completely inactivated in 3 hours when sprayed on bean leaves (9). Surface inactivation 
of pimaricin was thought to be the result of either oxidation or breakdown due to ultra- 
violet exposure. This same antibiotic after it had been absorbed and translocated into 
a leaf, however, was not inactivated during this period. 
Some therapeutants absorbed by the leaf, however, are degraded or changed rather 
slowly. For instance, a relatively large amount of the actidione applied to cherry leaves 
was unchanged even after 3 weeks (18). Other research resulted in the recovery and 
identification of this compound from wheat seedlings 5 weeks after application (61). 
Similarly, streptomycin was detected unchanged in tobacco leaves 5 weeks after spray 
application (21). 
On the other hand, some therapeutants absorbed by the leaf are changed more 
rapidly. The antibiotic F-17 was altered to suchan extent in bean leaves after 5 days that 
all its therapeutic activity was lost (47). 
The rate of inactivation of the therapeutant also depends upon the plant species. For 
example, vancomycin was completely inactivated in tomato and tobacco plants within 
2 days while in the case of cucumber some of the antibiotic was unaltered for at least 
10 days. The amount of antibiotic used is also important since when applied in larger 
amounts vancomycin remained unchanged in all of these plants for a relatively long time. 
Most therapeutants are not readily translocated from leaves to roots. The antibiotic 
vancomycin, however, appears to be an exception. This compound is translocated un- 
changed from treated leaves to other parts of plants including roots. In fact the con- 
centration of vancomycin that accumulated in roots of cucumber amounted to 16 micro- 
grams per ml. of plant juice (37). 
Various hypotheses have been proposed concerning the way these therapeutants may 
break down in leaves and also other plant parts (17). 
Application to Stems 
The upward movement of unaltered streptomycin applied to stems was first studied 
by our group (51). The therapeutant, when translocated to leaves, had a half-life of about 
7 days on the basis of a bacterial assay. This upward translocation was associated with 
the transpiration stream and no downward movement (phloem transport) was detected. 
The rate that this antibiotic moves up stems is illustrated in work on hops. Strepto- 
mycin was absorbed and moved up the stem 3 inches within 30 minutes (32). 
Application to Roots 
Many antibiotics are absorbed by roots and readily translocated upward to above- 
ground parts (4, 5, 13, 25). Some therapeutants, however, accumulate in roots and are 
not readily moved upward (6, 7). For example, Crowdy, et al.(4) showed that sulpha- 
guanadine is almost completely retained by roots. 
The fate of therapeutants following root treatment also varies with the kind of plant 
used, This is clearly shown by the rapid upward movement of streptomycin from roots of 
tomato contrasted with the relatively slow upward movement following absorption of this 
compound by roots of broad bean. In this work more antibiotic accumulated in tops of 
tomato than accumulated in those of broad bean plants (4). In addition, distribution of 
therapeutants in the aboveground parts of plants varies with the kind of plant used. For 
example, Crowdy (4) and Dye (13) showed that streptomycin accumulated primarily in 
lower leaves of peach seedlings while this same therapeutant attained highest con- 
centrations in the upper leaves and stems of tomato. 
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