constituents, however, since both induced growth regulation but the amounts involved 
in this reaction were not detectable. 
Other regulating compounds are only partially metabolized when moderate amounts 
are placed on leaves. Holley, et al. (22) reported, for example, that approximately 
30 percent of the 2,4-dichlorophenoxyacetic acid absorbed by bean plants was detected in 
an unchanged form. Partial metabolism of this and other regulators by several kinds of 
plants has also been observed (15, 20, 52). 
Weintraub, et al. (64), applying very small amounts of 2,4-D to the terminal buds 
of bean plants, found that this compound was metabolized into other compounds within a 
few days. Radioactive carbon originally in the regulator was detected in many kinds of 
plant constituents including acids, sugars, dextrins, starch, pectin, proteins, and cell-wall 
substances. Various investigators have shown that indoleacetic acid is broken down by 
oxidase enzymes of some plants, and that indolealdehyde and perhaps other products 
result (57, 59). 
Some regulating chemicals are changed so readily within the plant that it is difficult 
to recover the compound originally applied. Recently C1l4-tagged naphthalenelactamide 
was used to study the fate of a compound of this type. The amide was applied quantita- 
tively and spread evenly over the upper surface of bean leaves. Metabolism of the 
regulator was studied as itmovedfrom the leaves to other parts of the plant. After 2 days, 
midribs of the treated leaves were assayed to determine the presence of the original 
compound, naphthalenelactamide, and its reaction products. Petioles of the treated 
leaves and stems of the plants were also studied. 
Naphthalenelactamide was not detected in the main veins, petioles, or stems of 
plants. The main veins did contain, however, one detectable reaction product and this 
gave an Rf of 0.67 compared with 0.92 for the lactamide applied to the leaves. This 
initial reaction product was also detected in the petioles and the stems. However, two 
additional reaction products were also detected in the petioles and these gave widely 
different Rf values. The stems contained still a fourth compound that differed from the 
parent lactamide and all the other reaction products detected (44). 
It is thus evident that some regulating compounds at least may react almost com- 
pletely when applied in small amounts to leaves. The primary reaction product of 
naphthalenelactamide found in the leaves was further altered as it reached the petioles 
and stems. These results parallel those of others who found only metabolites of 2,4-D 
in roots while 2,4-D and its metabolites were found in stems (15, 20). 
Applied to Stems 
Regulating compounds appear to be more readily absorbed and translocated when 
applied to young parts of stems than when applied to relatively mature parts. For example, 
when equal amounts of I -tagged 2,4-dichloro-5-iodophenoxyacetic acid were applied 
to relatively mature bean stems near the soil level and to relatively immature parts of 
the stems several inches above the soil level, most radioactivity was detected in the root 
when the more distant immature part of the stem was treated (40). 
Metabolism of some growth-regulating chemicals has been studied following absorp- 
tion by detached segments of stems (60). Most of this research has been directed mainly 
toward an understanding of the reactions involvedwhena regulator induces cell elongation 
rather than an understanding of the overall fate of these compounds when applied to the 
aerial or underground parts of intact plants. 
Applied to Roots 
Regulating compounds have been used little as soiltreatments except experimentally. 
In considering the fate of some regulating compounds applied to the soil surface, Linder 
(29) and Muzik (53) found that 2,4-D was absorbed relatively near the surface of the soil. 
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