Absorption and Elimination of the Allelochemical MBOA by Weeds during Seedling Growth

6-Methoxy-2-benzoxazolinone (MBOA) is an allelochemical that is found in Poaceae and is generally associated with monocotyledon species. This compound is formed from the glycosylated form of 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (Gly-DIMBOA) by a two-stage degradation process. The MBOA detoxification capacity of two weed species, namely Echinochloa crus-galli and Lolium rigidum, and a resistant biotype of Lolium rigidum (SLR31) was studied both qualitatively and quantitatively. The product of metabolism is similar for both weed species. This finding indicates that these weeds probably metabolize xenobiotics by an identical route, since the product detected was the same in both cases. Kinetic studies on the absorption and translocation to the shoot showed differences in these processes depending on the species. The analysis of treated plants, which were subsequently transplanted to a growth medium without xenobiotic compound, showed that the weeds studied are capable of transmitting the previously absorbed compound to the medium by root exudation. The results show that this process is another defense mechanism of plants facing external threats.