754 Hall, Miller, a?id Herrero 



Translocation Experiments 



A series of experiments with cotton and Coleiis indicated that when 

 a single attached leaf was exposed to radio-ethylene it was absorbed 

 rapidly and transported to other parts of the plant. The concentra- 

 tion of ethylene in the treatment chamber varied from 600 to 660 

 p. p.m. and the plants were irradiated with light of 1,000 foot candles 

 intensity during the experiments. The treated and nontreated leaves 

 were harvested separately, dried, ground, and the tissue counted as 

 briquettes as described above. After 5 hrs. there was seven times more 

 activity in the nontreated leaves of cotton than in the treated leaves; 

 after 20 hrs. the nontreated leaves contained 30 times more activity 

 than the treated leaves. From 5 to 20 hrs. the treated leaves increased 

 in activity about eightfold. Essentially the same relative results were 

 obtained with Coleiis except the actual differences in activity be- 

 tween the treated leaves and the untreated leaves were not as great. 



It was noted in a number of experiments that the amount of 

 ethylene absorbed and transported is greatly influenced by whether 

 "fresh" or "aged" ethylene is used. This will be discussed in a sub- 

 sequent section. In the case of cotton it was found that after 5 hrs. the 

 treated leaf had absorbed and transported to the nontreated leaves 

 four times more "aged" ethylene than "fresh" ethylene. 



Comparison of plants maintained at less than 1 foot candle of 

 light to plants maintained at 1,000 foot candles during the treatment 

 period showed that the fixation of ethylene was greater in the dark, 

 but the translocation of the metabolites was governed by the same 

 factors, particuhuly photosynthesis and transpiration, which influence 

 normal translocation. Metabolite studies will be reported in a subse- 

 quent section. At the present time the transport form of ethylene is 

 unknown, but it appears that several metabolites may be involved. 



Cotton seedlings with two true leaves were fitted into 250 ml. 

 suction flasks with only the roots sealed tightly inside the flasks. Each 

 flask was filled with 200 ml. of distilled water and the roots immersed 

 to difl:ercnt depths. The shoots of the plants outside the flask were 

 illuminated with 1,000 foot candles of fluorescent light but the root 

 systems were kept in darkness. Ethylene-Ci^ (4.8 ml.) was injected into 

 the atmosphere above the roots to give 2,400 p. p.m. inside the flasks. 

 After 17 hrs. the plants were harvested and the leaves and roots pre- 

 pared for counting. The results (Figure 2A) show that ethylene may 

 be absorbed by roots and lower stems and transported to the leaves. 

 Up to 8 cpm/mg oi diy weight of leaves were found after 17 hrs. 

 in some experiments. Jt (an be seen that the depth of immersion of 

 the roots had little effect on the amount of metabolites present in 

 the leaves. 



