PLANT NUTRIENTS AND THEIR ABSORPTION 



103 



In Tissues of Different Age. — Age is likewise an important factor 

 influencing ash content. The percentage of ash increases with age in 

 the leaves and wood, but diminishes in the roots, branches and fruit. 

 Though in these last it increases in absolute amount, the proportion falls 

 off since organic matter increases at a greater rate. Table 6 shows the 

 increase in ash content of beech wood with age. 



Table 6. — Ash Content of Beech Wood^os 

 (In percentages of dry weight) 



Years of Rings 

 1 to 15 

 15 to 25 

 25 to 35 

 35 to 45 

 45 to 60 

 60 to 83 

 83 to 94 (sap-wood) 



1.162 

 0.825 

 0.645 

 0.612 

 0.555 

 0.458 

 0.205 



At Different Seasons. — An increase in the percentage ash content 

 of apple, pear, cherry and plum leaves during the season is shown in 

 Table 7. The absolute amount of ash present declines, however, before 

 the leaves fall (Table 8). Developing fruits, on the other hand, show a 



Table 7. — Ash Content of Leaves^^^ (in percentages of dry weight) 



