CATALASE AND OXIDASE CONTENT OF SEEDS IN RE- 

 LATION TO THEIR DORMANCY, AGE, VITALITY, AND 

 RESPIRATION 



By William Crocker, Plant Physiologist, Office of Physiological and Fermentation 

 Investigations^ and George T. Harrington, Scientific Assista^it, Seed-Testing Lab- 

 oratories, Bureau of Plant Industry, United States Department of Agriculture ^ 



INTRODUCTION 



For some years the Seed-Testing Laboratories of the Bureau of Plant 

 Industry has been using daily alternating temperatures for the germination 

 of certain seeds. In these alternations the lower temperature is used about 

 1 8 hours and the higher temperature about 6 hours of the day. Alter- 

 nating temperatures are found especially favorable for the germination 

 of the seeds of certain grasses: Johnson grass, Holcus halepensis L. 

 {Sorghum halepensis Pois.) ; bluegrass, Poa praiensis; and Bermuda grass, 

 Capriola dactylon (L.) Kuntze. For Johnson grass 30° C. for 18 hours 

 and 45° C. for 6 hours of the day have been found to be the most favor- 

 able alternation. Sudan grass, Holcus halepensis sudanensis (Piper) 

 Hitchc. (Andropogon halepensis sudanensis Piper), which is closely 

 related to Johnson grass and very similar to it in most respects, germi- 

 nates readily at constant temperatures. 



During the last three years (191 6-1 91 8) an extensive physiological 

 study of the behavior of the seeds of Johnson grass and Sudan grass has 

 been made in order to get some light on the reasons for the difference in 

 the requirements of the two regarding alternate temperatures for ger- 

 mination. Incidentally such a study has thrown much light upon 

 delayed germination and the physiology of germination in general. 

 Naturally seeds of several other grasses and of a number of other families 

 have been drawn into the investigation. The present paper reports one 

 phase of this extensive comparative study of the physiology of germination. 



MECHANICS OF DORMANCY 



A brief statement of the mechanics of dormancy in seeds can profit- 

 ably be made at this point, since it will throw light on experiments to be 

 reported later. There are two general means by which seeds are ren- 

 dered dormant even when they have morphologically mature embryos 

 and have all the external conditions necessary for germination. 



» The writers are under great obligation to the following organizations for supplies of seeds used in this 

 work ; To the Office of Forage Crop Investigations for Johnson grass and Sudan grass seeds of various ages, 

 together with daU as to time and place of collection; to the Seed-Testing Laboratories for several samples 

 of 23-year-old seeds of A maranthus retroflexus; and to the botanica 1 staff of the State College of Washington 

 for the collections of various species of Amaranthus made at Pullman, Wash. 



Journal of Agricultural Research. Vol. XV. No. 3 



Washington, D. C. (137) 0*^t. 21. 1918 



pp KeyNo. G-159 



