Regressions of freezing tolerance for data from phase one of cold acclimation 

 were statistically significant (1 percent level) for all populations and accounted 

 for 64 to 96 percent of the variance. Response curves for three populations illustrate 

 the variety of observed responses to freezing severity (fig. 3) . Each of the curves 

 presented in figure 3 differs significantly (5 percent level) from each other for 

 either r or 2? in the regression equation. 



20 40 60 80 100 



SEVERITY OF FREEZING TREATMENT (PERCENT) 



Figure 3. --Response curves of freezing damage according to severity of the freezing 

 treatment for three populations during the first phase of cold acclimation. 



6 



