Dinitroaniline herbicides structures

A strong correlation between the parachor (P), a structurally derived property previously used by McGowan (1954) to calculate aqueous solubilities and partition coefficients, and Kom was first observed by Lambert (1967) for two classes of compounds, substituted phe-nylurea herbicides and homologs of dinitroaniline herbicides. The rationale for using... 

Root tips squashes were also used to examine the cross-resistance of the R biotype to other mitotic disrupters. Mudge gi al- (3) had previously shown that field applications of all of the dinitroaniline herbicides were ineffective in controlling the R biotype, and this was confirmed using root tip squashes as well (20). The phosphoric amide herbicide amiprophosmethyl also inhibits polymerization of tubulin into microtubules (21) and causes the same kinds of mitotic disruption as the dinitroaniline herbicides. The R biotype is also cross-resistant to this herbicide (20). Because the structure of amiprophosmethyl and trifluralin are quite different, it is likely that mechanisms of resistance based upon translocation and/or metabolism of herbicides is unlikely (but see 16 for an exception). 

Tubulin may be polymerized into microtubules ifl vitro by incubation of a relatively concentrated protein extract in the presence of GTP and high concentrations of dimethylsulfoxide (25). When extracts of the R and S biotypes were subjected to this protocol in the presence of the dinitroaniline herbicide oryzalin, only the R biotype formed recognizable microtubules whereas the S biotype formed only small fragments or ring-like structures that may be small aggregates of tubulin (Fig. 2). Both biotypes were able to form microtubules in the absence of oryzalin (23, 24). These data indicate that the tubulin of the R biotype is different than the tubulin of the S biotype in its sensitivity to dinitroaniline herbicides. 

These studies established that (a) the microtubules of the R biotype are hyperstabilized and (b) phenocopies of the R biotype in structure and in insensitivity to microtubule disrupters could be induced by treating the S biotype with taxol. From this, one could conclude that a major factor in dinitroaniline-resistance in Eleusine is the hyperstability, presumably caused by the novel 0-tubulin form in the R biotype. This does not eliminate the possibility that the binding of dinitroaniline herbicides is altered in the R biotype and we hope to investigate this possibility as well. 

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