388 



Kessler, Moscicki, and Bak 



following growth inhibitors were tested: triiodobenzoic acid (TIBA), 

 maleic hydrazide (MH), coumarin (CM), dichloroanisole (DCA), and 

 m-tolylphthalamic acid (MTPA) (18). Decapitation of the terminal 

 end of the stem was introduced as an additional treatment and was 

 carried out just before the start of the experiments. 



Each tree was sprayed with solutions containing 100 p.p.m. of one 

 or another of the above substances. One terminal leaf of each plant 

 was then painted with 0.1 ml. of Ca^^ (0.8 ^c/ml). The same amount 

 of radiocalcium was applied to control plants which had been sprayed 

 with water as pretrcatment. For analysis the fifth leaf below the treated 

 one was collected, dried, and weighed. This leaf was washed and the 

 radioactivity counted. Both a thin end-window Geiger-Mueller tube 

 and a gas flow counter fitted with a micromil window (Nuclear-Chi- 

 cago) in an atmosphere of Q-gas were used. All counts are corrected 

 for background and self absorption to infinite thinness. The results 

 are expressed as total counts per minute (c.p.m.) per g. dry matter. 



For measurements of the time effect, six similar branches on each 

 tree were treated as above, and at intervals after the application of 

 Ca^s, samples were collected from these six branches. Thus, any 

 change in the movement of Ca could be detected. 



In another series of experiments the effect of different concentra- 

 tions of TIBA was tested. Concentrations of from to 100 p.p.m. of 



DAYS AFTER TREATMENT 



Fig. 1. The movement of foliar applied Ca" in l-year-old apricot trees and the 

 effect of MH and dichloroanisole upon this transport. 



