RESEARCH SUMMARY 



Freezing tests were conducted to follow cold acclimation 

 in seedlings representing 51 populations of Pseudotsuga menziesii 

 var. glauca. For each of six dates between August and December, 

 twigs from 2 -year-old seedlings growing in a common environment 

 were frozen to each of six test temperatures. Injury from 

 freezing was scored by leaf discoloration. 



Hardiness developed at a rate associated with the minimum 

 temperature. During the early stages of cold acclimation, 

 variation in the hardiness of populations was related to geo- 

 graphic and ecologic factors of the seed source. Multiple 

 regression analyses accounted for 38 percent of the variance 

 among populations and showed that populations of greatest 

 hardiness in early autumn were from relatively high latitudes 

 and high elevations. But, during late stages of cold acclima- 

 tion, variation in hardiness among populations could not be 

 related to factors of the seed source. 



CONTENTS 



Page 



INTRODUCTION 



1 



MATERIALS AND METHODS 



1 



RESULTS 



5 



DISCUSSION 



9 



PUBLICATIONS CITED 



11 



