s-Triazine Herbicides 
Degradation of c!4_ring -labeled simazine and 2-chloro-4-ethylamino -6 -isopropyla - 
mino-s-triazine [atrazine] in the corn plant (a tolerant species) is indicated by the early 
appearance of C1402 released to the atmosphere (24,41,42). Only traces, if any, of 
simazine or atrazine remained in the plant at time of harvest (41). Cell-free preparations 
from corn tissues release little or no CO2 when incubated with simazine (21), but the 
herbicide molecule was altered (21,24,48). Hydroxy simazine appears to be the first 
metabolic product in the degradation of simazine (24,30), Cell-free preparations from 
wheat, a simazine-susceptible plant, did not alter the structure of the herbicide (48), 
Studies with c!4_y+ing-labeled simazine show that both tolerant and susceptible 
species absorb the chemical. However, unaltered simazine either cannot be detected in 
the foliage of tolerant plants or is present only in very small amounts. The amount of 
nonmetabolized simazine, or biologically active C!4-labeled degradation products, which 
accumulates in oats, cucumber, cotton, and corn, is correlated with the relative suscepti- 
bility of the four species (13,52,53). Some degradation of the c1l4-labeled herbicide is 
indicated in cotton and cucumber as well as in corn since C!40, was released from all 
three species (14). Solvent extracts of oat and cotton tissues showed that measurable 
amounts of the absorbed simazine was metabolized. With intact plants most of the 
simazine which was metabolized appeared to be converted in the roots. Roots of the two 
species degraded approximately equal proportions of simazine. Differences in the rates of 
accumulation of the herbicide in leaves of the two species were closely correlated with 
differences in rates of transpiration (52,53). 
Chloro-substituted aliphatic acid herbicides 
Although there have been few published reports concerning the metabolic fate of the 
chloro-substituted aliphatic acids in plants, the available literature indicates that dalapon 
and trichloroacetic acid [TCA] are not readily metabolized in plants. No metabolic 
products of C!4-labeled TCA could be found incorn or peas four days after treatment (5). 
Similar experiments with corn and soybeans treated with cl4_labeled dalapon showed no 
evidence of metabolism of the herbicide, Four days after treatment, 99 percent of the 
applied radioactivity was recovered by extraction and identified as dalapon (6). Dalapon 
remains essentially nonmetabolized in plants for long periods, but some slow decomposi- 
tion is indicated by the release of C136 (from dalapon-C136) or the incorporation of Cl4 
(from dalapon-2-C14) into other compounds (21,22,23). 
Substituted phenylurea herbicides 
Ethanol extracts of leaves from bean plants treated with carbonyl-C!4-labeled 3- 
(p-chlorophenyl)-1,1-dimethylurea [monuron] contained two major radioactive compounds 
(17). One of the compounds was identified as unchanged monuron. The amount of monuron 
in the tissue decreased with time, The amount of the second compound increased. The 
unknown was considered to be a monuron complex since monuron was released by acid 
hydrolysis. Degradation of monuron in plants was suggested by the rapid reduction of 
radioactivity after the fourth day following treatment. 
Carbamates 
The lower limit of sensitivity of the analytical methods for isopropyl N-phenylcarba- 
mate | IPC] and isopropyl N-(3-chlorophenyl) carbamate [CIPC] is 0.05 p.p.m. Analyses 
conducted on crops receiving high rates of chemicals have not shown residues which 
exceeded this amount (25,26,27). Apparently, these N-phenylcarbamates do not retain 
their identity in treated plants. 
The failure to find unaltered IPC in treated plants stimulated a search for possible 
transformation products. Isopropyl N-hydroxy, N-phenylcarbamate (N-hydroxy-IPC) 
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