It is well known that many regulating compounds are readily degraded when in 
contact with moist soil (2, 56). Soil microorganisms probably account for most of this 
degradation. Moisture plays an important role in governing the rate at which regulators 
are broken down in soils. For example, 2,4-D remained biologically active for only about 
2 weeks when stored in moist soil at the rate of 20 mg. per pound of soil whereas in 
dry soil it remained active for 1} years (45). 
Some regulating compounds, on the other hand, remain active when mixed with moist 
soil for long periods. For example, the quaternary ammonium compound Amo-1618 
remained active in moist soil for a period of over 10 years when incorporated at a rate 
of 50 and 100 pounds per acre. Even 1 pound per acre remained effective for about 
5 years (34). 
Once absorbed by the root, regulating compounds are translocated throughout the 
plant mainly upward through tracheary elements (30, 31). Little research has been di- 
rected toward gaining an understanding of the metabolism of regulating compounds by 
roots since their application has for the most part involved aboveground parts. 
Applied to Other Plant Parts 
Regulating compounds are absorbed in biologically effective amounts by some kinds 
of fruits, since these substances hasten growth or maturity of those such as pears, 
apricots, apples, and bananas. Maxie and his coworkers (36) found that C!4-_labeled 
2,4,5-trichlorophenoxyacetic acid applied to intact branches of apricot trees was present 
in the mesocarp of the fruit in. detectable amounts within 3 days after the trees had 
been sprayed. Within 10 days C was detected in the embryos and integuments and 
the amount increased until the fruit was mature. At least some 2,4,5-trichlorophenoxy- 
acetic acid was detected in integuments of the fruit as the intact molecule. 
Some regulators are used commercially to induce tomato plants to develop fruits by 
applying them to the flowers at the time of pollination. The fate of regulating compounds 
used for this purpose is now being studied. It is evident from the methods used com- 
mercially that application of the regulator to one flower cluster does not result in 
translocation of effective amounts of the compound from this treated cluster to untreate l 
ones. 
Regulating chemicals are also used commercially to prevent growth of vegetative 
buds on stored plants. As far as published information goes, research in this field has 
been directed mainly toward development of effective chemicals rather than a study of 
the fate of the compounds that are useful. 
THERAPEUTANTS 
Generally speaking, both antibiotics and synthetically produced therapeutants are 
readily absorbed by roots, stems, leaves, and fruits. Little is known concerning absorp- 
tion by flowers. Therapeutant translocation is associated with water transport. Moving 
upward mainly in the xylem, these compounds tend to accumulate in leaves and possibly 
in fruits soon after application to roots or stems (1, 3, 5, 21, 32,50, 51, 62). Thera- 
peutants translocated into leaves or directly absorbed by leaves are not readily re- 
translocated (11, 48). This translocation characteristic is true of most therapeutants 
used at disease-controlling concentrations. The amount absorbed by leaves can be 
enhanced to some extent with adjuvants (21, 23, 61). Thus metabolism of therapeutants 
within leaves and fruits is of particular interest. 
Application to Leaves 
Some antibiotics are apparently changed while still on the surface of leaves as 
indicated by loss of microbial activity. For example, the antibiotic pimaricin was almost 
184 
