledge 

 of plant metabolism and the modification of metabolism by chemicals. 



Plants Transform Certain Toxic Foreign Chemicals into Less Toxic Glyco- 

 sides 



Miller ^^ early showed that the disappearance of ethylene chlorhydrin in 

 treated potato tubers was due in part to the chemical being transformed 



