REST IN BUDS OF WOODY PLANTS 203 



TABLE I 



EFFECT OF CLIMATE ON DATE OF FULL BLOOM OF SANTA ROSA PLUMS 



Location 



Date of full bloom 



warm winter cold winter 



Jerusalem (mountain crest) March 31 March 10 



Affulah (central valley) April 3 March 8 



Mishmar H. (northern coastal valley) April 5 March 2 



Rehovot (southern coast) April 10 March 9 



Thus, a cold winter, a longer period of chilling, reverses the 

 abnormal situation brought about by the warm winter, i.e. a 

 certain period of chilling is required in order to terminate rest. 

 I should like now to show you the experimental effect of 

 chilling. Pelee^, working in our laboratory, placed resting Kelsey 

 plum shoots for various periods into a refrigerator at 4°. As 

 Table II shows, increased periods of chilling progressively 



TABLE II 



EFFECT OF DIFFERENT PERIODS OF CHILLING DURING REST ON THE AWAKENING 



OF KELSEY PLUM BUDS 



Chilling period Blossoming Open buds 



(days) date (% of total buds) 



advanced the awakening of buds in spring. One week of chilling 

 put forward bud opening by about a week, while chilling for 

 56 days advanced wakening by as much as 33 days. Futhermore, 

 chilling not only advanced the date of bud opening, but also 

 increased the number of buds which opened. Seven per cent of 

 buds opened on the control shoots; one week of chilling doubled 



References p. 208 



