390 



Kessler, Moscicki, and Bak 



300 



kiJ 



< 

 >- 



tr. 

 o 



200 - 



DC 

 Hi 

 0. 



in 



Z 



o 

 o 



100- 



DAYS AFTER TREATMENT 



Fig. 3. The effect of decapitation, coumarin, and MTPA upon the basipetal 

 transport of Ca*' in 1 -year-old apricot trees. 



241 c.p.m. for the control (Figure 1). This drop in radioactivity must 

 be interpreted as being caused by a stop in the supply of Ca^^ from 

 the treated terminal leaf, while Ca^^ continued to move out from the 

 counted leaves. 



If we compare the effect of these treatments upon the movement 

 of Ca^^ in one-year-old trees to that in 6-year-old trees, similar trends 

 are obtained. From Table 1 it can be seen that in 6-year-old apricot 

 trees, there was a considerably greater movement of foliar applied 

 calcium than in younger trees. In the old control trees the radioactiv- 

 ity reached 15,560 c.p.m. on the 7th day after the treatment, as against 

 241 c.p.m. in the young controls (Figure 1). TIBA again showed a 

 considerable promoting effect, while the radioactivity in MTPA- 

 treated leaves dropped as before, after an initial stimulative effect. It 

 is of particular interest that in this case decapitation strongly inhib- 

 ited the downward movement of Ca^^^ As previously stated, we must 

 also assume that in older trees MTPA stops the movement of Ca-*-"^ 

 from the terminal treated leaf after a time while Ca^^ continues to 

 move out from the counted leaf. Preliminary experiments in which 

 the radioactivity of various leaves along the shoots was counted 

 showed this assumption to be apparently true (Table 2). 



