Lecture 4 — 93 — Movement and Distribution 



woody plants by the need for salt to pass from old 

 wood into new tissue. 



Our own data on girdled cotton plants and on 

 young citrus trees show that salt for a time may 

 pass upward past a girdle almost as well as in a 

 normal plant. The researches of Mason and his 

 colleagues (1937-1940) will be recalled at this point. 



Textfigure 28. — Illustrating varying conditions of 

 aeration in different anatomical regions. According to 

 one hypothesis this would have a role in movement of salt 

 to xylem system. (From Crafts and Bboyer, 1938). 



In some of our experiments with cucurbit plants a 

 section of the stem was killed by steam and still salt 

 could pass upward through the dead tissue for a short 

 time with little impairment in the amount of salt 

 moved. That organic nitrogen can move upward 

 fairly readily in living tissue seems possible, but 

 nitrate appears to move chiefly, if not entirely, in the 

 wood. 



The radioactive isotopes again furnish a convenient 

 tool for the further study of the path of movement of 



