DORMANCY IN BUDS 231 



buds lose their dormancy quicker in the moist than in the dry condition, 

 but gave quite the opposite interpretation. He found by anatomical 

 studies that moisture favored the rapid development of periderm which, 

 in turn, cut down the oxygen supply to the buds and favored growth ; and 

 that freshly harvested tubers germinated rather promptly under 5 to 

 10 per cent oxygen pressure rather than at normal pressure. Peeling the 

 tubers about the eyes shortened the rest period because it led to the rapid 

 development of effective periderm. Two to 10 per cent of oxygen elimi- 

 nated apical dominance, so that several buds grew from each eye instead 

 of one bud from one of the apical or, seed end, eyes. Increasing the oxygen 

 above 20 per cent prolonged the dormant period. This is one of few cases 

 on record where reducing oxygen pressure below the normal favors growth 

 of flowering plants. Certain seeds are favored in germination by reduced 

 oxygen pressure. Perhaps storage at 35° C (95° F) ^^ hastens after-ripening 

 of potato tubers by increasing the development of corky periderm. 



About the time the Institute opened we had an inquiry from Bermuda 

 for some means of thro^^^ng freshly dug potatoes into immediate gro^\'th. 

 Bermuda had been using seed grown in Long Island, which had been har- 

 vested early enough in the summer to after-ripen before plantmg time in 

 Bermuda in early October. This seed was unsatisfactory; it became in- 

 fected ^\^th virus diseases during the season due to the abundance of 

 insect vectors on Long Island. It was estimated that the virus diseases 

 carried in the tubers reduced the yield about 50 per cent. Northern-growTi 

 seed could be obtained which was practically free from leaf roll and mosaic. 

 However, it was harvested in September and was not ready 'to grow for 

 some weeks after planting time in Bermuda. 



The Institute decided to organize a project to study dormancy in buds 

 much as it was studying dormancy in seeds. Dr. F. E. Denny, who had 

 recently developed the ethylene method of coloring citrus fruits, was asked 

 to head the project. Later a grant from the Herman Frasch Foundation for 

 Research in Agricultural Chemistry enabled the Institute to add two well- 

 trained biochemists, Drs. John D. Guthrie and L. P. IVIiller, as associates 

 on the project. These three scientists, with assistants, carried on the project 

 under the Frasch grant for eleven years, and it has been continued with a 

 slight change in the staff for nine additional years. As a result of these 

 studies some very effective chemicals have been found for throwing buds 

 out of dormancy and for inducing or maintaining dormancy. Much has 

 been learned about the metabolic changes brought about by the dormancy- 

 modifying chemicals in buds and the plants to which the buds are attached. 

 In this chapter we can cover only a few of the points of more general inter- 

 est. The details are published in more than seventy-five different articles. 



Chemicals That Force Dormant Buds 



Ethylene chlorhydrin and thiocyanates. In his original study of the 

 effect of 224 different chemicals for forcing dormant potato buds, Denny ^- ^ 



