48 TRANSLOCATION IN PLANTS 



branch, on the other hand, had developed an average of 

 24 side shoots each, and these alone had borne over 1,200 

 leaves. The smaller shoots alone on the check branch 

 bore many times the number of leaves that was found on 

 the entire ringed branch while the three main shoots of the 

 check bore 24 times as many leaves as the corresponding 

 shoots on the ringed branch. Not only were there many 

 more leaves on the check branch, but the leaves averaged 

 about 65 per cent larger in area and 44 per cent heavier dry 

 weight per leaf, 140 per cent more total nitrogen per leaf, 

 46 per cent more nitrogen per square decimeter, 68 per cent 

 more nitrogen per gram of dry weight, 112 per cent more 

 total ash per leaf, 31 per cent more ash per square decimeter 

 of leaf area, and 50 per cent more ash per gram of dry 

 weight. Since the three main shoots of the check branch 

 bore about 24 times as many leaves as the corresponding 

 shoots of the ringed branch and since these check leaves 

 contained 2.4 and 2.12 times as much nitrogen and ash, 

 respectively, per leaf, the total nitrogen and ash moving 

 through the stem of the check branch must have been over 

 50 times those of the ringed stem. 



Although this evidence indicated rather clearly that the 

 xylem was not effectively carrying nitrogen and ash con- 

 stituents and that this lack of nutrient salts may have 

 accounted for the poor growth of the ringed stem, it was 

 recognized that the ring may have, for some other reason, 

 influenced growth and other processes of the parts above 

 it, and these in turn may have influenced solute transloca- 

 tion. It was also recognized that the ring had prevented 

 the formation of new xylem at the point ringed, and had 

 also reduced the formation of new stem tissues immediately 

 below the point of ringing. For these reasons other experi- 

 ments were carried out in which the ringing was done after 

 the leaf formation, shoot elongation, and xylem formation 

 were nearly or quite completed for the season. 



Representative data from such an experiment with 

 Ligustrum bushes are summarized in Table 9. For this 

 experiment matched stems were selected and one leaf from 



