142 



FUNDAMENTALS OF FRUIT PRODUCTION 



Table 27.- 



-The Phosphorus Content of a 7-year Old Apple Tree^^ 

 (Expressed in percentages of dry weight) 



Phosphorus, like nitrogen, is present in greatest amounts in the younger 

 roots and branches and is at a maximum in nearly all tissues when the buds are 

 swelling (see Table 27). The chief difference between phosphorus and nitrogen 



035 



0.30 



o.es 



0.20 



0.15 



0.10 



Fig. 15. — Phosphorus content of apple spurs in percentages of dry weight; bearing 

 spurs represented by continuous lines, non-bearing spurs by broken lines and barren spurs 

 by dot-dash lines. {.After Hooker y^'^) 



is that phosphorus reaches a minimum in most tissues in May when the tree is 

 in bloom, while nitrogen does not reach a minimum until July when active growth 

 is over. In all woody tissues there is an accumulation of phosphorus, as of nitro- 

 gen, in the fall, indicating storage. 



In Spurs. — Figure 15 shows the seasonal variations in the phosphorus content 

 of apple spurs. 100 In non-bearing and in barren spurs, the variations are similar 

 to those in other woody tissues, with a minimum in May. However, in June 



