Chapter IX — 159 — Uptake and Movement 



gated the upward movement of dye approximately equaled the downward 

 movement, and the ratio was independent of the saturation deficit in the 

 plant if the measurements were made very quickly after the injection. This 

 led to the conclusion that the first equal injections were the result of released 

 tension. Long time measurements of dye penetration show the amount of 

 movement as a function of the amount of water deficit in the plant parts 

 toward which the dye is flowing. 



Kennedy and Crafts (1927) and Crafts and Kennedy (1930) 

 studied the rate of movement of eosin solution into the stems of wild morn- 

 ing-glory plants growing under varying conditions of temperature, humidity, 

 and soil moisture and which were cut under the solution. They concluded 

 that if the rate of transpiration exceeded absorption (causing tension in the 

 xylem) dye penetration was influenced chiefly by the amount of transpira- 

 tion before cutting, i.e., the saturation deficit. When transpiration was low 

 it varied directly with the amount of transpiration and inversely with soil 

 moisture. Brett (1943) has confirmed these results. 



Plant injection has become a standard practice in the treatment of min- 

 eral deficiency diseases including chlorosis, zinc deficiency, etc. A variety 

 of methods have been developed depending upon the nature of the chem- 

 icals to be supplied and the reaction of the tissues to them. Some applica- 

 tions are made as liquid through cut branches and bore holes at the base of 

 the tree ; others involve use of pure chemicals in bore holes or slits in the 

 bark, and some chemicals are readily absorbed through the leaves so the 

 injection is not required. 



Because Roach (1938, 1939) reviews much early work on this topic and 

 describes detailed methods used by him and his collaborators for diagnosing 

 and curing mineral deficiencies, only a few of the recent publications will be 

 mentioned. Bennett (1931), using solutions and dry salts, developed 

 methods for treating lime-induced chlorosis of pears and the adoption of 

 his dry-salt method has resulted in salvaging a large acreage of fruit trees 

 that were destined for removal. Over 75,000 trees had been treated by 

 1931 and the method has been widely used since. 



Roach (1938) and Roach and Roberts (1945) stress the use of in- 

 jection for diagnosing mineral deficiencies. In the latter paper the test 

 solutions used in detecting deficiency of N, P, K, Ca, Mg, Fe, Mn, Zn, Cu, 

 Ni, and B are described and all necessary equipment is pictured. Injection 

 methods for curative purposes for both liquids and dry salts are mentioned 

 and apparatus is illustrated. These methods are finding wide use in treat- 

 ing fruit trees. Their success depends largely upon a thorough knowledge 

 of the physiology of sap movement as the transpiration stream is largely re- 

 sponsible for distributing the chemicals. 



Much effort has been expended in attempts to inject insecticidal, fungi- 

 cidal, and bacteriocidal agents to better the welfare of plants. However, at 

 present, less success has attended this work than that on mineral deficien- 

 cies. 



Freezing of Stems: — Peirce (1936a, 1936 b) froze portions of intact 

 buckeye and castor bean stems with liquid air under various environmental 

 conditions, and, after detaching, tested the conductivity of the frozen portion 

 to gas by blowing through it. Under conditions of water deficit there seemed 

 to be evidence that some of the elements were not filled with ice. Such a 

 procedure might be faulty, however, because contractions and expansions 



