CHAPTER III 



EVIDENCE FOR THE UPWARD TRANSPORT OF 

 NITROGEN AND SALTS THROUGH THE PHLOEM 



10. Effects of Ringing on the Upward Transfer of 

 Nitrogen and Ash Constituents. — Since considerable evi- 

 dence had accumulated which definitely indicated that 

 carbohydrates, though they are stored in the xylem, are 

 not readily transported longitudinally through these tissues, 

 it seemed desirable to determine the effects of ringing on 

 the upward transfer of salts absorbed from the soil solu- 

 tion, for these have been universally assumed to travel 

 with the transpiration stream. Many experiments were 

 therefore carried out to test the effect of ringing on the 

 upward transfer of solutes absorbed from the soil. The 

 details of several such experiments are presented in my 

 paper of 1923. 



It will be sufficient here to summarize briefly some of the 

 evidence presented in that paper. When branches of 

 peach trees were ringed early in the season just before bud 

 break, and sodium nitrate was then added to the soil, these 

 ringed branches made less growth than the check branches, 

 and the leaves also contained less nitrogen and ash. Such 

 results were obtained with all the trees experimented with, 

 but it will be sufficient to describe the results with one 

 tree. One arm of a small peach tree forked in the top was 

 ringed at a point where the stem was 2.5 cm. in diameter, 

 and the ring wound was protected with melted paraffin. 

 In spite of the fact that this ringed branch was the leader 

 and slightly larger than the other, the check branch by the 

 end of the season had made many times the growth of the 

 ringed one. The three largest shoots of the ringed branch 

 were found to have developed no side branches and bore 

 only 50 leaves in all. The three main shoots on the check 



47 



