TREE PHYSIOLOGY 



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into new tissues and are also used in strengthening other tis- 

 sues. Thus, in the apple, these materials are used in: (a) 

 making new terminal growth over the tree; (6) increasing the 

 diameter of the main limbs, trunks, and roots; (c) the pro- 

 duction of new root growth; (d) the formation of new fruit 

 spurs; (e) keeping the old spurs healthy; (/) the formation 

 of fruit buds for fruit production; and (g) developing the 

 individual fruits. 



Carbohydrates Are Essential for Fruit-Bud Formation. 

 The accumulation of carbohydrates in the tissues is generally 

 small during rapid growth, since the carbohydrates are largely 

 used in building and developing new tissues, if the supply of 

 moisture and nitrates is abundant. When rapid growth ceases, 

 carbohydrates accumulate and at this time, or shortly there- 

 after fruit buds begin to differentiate. 



Ringing and Notching. Additional evidences showing the 

 favorable effects of carbohydrate accumulation on fruit-bud 

 formation is found in ringing and notching. When vigorous 

 young trees are ringed (a narrow ring of bark removed from 

 the trunk without injury to the cambium layer) in May or 

 early in June, such trees usually form a large number of 

 fruit buds for the next year's crop, owing to the accumulation 

 of carbohydrates above the ring. In ringing, a section of the 

 tissue (phloem) through which the carbohydrates are trans- 

 located to the lower parts of the tree and roots is removed, 

 and as a result the concentration of carbohydrates is greater 

 in the tops of the trees. ^ 



Where whole trees are ringed by removing a strip of bark 

 around the trunk, a dwarfing of the trees often results. The 

 roots are cut off from their full supply of carbohydrates and 

 accordingly are checked in growth. This, together with the 

 dwarfing caused by the crop of fruit, makes the practice ques- 

 tionable when several years are considered. 



It is probable that more satisfactory results would occur 

 over a period of years if ringing were confined to one main 

 limb on the tree each year. By this means some fruit would 



