CIRCULAR No. 377 NOVEMBER 1935 



UNITED STATES DEPARTMENT OF AGRICULTURE 



WASHINGTON, D. C. 



VERNALIZATION EXPERIMENTS WITH FORAGE 



CROPS 



By Roland McKee, senior agronomist, Division of Forage Crops and Diseases, 



Bureau of Plant Industry 



CONTENTS 



Page 

 Introduction 1 



Materials and methods 2 



Page 



Experimental results 4 



Summary n 



INTRODUCTION 



Studies reported by a number of investigators have called attention 

 to the influence of environmental factors during the germination 

 phase of growth on the later development and fruiting of the plant. 

 This general phenomena has been designated "vernalization." It 

 also is referred to under the term "iarovization" or "yarovization. " 



The economic objective of vernalization is the shortening of the 

 vegetative period and increasing yields of both seed and forage. The 

 hypothesis of Lysenko, 1 who has been the chief proponent of the 

 application of this principle, may be stated as follows: The con- 

 ditioning for sexual reproduction and vegetative growth in a plant may 

 occur in the seed when the embryo has started development but has 

 not yet, or scarcely has, broken the seed coat, if proper environmental 

 conditions are provided the seed at this time. 



Thus vernalization is practically a seed treatment that influences 

 the plant in its later stages of development. The seed is started into 

 growth by the application of a limited amount of moisture and then 

 subjected to other controlled factors: Temperature, light, darkness, 

 and time. The growth of the seed is arrested or controlled by limit- 

 ing the amount of moisture, and in the case of seed treated at low 

 temperature the cold is a limiting growth factor. 



In the case of winter wheat and other so-called "winter annuals", 

 the vernalization process consists of adding water to the seed in an 

 amount that will scarcely or just bring the seed into visible germina- 

 tion. This will require a 1- to 2-day period with the temperature of 

 the processing chamber kept at 10° to 12° C. The seed is then 

 transferred to a temperature of 3° to 5° and the moisture maintained 

 by addition of water when necessary, and the seed frequently stirred. 

 The time required in the cool room will vary, depending upon the 

 temperature and variety of seed, but from 35 to 45 days is average. 

 It has been pointed out by Lysenko that vernalization should be 



i Lysenko, T. D., [iarovization in agriculture.] Odessa Ukrainskii Inst. Selectii Biull. Iarovizatsii 

 nos. 1-3, illus. 1932. [In Russian.] 



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