Oxaziclomefone [OAC; IUPAC: 3-(3,5-dichlorophenyl)-1-methylethyl)-2,3-dihydro-6-methyl-5-phenyl-4H-1,3-oxazin-4-one] is a new herbicide recently released onto the market by Aventis, in Japan. OAC is very effective in controlling <i>Echinochloa</i> sp., a weed which is particularly prevalent in paddy fields and which can substantially reduce the yield of rice. OAC inhibits growth of graminaceous monocots but is relatively ineffective on most dicots. OAC was found to inhibit cell expansion in maize cell suspension cultures (CSCs) and roots within 8 h of exposure and has an ID<sub>50</sub> (inhibition dose) of ~ 7 nM. Cell expansion is promoted and regulated by turgor pressure, cell wall loosening and tightening. OAC did not reduce turgor pressure in maize CSCs or impede water transport across cell membranes. The herbicide did not promote the activity, apoplastic action or secretion of peroxidase, which can effect cell wall tightening by catalysing the formation of diferulate and di-isodityrosine. OAC did not inhibit the activity, action or secretion of XET, which may promote cell wall loosening via transglycosylation of xyloglucan chains. The herbicide did not reduce the consumption of extracellular ascorbate by maize CSCs, suggesting that OAC did not inhibit the formation of <sup>*</sup>OH (generated via the Fenton reaction which requires the presence of ascorbate) believed to cause polysaccharide scission and therefore effect cell wall loosening. OAC did reduce acid-dependent creep in methanol-killed maize silks (though not consistently) but not in methanol-killed celery petiole vascular bundles. OAC also reduced acid-dependent creep in frozen, thawed maize roots but again not consistently. However, OAC did inhibit the action of β-expansin (aqueously extracted from <i>Zea mays</i> pollen) on boiled maize silks and roots, assayed using an extensiometer. OAC may inhibit cell expansion by suppressing β-expansin-mediated cell wall loosening.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:660270 |
| Date | January 2002 |
| Creators | O'Looney, Nichola |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12719 |
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