Abscission of Flowers and Fruits of the Apple 



67 



RELATION BETWEEN WEIGHT OF THE FLOWER-BEARING SPUR AND ITS 



FRUITFULNESS 



Most writers on topics relating to fruit setting agree that the vigor of 

 the tree is a factor to be considered. It is generally assumed that excessive 

 vegetative growth is opposed to fruit production. No definite figures, 

 however, are available regarding the influence of the vigor of the indi- 

 vidual spur on fruit bearing. 



When the fruit bud opens in spring, a short spur is produced varying 

 in length from 0.3 to 2 centimeters. This new growth bears leaves later- 

 ally and a cluster of flowers terminally. It seems safe to assume that 

 this spur gro\vth is made at the expense of stored food. The stored food is 

 the result of photosynthetic activity 

 during the previous year. The 

 amount of this early spur growth 

 with its leaves and flowers can there- 

 fore be taken as an index to vigor. 



Weights of setting and of non-setting 

 spurs 



The relation of vigor to the fruit- 

 setting ability of the tree was studied 

 by ascertaining the weights of a large 

 number of flower-bearing spurs. The 

 spur growth of the current year was 

 cut from the parent spur just at the Fig. 2. 

 base of the ring of bud scales pro- 

 tecting the bud from which the cur- 

 rent year's growth came (fig. 2). 

 The spurs were weighed in a turgid 

 condition. The weights were taken early in the season, and any growth 

 arising from a lateral bud on the current season's spur was removed 

 before weighing. 



All flower-bearing spurs found on a given limb were considered; the 

 setting and the non-setting spurs were therefore produced on the same 

 parent branch. The data given in table 20 are representative of the 

 weights of setting and of non-setting spurs. 



According to the table, the setting spurs on a given branch are heavier 

 than the non-setting spurs on the same branch in all cases. It should be 

 noted that the average weight of spurs may be greater on one branch 

 than on others. More specific observations regarding this point are 

 discussed later (page 73). 



181 



PREPARATION OF SPUR PREVIOUS 

 TO WEIGHING 



The point C just below the ring of bud-scale 

 scars, B, indicates the point at which the present 

 year's growth, A, is cut from the preceding year's 

 growth, p E. The fruits are removed before the 

 spur is weighed. (Slightly reduced) 



