Killing of Plant Tissue by Low Temper.\ture 267 



the rapid temperature fall, while the greater resistance of the buds 

 following a prolonged cold period is due to the very slow temperature 

 fall with the resulting slow withdrawal of water from the cells, es- 

 pecially while the temperature is still near the freezing point. (See 

 Table 21.) 



The condition of the tree when it enters the winter should not 

 be lost sight of in considerations such as the above on the killing 

 from cold in winter. As mentioned previously, maturity plays an 

 important part in the resistance of winter tissue to low temperatures. 

 It may be said, however, that reference is had to the same trees for 

 1905 as for 1909. They were older in 1909 and were unquestionably 

 as mature. In fact in 1909 there was no apparent difiference be- 

 tween the hardiness of buds on the most vigorously growing trees 

 and those growing most slowly in this orchard, indicating that all the 

 trees went into the winter in good condition. That the condition 

 that favors greatest hardiness of buds is one of greatest maturity is 

 apparently common knowledge among peach growlers in northern 

 sections. On each such winter in the Missouri Experiment Station 

 orchard these trees that had ceased growing and become dormant 

 rather early the season before carried the largest number of buds 

 through the extreme cold uninjured. The same phenomena were 

 observed in Southwest Missouri following the winter of 1911-12 

 when there were no warm days to start the buds preceding the ex- 

 treme cold that killed them. In this case only those trees that were 

 large and matured early and had a large amount of small growth 

 down in the tree had any large percentage of buds to survive. These 

 same phenomena have been observed in orchards on other years in 

 Missouri. However, the average buds on a later maturing tree do 

 not seem to be appreciably less hardy than the average buds on ear- 

 lier maturing trees. In nearly all cases those buds that survived 

 were buds located on small spurs where there would be a whorl of 

 three or four leaves with only one or two buds on the spur, and there 

 are few such buds on a heavily pruned late maturing tree. It was 

 shown in Bulletin No. 74 of the Missouri Experiment Station that 

 generally the largest percentage of buds to survive cold are on the 

 base of the twigs of mature size; the next largest on these small spurs 

 mentioned above; and the smallest percentage to survive will be on 

 the ends of the twigs. However, with extreme cold that will kill all 

 of the buds at the base of the main twigs or practically all of them, 

 there will often be a few on the spurs; that is, the buds on these spurs 

 vary more as to hardiness than do the buds at the base of the whips. 

 This would naturally be expected since the conelition of growth with 



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